Project Circuit Design

VHF Antenna Amplifier Circuit Using BFT66 Transistor

2011-05-22T14:11:00.000-07:00

Here’s a design circuit for very simple antenna amplifier electronic circuit project can be designed using this circuit diagram. This antenna amplifier electronic circuit can be used for a frequency range between 1 and 300MHz. This circuit antenna amplifier can be used for high frequency and VHF band (for radio and TV) and will provide a 22 dB gain. This antenna amplifier electronic project has a very low noise, under 1.6dB. This is the figure of the circuit;

This VHF, FM amplifier circuit is constructed based on the BFT66 transistor connected in common emitter connection. L1 coil has a 6uH value, but can be used any coil for high frequency (with a value between 5.6 to 6.8 u H). L2 coil is an air core type coil and it has 5-6 turns (10mm long and 5 mm diameter). For L2 coil can be used a 0.25 mm Cuem wire. The pcb of this circuit must be placed near the antenna, in a small metallic box. This VHF antenna circuit must be powered from a 12 volts DC power supply circuit, you can use a 12 volt battery, because the current consumption of this circuit is very low under 10mA. You can replace T1 transistor with some other UIF similar transistor type which have a very low noise factor.

SCR Inverter Circuit Using BSTC1026

2011-05-11T20:58:00.000-07:00

Here’s a design circuit for SCR inverter circuit that is build using BSTC1026. If device is too heavy or if there is a short at the output, this requires some kind of protection, on the input line, in the form of a fuse or similar. This is the figure of the circuit;

The transformer used is a 10Watt mains type with 6Vdc+6Vdc windings on the SCR side and a 110V+110V windings, in series, at the output. Efficiency is 50% and the ideal load is equivalent to a 22k resistor, 5Watt. Output waveform is vaguely sinusoidal at a frequency of 400Hz.

Logic Power Control Circuit for 78xx Regulator

2011-05-11T20:56:00.000-07:00

Logic power control of analog regulator can be useful in application where a digital circuit/controller need to control power source, such as in EEPROM programmer or other power controls. This is a circuit provide ON-OFF control for 78xx regulator using digital (TTL or CMOS) signal level. This circuit uses transistors in series with the 78XX regulator, which it’s base is controlled by logic level input. This is the figure of the circuit;

Electret Condenser Microphone Amplifier Circuit Using LM1458

2011-05-11T20:49:00.000-07:00

Here’s a design circuit for electret condenser microphone amplifier. using a LM1458 dual op amp Operational Amplifier IC. electret condenser microphone by bias circuit and preamp. The circuit takes the audio signal rom the condenser microphone and amplifier it, so you can use the microphone as the input to some device which wouldn’t normally accept microphone level signals (which are very low). This is the figure of the circuit;

This amplifier has an adjustable gain, which is performed via. R1 (a 1 Mega Ohm variable resistor). It controls the feedback of the LM1458 dual opamp, which in turn drive a LM1458 output IC.

Electronic Parts List:
Q1,Q2 – LM1458 transistor
R1,R2,R3 – 4.7k ohm resistor
R4, R5 – 10k ohm resistor
R6,R7 – 47k ohm resistor
C1, – 0.22uF ceramic capacitor
C2, – 1uF ceramic capacitor

MIC1 – electret condenser microphone
All resistors are 5 or 10 percent tolerance, 1/4-watt. All capacitors are 10 percent tolerance, rated 35 volts or higher.

Car Prevent Theft Circuit

2011-05-11T20:33:00.000-07:00

Here’s a design circuit for frequency modulation radio controlled anti-theft warning signal can be utilized with any vehicle having 6 – to 12-volt direct electric current power grid. The miniskirt VIRAL HAEMORRHAGIC FEVER frequency modulation sender is climbed on the vehicle at dark, when it is parked in the railcar porch or parking. This is the figure of the circuit;

The recipient CXA1019, an IC-based frequency modulation wireless mental faculty, which is freely uncommitted on the marketplace at a sensible damage, stays inside. The recipient is tuned up to the relative frequency of the sender. When the vector is on and the signs are experienced by frequency modulation receiving set, no sibilation sound is uncommitted at the recipient turnout. Thus transistor T2 (BC548) not to follow up. The outcome is the relay driver electronic transistor T3 has the forward nucleotide preconception via 10k resistance R5 and the relay race is excited. If an trespasser seeks to drive a machine and took him a couple of meters from the auto porch, the link between the railroad car (vector) and alert (recipient) broken.

Surround Sound Decoder Circuit

2011-04-08T12:04:00.000-07:00

This is a design circuit for an small surround sound decoder schematics. You may use this decoder surround sound systems for your home audio system. This is the figure of the circuit diagram;

The circuit’s operation starts as the stereo sound signal transports surround sound information on the master volume part of the circuit. This will drive the Left channel Lch attached to Model TL072 IC1A and IC1b in which Right channel Rch is attached. The outputs on these operational amplifiers would serve as the input buffer to the following stages of the circuit. IC2C is responsible for summing up the signals from the left and right channels that will power the central loudspeaker output while IC2D is responsible for increasing the phase difference between left and right channels which is encoded in the two channels and will be fed to the rear loudspeakers. It is necessary to ensure that the negative terminals between the rear speaker is not earthed because they will simply function in parallel with the main speakers.

The output of IC2D will power regulated delay unit of audio to the rear loudspeakers. This would lead to the creation of proper sense of spacing in accordance to the size of the room. This will incorporate op-amp sound delay signal IC5 MN3004 which has 512 stages. Since IC4 MN3101 is a clocking signal, it provides timing to IC5 as it functions as an oscillator in the circuit. Variable capacitor C17 regulates the delay time in the circuit. The presence of filters in the circuit is for the purpose of preventing noise that will be produced during the process. These filters can be regulated to cut the frequencies above 8 KHz and under 100 Hz, to be able to drive the rear speaker. The rear loudspeaker is small in size because its input is encoded with a bandwidth of 100 Hz up to 8 KHz. The filters are built around the IC6A/B which is also an output buffer. A potentiometer is placed in every output to aid in the adjustment and regulation of loudspeakers and amplifiers. The supplied power in the circuit is 15 V and every output can drive a single power amplifier.

Repeating Interval Timer Circuit

2011-04-08T11:58:00.000-07:00

This is a circuit for an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days and beyond. This is the figure of the circuit;

The output section is a simple Monostable Circuit. When Pin 6 of the Cmos 4001 is taken high - the monostable triggers - and the relay energizes. It will remain energized for a period of time set by C1 & R3.

With the values shown - R3 will provide output periods of up to about 30-minutes. However, you can choose component values to suit your requirements. For example, if you reduce R3 to 1meg - and C1 to 4.7uF - the maximum output period is between 3 and 5 seconds. Owing to manufacturing tolerances - the precise length of the time period available depend on the characteristics of the actual components you've used.

Periodic Timer Circuit

2011-04-08T11:47:00.000-07:00

This is a circuit for timer circuit that is similar to the 5 to 30 minute timer except that when switch S1 is closed, the on/off action of the circuit will continue indefinately until S1 is opened again. A 7555 time and low leakage type capacitor for C1 must be used. This is the figure of the circuit;

The 6 way rotary switch S3 adds extra resistance in series to the timing chain with each rotation, minimum resistance point "a" maximum point "f". The 7555 is wired as an equal mark/space ratio oscillator, the timing resistor chain R1 to R6, being connected back to the output of the timer at pin 3.The output pulse duration is defined as;

T = 1.4 R1 C1
This gives on and off times of about 379 seconds for postion "a" of S3 (just over 6 minutes), to about 38 minutes at point "f". The times may of coourse be varied by altering R1 to R6 or C1.

Basic Inverter Circuit

2011-04-08T11:41:00.000-07:00

Here’s a design circuit for the bacis of inverter circuit diagram. The circuit will convert 12V DC to 120V AC. This circuit can handle up to 1000Watts supply depends the T1, T2 and transformer used. This is the figure of the circuit diagram;

Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power. The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055′s in the parts list can only handle 15 amps each.

5 to 30 Minute Timer Circuit

2011-04-08T11:36:00.000-07:00

This is a design circuit for a switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps. This is the figure of the circuit;

Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also a low leakage type capacitor must be used for C1, and I would strongly suggest a Tantalum Bead type. Switch 3 adds an extra resistor in series to the timing chain with each rotation, the timing period us defined as :

Timing = 1.1 C1 x R1

Note that R1 has a value of 8.2M with S3 at position "a" and 49.2M at position "f". This equates to just short of 300 seconds for each position of S3. C1 and R1 through R6 may be changed for different timing periods. The output current from Pin 3 of the timer, is amplified by Q1 and used to drive a relay.

Static Detector Negative Ion Detector Circuit

2011-03-30T04:12:00.000-07:00

This is a design circuit for a sensitive detector for static electricity based around a single Field Effect Transistor It can also be used to detect the presence of negative ions, or test a negative ion generator. This is the figure of the circuit;

This circuit utilizes the extra high input impedance of a FET, and also demonstrates the gate terminals sensitivity to changes in voltage. The gate terminal here is left open circuit, connected only to the "probe". The probe is just a few inches of bare copper wire. With no fixed DC biasing, the gate terminal will respond to micro changes in voltage. This causes a current change in the drain circuit and the meter will indicate a charge or "field strength".

It is important not to make this circuit on vero board or PCB material as this will reduce the effective gate impedance. Instead use an "open" construction technique soldering each component together. The probe should not be touched directly and is best insulated in a plastic pen sleeve.

Pulse Width to Analog Voltage Demodulator Circuit

2011-03-30T03:57:00.000-07:00

This is a design circuit for a pulse width to analog demodulator circuit. This circuit is used to demodulate the pulse width to analog voltage level. This is the figure of the circuit;

Using input pulse width range of 0 to 1 microsecond, this circuit can produces Output range of 0 to 10 v. The input pulse is integrated and the final value is held until next pulse arrives. Then for next integration, the output return to zero.

Color Shifting LED Show Circuit

2011-02-10T07:23:00.000-08:00

This is a circuit that gives a changing-color LED display, where a LED will emit a dynamic shifting color, from red to green smoothly through yellow. The circuit uses NE556 dual timer, equal to two 555 IC but in only one package. The oscillators set at different frequencies. Here’s the figure of the circuit;

The high frequency (upper part) is used to construct a PWM signal, and the lower frequency oscillator is used to control the shifting frequency. What is done by the low frequency oscillator is no more than modulating the duty cycle (active factor) of the PWM. The PWM signal is generated by comparing a high frequency saw tooth-like signal with a slow varying reference. And two comparator is used to produce two complementary PWM signals. When the first PWM signal has (x) active factor, then the complement would have (1-x) active factor. In reality there is no yellow LED, but when the green and the red has 50% duty cycle then the combination would produce a yellow color. Since the PWM signal changes its duty cycle slowly from zero to 100%, the impression will look like the LED shifts its color smoothly from red to green back and forth.

200mA/Hour – 12V Ni-Cad Battery Charger Circuit

2011-02-10T07:17:00.000-08:00

This is a circuit of 12V Ni-Cad battery charger with charging rate of 200mA/Hour. Here’s the figure of the circuit;

This Ni-Cad battery charger circuit charges the battery at 75 mA until the battery is charged, then it reduces the current to a trickle rate. It will fully recharge a dead/unpowered battery in 4 hours and the battery can be left in the charger indefinitely. To set the shut off point, connect a 270 ohm / 2 Watt resistor across the charge terminals and adjust the pot for 15.5V across the resistor.

1.5V to 9V Battery Tester Circuit

2011-02-10T07:12:00.000-08:00

Here’s the design circuit of DC battery tester designed by Matthew B. This circuit can be used to measure DC battery from 1.5V up to 9V. This is the figure of the circuit;

It’s possible you have test with the values of R3 and R4 to have a precise reading from the meter. Every meter is different, so a little bit of experiencing using the resistor values is needed. Experiment with using a variable resistor instead of R3 & R4 to get a value of resistance that works.

Component Parts List:
R1 = 18K Ohm
R2 = 240 Ohm
R3 = 8.2K Ohm
R4 = 3K Ohm
R5 = 10 Ohm
M1 = Panel Meter (Anyone will work

Voltage Comparator Circuit

2011-01-27T06:32:00.000-08:00

This is a circuit of comparator circuit compares two voltage signals and determines which one is greater. The result of this comparison is indicated by the output voltage: if the op-amp's output is saturated in the positive direction, the non-inverting input (+) is a greater, or more positive, voltage than the inverting input (-), all voltages measured with respect to ground. If the op-amp's voltage is near the negative supply voltage (in this case, 0 volts, or ground potential), it means the inverting input (-) has a greater voltage applied to it than the non-inverting input (+). This is the figure of the circuit;

This behavior is much easier understood by experimenting with a comparator circuit than it is by reading someone's verbal description of it. In this experiment, two potentiometers supply variable voltages to be compared by the op-amp. The output status of the op-amp is indicated visually by the LED. By adjusting the two potentiometers and observing the LED, one can easily comprehend the function of a comparator circuit.

For greater insight into this circuit's operation, you might want to connect a pair of voltmeters to the op-amp input terminals (both voltmeters referenced to ground) so that both input voltages may be numerically compared with each other, these meter indications compared to the LED status:

Small DC Motor Speed Controller Circuit

2011-01-27T06:30:00.001-08:00

Electric motor has been widely used as motion control, and many type of motor controllers have been designed to provide variable speed drives for the motor. The best controller is the servo controller, where is a precise speed control is implemented using a speed sensor in the feedback path. The circuit of the motor controller is in this article use a novice method to control the motor. It uses the back electromotive force (back-emf) sensing to keep the motor rpm at a fairly constant value. This is the figure of the circuit;

his motor speed controller is suitable for 3V battery operated devices like portable cassette player or portable audio cd player, keeping the motor rpm to be constant. This circuit is not a PWM motor control, so the motor power should be low power type to avoid excessive heating. This circuit only works for small dc motor, it won’t work for ac motor. The motor driver at the final output is integrated in the IC chip, ideal for low component count solution. Unlike a servo controller, the motor speed is not kept at very tight reference because the feedback is not coming from a speed sensor, but only detect the dc motor’s electromotive force generation to maintain the motor speed at a fairly constant value. [Circuit diagram source: STMicroelectronics Application Notes]

Precision Voltage Follower Circuit

2011-01-27T06:29:00.000-08:00

This is a design circuit of the full voltage gain of the operational amplifier was available, resulting in the output voltage saturating for virtually any amount of differential voltage applied between the two input terminals. This is good if we desire comparator operation, but if we want the op-amp to behave as a true amplifier, we need it to exhibit a manageable voltage gain. This is the figure of the circuit;

If we connect the output of an op-amp to its inverting (-) input, the output voltage will seek whatever level is necessary to balance the inverting input's voltage with that applied to the non-inverting (+) input. If this feedback connection is direct, as in a straight piece of wire, the output voltage will precisely "follow" the non-inverting input's voltage. Unlike the voltage follower circuit made from a single transistor (see chapter 5: Discrete Semiconductor Circuits), which approximated the input voltage to within several tenths of a volt, this voltage follower circuit will output a voltage accurate to within mere microvolts of the input voltage!

Measure the input voltage of this circuit with a voltmeter connected between the op-amp's non-inverting (+) input terminal and circuit ground (the negative side of the power supply), and the output voltage between the op-amp's output terminal and circuit ground. Watch the op-amp's output voltage follow the input voltage as you adjust the potentiometer through its range

Potent Audio Amplifier Circuit Using TDA7294

2011-01-27T06:28:00.000-08:00

This is a design of Super Amplifier with tda7294 of the St micro eletronics, is possible to get potency of up to 100W in an only chip, for an unit stereo to use two same to that. That circuit is based on the datasheet of the ready to work with sources of strong signs, in case it is necessary it uses a pré-amplifier in the form of an op amp. This is the figure of the circuit;

That circuit type with integrated circuit is ideal for systems of involving sound. Because he is quite compact could use an independent amplifier for each one of the high speakers. In that way it can be to share the source dimensioned it is clear to support all the connected amplifiers. Oh you can remove a wave with that neighbor that bought a " home theater " of 1000W PMPO, and fear in saying that is an enormous potency, when in reality it will verify the real potency of the equipment it doesn't arrive nor to 10W RMS for channel. It already imagined a system of high active speakers with 80W.

Positive Low Voltage Hot Swap Controller Using Power Limiter

2011-01-27T06:27:00.000-08:00

This is the design circuit of Positive Low Voltage Hot Swap Controller circuit with Power Limiter. This circuit gives intelligent control of the power supply voltage to the load during removal and insertion of circuit cards from “hot” power sources or a live system backplane. This is the figure of the circuit;

This circuit uses The LM25069 that gives in-rush current control to limit system voltage transients and droop. This circuit has programmable current limit and power dissipation in the external series pass N-Channel MOSFET. So, operation will in the Safe Operating Area (SOA). The POWER GOOD output is used to indicate voltage is within 1.3V of the input voltage. this circuit has The programmable input under-voltage and over-voltage, programmable lockout levels and programmable hysteresis, programmable the initial insertion delay time and programmable fault detection time. The LM25069-2 automatically restarts at a fixed duty cycle, and LM25069-1 latches off after a fault detection. The LM25069 has 10 pin MSOP package. Refer to its datasheet for selecting the proper external components values that suits your need. [Circuit diagram source: National Semiconductor]

Positive High-Voltage Hot Swap Controller with Power Limiter

2011-01-27T06:25:00.000-08:00

This is the figure of the Positive High-Voltage Hot Swap Controller circuit with Power Limiter. This circuit uses the TPS2491 or TPS2490 because both of them have some advantages. The advantages of the TPS2491 and TPS2490 are positive high voltage, easy-to-use and has 10-pin Hot Swap Power Manager™ devices. 10-pin Hot Swap Power Manager™ devices will ensure the safety in driving an external N-channel MOSFET switch. This is the figure of the circuit;

TPS2491 and TPS2490 usually are used in electronic circuit breaker protection, interfacing to down-stream dc-to-dc converters, power feed protection inrush current limiting and controlled load turn-on. This circuit has the current limiter and power limiter. Both of them ensure that the external MOSFET operates inside a selected safe operating area (SOA) under the harshest operating conditions. Besides that, these devices are space-saving 10-pin MSOP package, available in a small and significantly reduce the number of external devices, saving precious board space. [Circuit diagram source: Texas Instruments Application Note]

Discrete Running Flashing LED Circuit

2010-08-14T17:14:00.000-07:00

This is a circuit for Discrete Running LEDs circuit. This circuit gives a chasing pattern like the running LEDs display in video shops. This is the figure of the circuit;

When the power is applied to this circuit, all transistors will try to come on at the same time. However, some will get a different turn-on current because of the exact value of the 22u electrolytics, and some will be faster due to their internal characteristics. The circuit start reliably because of the last 22u that delay the voltage-rise to the base of the first transistor. This circuit can be extended to any number of odd stages.

Infra Red Wireless Door Monitor Circuit

2010-07-24T01:47:00.000-07:00

This is a design circuit for door monitor project uses an infrared beam to monitor door & passageways or any other area. The principle operation of this circuit is when the beam is broken a relay is tripped which can be used to sound a bell or alarm. Suitable for detecting customers entering a shop, cars coming up a driveway, etc. The IR beam is very strong. Distances over 25 feet can be monitored. A 12VDC supply is required to power the circuit. A 12V wall adaptor is fine. Provision has been made so that only one power supply needs to be used to power both units. The relay is rated to switch mains voltages. This is the figure of the circuit;

The door monitor transmitter board consists of two square-wave oscillators, one running at approx. 250Hz and the other running at 38kHz. The 38kHz frequency acts as a carrier wave and is required by the IR receiver module on the receiver board. This carrier wave is “ANDed” or modulated by the 250Hz frequency to produce an output signal that contains bursts of 38kHz at a rate of 250Hz. This signal is used to drive an infrared LED. The oscillators are made by using two 555 timer ICs set up as “astable” (free running) multivibrators. IC1 is used for the 250Hz oscillator. Resistor R1 and R2 and capacitor C1 set the frequency. Another 555 chip, IC2, is used for the 38KHz oscillator. Resistors R4 and R5 and capacitor C3 set the frequency. Notice the diodes D1 and D3. This is the figure of the receiver circuit;

The door monitor receiver consists of an IR receiver module that detects the incoming IR beam from the transmitter. The IR signal is used to keep a capacitor charged which in turn holds a relay operated. When the beam is broken the capacitor discharges and the relay releases. An IR receiver/detector module, RX1, is made up of an an amplifier/filter circuit tuned to detect a 38kHz frequency. The output pin is low whenever a 38kHz signal is detected.

When the IR beam is present the relay is operated. Not all Receiver Modules are the same. IR decoder module looks for a manufacturer-specific leader code before it decodes the modulated signal. The door monitor project produces an NEC compatible Leader code. The Kodenshi PIC37043LM and PIC12043LO decoder modules are the ones that are used in this project. If you use the incorrect IR decoder module the relay will not be operated continuously but will drop out after less than a second after power is applied.

FM Phone Transmitter Circuit

2010-07-24T01:45:00.000-07:00

This circuit provides the schematic and the parts list needed to construct a FM Phone Transmitter. This device attaches in series to one of your phone lines. This is the figure of the circuit;

When there is a signal on the line (that is, when you pick up the handset) the circuit will transmit the conversation a short distance. In particular it will radiate from the phone line itself. It is a passive device - there is no battery. It uses the signal on the phone line for power. No aerial is needed - it feeds back the RF signal into the phone line which radiates it in the FM band. The frequency of transmission may be adjusted by the trimcap. Note that some countries may ban any electronic device which attaches to the telephone. It is the responsibility of the constructor to check the legal requirements for the operation of this FM Phone Transmitter and to obey them. The circuit is a radio frequency (RF) oscillator that operates around 93 MHz (93 million cycles per second). Power for the circuit is derived from the full wave diode bridge. C1, C8, L3 & T1 forms the FM oscillator.

Every Tx needs an oscillator to generate the Radio Frequency (RF) carrier waves. L1, C6, T2 forms the power amplifier. Audio from the telephone lines is coupled through R3 & C2 into the base of T1 to modulate the oscillator. This is done by varying the junction capacitance of the transistor. Junction capacitance is a function of the potential difference applied to the base of the transistor. R1 & C4 act as a low pass filter.

C3 is a high frequency shunt. L2 is call a RFC (radio frequency shunt.) It decouples the power and audio from the transmitter amplifier circuit. This type of circuit usually should be calibrated. The resonant frequency of the L1-C6 amplifier circuit should be adjusted to match the resonent oscillator frequency of C1, C9-L3. However, in practice, we think you will find that the unit operates perfectly OK as it is constructed without the need to calibrate anything. If you want to try calibration you will need a frequency meter, a CRO or just trial and error.

Calibrate by moving the coils of L1 further apart. With C1 at 27p you will find that the it tunes into the FM band in the 86 - 95 MHz area. With C1 at 22p the band is raised to about 90-95mhz (depending in the coil spacing.) If you want to move this tunable area still higher to over 100MHz range then replace C1 by a 15pF or 10pF capacitor. This assumes that the on-hook voltage is about the standard 48V. If the on-hook voltage of an extension phone network is lower, say about 39V, C1 will have to be lower in the 15p to 10p range to be in the commercial FM band in this case.

Note that you should not hold the printed circuit board physically in your hands if you try to do any calibration. Your own body capacitance when you touch it is more than enough to change the oscillation frequency of the whole unit. You can experiment the FM Phone Transmitter to get greater transmission range away from the phone line by adding an aerial (about 150 cm of 26 gauge wire) to the collector of T2.

Single Transistor Lead Acid Battery Monitor Circuit

2010-07-24T01:31:00.000-07:00

This is a design circuit that is a very simple battery monitor using a dual-color LED and a few additional components. When the red and green LEDs are illuminated, the LED produces orange. The following battery monitor circuit turns on the red LED below 10.5v. The green LED illuminates above 11.6v. The orange LED illuminates between 10.5v and 11.6v. This is the figure of the circuit;

This simple battery monitor circuit is suitable for your 12V lead acid car battery: simple indication of the battery health.

[Schematic circuit source: talkingelectronics.com].

Car LED Light Sequencer Circuit

2010-07-24T01:26:00.001-07:00

This is a design of Car LED Light Sequencer circuit uses a standard 74C164 8 bit shift register as its heart of operation. The 74C164 is also known as a 8-Bit Parallel-Out Serial Shift Register which is a monolithic complementary MOS (CMOS) integrated circuit. These 8-bit shift registers have gated serial inputs and clear. Each register bit is a D-type master/slave flip-flop. This is the figure of the circuit;

Data is serially shifted in and out of the 8-bit register during the positive going transition of clock pulse. Clear is independent of the clock and accomplished by a low level at the clear input. It has a wide supply voltage range from 3V to 15V DC. The input data goes to the serial inputs at pin 1 and 2 which are connected to VCC of the circuit. When pins 1 and 2 are high, the data moves one step forward with each clock pulse. As shown in the diagram above, the outputs are pins 3-6 and 10-13. The data flows from output 1 to 2 to 3... to 8 with each positive edge of the clock pulse. The data can be cleared to zero by putting a momentary low input at pin 9.

12V Battery Charger for Sealed Lead Acid Circuit

2010-07-24T01:00:00.000-07:00

This circuit is design for battery charger circuit that is for 12V Seales Lead Acid (SLA) battery. It is actually a half-wave rectifier. It only charges the battery on every half cycle. The plug pack doesn’t like this as it leaves residual flux in the core of the transformer and causes it to overheat. This is the figure of the circuit;

Firstly, these batteries must be charged, discharged and stored very carefully.We normally think batteries can be stored for months (if not years) and they will be available for immediate use. This is not the case with SLA batteries. If you store a NEW, full charged SLA battery for 6 months or more, you will find it may be fully discharged. You may also find you cannot charge it!! It may be worthless. That’s how delicate SLA batteries are.

They must be charged on a regular basis to prevent them discharging to a very low voltage level. If the terminal voltage of a SLA battery is allowed to go below 8v, a process called SULPHATION starts to cover the surface of the plates and prevents the battery being re-charged. The internal resistance of the battery increases and it becomes useless.

Animated LED for Bike Turning Signal Circuit

2010-06-27T08:34:00.000-07:00

In this circuit, we can make animated LED for bike turning signal. The Led will blink from the right (LED 1) to the left side (LED 5). This is the figure of the circuit;

You must build the second unit to give the complete left and right t urn signal. For the right turn signal, arrange the LEDs so they blink from the left to the right side.

AC Power Supply Low Voltage

2010-06-21T23:15:00.000-07:00

This is AC power supply circuit with low voltage output (step down transformer converter). Warning! This project involves the use of dangerous voltages. You must make sure all high-voltage (120 volt household power) conductors are safely insulated from accidental contact. No bare wires should be seen anywhere on the “primary” side of the transformer circuit. Be sure to solder all wire connections so that they’re secure, and use real electrical tape (not duct tape, scotch tape, packing tape, or any other kind!) to insulate your soldered connections.

If you wish to enclose the transformer inside of a box, you may use an electrical “junction” box, obtained from a hardware store or electrical supply house. If the enclosure used is metal rather than plastic, a three-prong plug should be used, with the “ground” prong (the longest one on the plug) connected directly to the metal case for maximum safety.

Before plugging the plug into a wall socket, do a safety check with an ohmmeter. With the line switch in the “on” position, measure resistance between either plug prong and the transformer case. There should be infinite (maximum) resistance. If the meter registers continuity (some resistance value less than infinity), then you have a “short” between one of the power conductors and the case, which is dangerous!

Next, check the transformer windings themselves for continuity. With the line switch in the “on” position, there should be a small amount of resistance between the two plug prongs. When the switch is turned “off,” the resistance indication should increase to infinity (open circuit — no continuity). Measure resistance between pairs of wires on the secondary side. These secondary windings should register much lower resistances than the primary. Why is this?

Plug the cord into a wall socket and turn the switch on. You should be able to measure AC voltage at the secondary side of the transformer, between pairs of terminals. Between two of these terminals, you should measure about 12 volts. Between either of these two terminals and the third terminal, you should measure half that. This third wire is the “center-tap” wire of the secondary winding.

Twisted Pair Video Cable Driver and Receiver Circuit

2010-06-21T23:11:00.001-07:00

Twisted-pair wiring is a wiring technique that usually used for in-building data communication. Compared to conventional coaxial-cable, this technique offers substantial cost saving, for video transmission on the same medium. A differential driver is used to launching a baseband camera signal to twisted pair. Twisted pair exhibits a roll-off characteristic is that need equalization to correct for. The differential driver and the corrector circuit. This is the figure of the circuit;

This differential driver uses two LT6652, one is used to create a gain of +1 and another is used to make a gain of–1. Besides that, LT6652 is used to reject any ground noise and prevent ground loops via the coax shield. The signal is terminated and re-amplified to re-create an unbalanced output for connection to recorders, display monitors, etc when the signal at the receiving end of the cable. The amplifier must provide the 2x gain required output drive and make up for the losses in the cable run.

[Circuit source: Linear Technology Application Notes]

Stand Alone 600mA Li-ion Battery Charger Circuit

2010-06-21T23:09:00.001-07:00

A constant-current/constant-voltage linear charger for single-cell lithium-ion (li-ion) can be constructed using only a tiny battery charger controller chip EUP8054 and a few passive components. This tiny integrated circuit chip is suitable for various portable devices. This controller chip is also compatible with USB power specification, ideal for charging the battery when the device is plugged to USB port. This is the figure of the circuit;

External sense resistor is not needed since the MOSFET internal architecture has accommodated this function. During high power operation or high temperature, a thermal feedback regulates the charge current to limit the die temperature. The charge voltage is fixed at 4.2V, and the charge current is adjustable via an external resistor. The controller chip automatically terminate the charging cycle when the charging current drops to 1/10th of nominal programmed value after the final float voltage is reached. The controller automatically enter low current state when the input supply is removed, draw less than 2uA current from the battery.

Solar Powered Garden Lamp Circuit with Light Sensor

2010-06-21T23:07:00.001-07:00

This is a reverse engineered circuit diagram of yet another commercially produced solar garden lamp. To turn the light on at night, this depends upon a CDS photocell. It allows the battery to charge more efficiently although more complex than the circuits. This is the figure of the circuit;

If you want to read more original source, you can visit this link:
http://members.shaw.ca/novotill/SolarGardenLight/index.htm

Closed Loop Automatic Power Control for RF Applications Circuit

2010-06-21T22:59:00.000-07:00

This is a circuit design of Closed-Loop Automatic Power Control for RF Applications. The circuit uses a log detector (AD8318) and a VGA (ADL5330). This circuit has high temperature stability because of the high temperature stability of the AD8318. The AD8318 also ensures the same level of temperature stability at the output of the ADL5330 VGA.

The ADL5330 is converted from an open-loop variable gain amplifier into a closed-loop output power control circuit by the log amp detector. The POUT vs. The set point transfer function of AD8318 follows a linear-in-dB characteristic because the AD8318 has a linear-in-dB transfer function. This is the figure of the circuit;

A sample of the output RF must be fed back to the detector by using additional attenuation and a directional coupler to operate the ADL5330 VGA in an AGC loop. A DAC is used to apply A setpoint voltage to the VSET input of the detector. The VOUT is connected to the GAIN pin of the ADL5330. The GAIN voltage is adjusted by the detector until the level at the RF input corresponds to the applied setpoint voltage. The correct balance between the setpoint voltage and the input signal level at the detector is set by the GAIN.
[Circuit source: Analog Devices Application Note]

Triangular-Wave Generator Circuit

2010-05-18T07:16:00.001-07:00

This is a circuit for a constant amplitude triangular-wave generator. A variable frequency triangular wave whose amplitude is independent of frequency is provided by this circuit. This circuit is based on LM101. This is the figure of the circuit;

As a reset circuit, the generator embodies an integrator as a ramp generator and a threshold detector with hysteresis. There is no further explanation is needed because the integrator has been described in a previous section. It’s a latch circuit with a large dead zone, on that case, the threshold amplifier detector is similar to a Schmidt Trigger. By using positive feedback around an operational amplifier, we can implement this function. The positive feedback network provides a voltage at the non-inverting input which is determined by the attenuation of the feedback loop and the saturation voltage amplifier when the amplifier output is in either the positive or negative saturated state. The voltage at the input of the amplifier must be caused to change polarity by an amount in excess of the amplifier input offset voltage to cause the amplifier to change states. When this is done, until the voltage at its input again reverse, the amplifier saturates in the opposite direction and remains in that state. By examining the operation with the output of the threshold detector in the positive state, the complete circuit operation may be understood. To cause a current I+ to flow, we have to apply the detector positive saturation voltage to the integrator summing junction through the combination R3 and R4.

Then, a negative-going ramp with a rate of I+/C1 volts per second until its output equals the negative trip point of the threshold detector is generated by the integrator. After that, at the integrator summing point , the threshold detector changes to the negative output state and supplies a negative current, I-. A positive-going ramp with a rate of I-/C1 volts per second is generated by the integrator until its output equals the positive trip point of the threshold detector where the detector again changes output state and the cycle repeats. R3, R4, C1, and the positive and negative saturation voltages of the amplifier A1 determine the triangular-wave frequency. Amplitude is determined by the threshold detector saturation voltages and the ratio of R5 to the combination of R1 and R2. If the detector has equal positive and negative saturation voltages, positive and negative ramp rates are equal and positive and negative peaks are equal. If the inverting input of the threshold detector, A1, is offset with respect to ground, the output waveform may be offset with respect to ground. If the detector is clamped with matched Zener diodes as shown in following figure, the generator may be made independent of temperature and supply voltage. If power supply impedance causes oscillation during its transition time, the detector may be compensated and the integrator should be compensated for unity-gain. For maximum symmetry, the current into the integrator should be large with respect to Ibias and offset voltage should be small with respect to Voutpeak.

[Schematic circuit source: National Semiconductor Application Note]

The Heartbeat Sensor (Transducer) Circuit

2010-05-18T07:13:00.000-07:00

This is a design circuit for heartbeat sensor circuit. To build a heart-beat transducer not as difficult as imagined. This is one design for simple heat sensor. This is the figure of the circuit;

This circuit made from an infrared phototransistor and infrared LED. This transducer works with the principle of light reflection, in this case the light is infrared. The skin is used as a reflective surface for infrared light. The density of blood in the skin will affect on the IR reflectivity. The pumping action of heart causes the blood density rises and falls. So that we can calculate the heart rate based on the rise and fall of intensity of infrared that reflected by skin.

Single Input to Differential Input Adapter for Digital Voltmeter Circuit

2010-05-18T07:10:00.001-07:00

In some cases, a differential input is needed for voltage measurement. Using the only one operational amplifier, you can build an adapter to provide a floating input for your ground-referenced voltmeter. This is the figure of the design voltmeter;

Use 1% tolerance metal film resistor for R1 and R2. Adjust VR1 to give zero voltage output when the input probe is shorted. You can use voltage supply +Ub and -Ub between 3 to 20V, as long as it is a symmetric supply.

Linearized Platinum RTD Signal Conditioner Circuit

2010-05-18T07:08:00.000-07:00

The best choice for stability and high accuracy in temperature measurements is Platinum resistance temperature detectors (RTD). However, the signal conditioning is complicated by the RTD which exhibit a non-linear temperature versus resistance characteristic. The non-linearity amount of 0 C to 100 C is up to 0.4 C. This is the figure of the circuit for Linearized Platinum RTD Signal Conditioner;

This circuit use A1 as a negative gain inverter to drive a constant current across the platinum sensor. The current reference is provided by the 1oK resistor and LT1009. The self heating induced errors reduced and the voltage through the RTD is low because A1 operates at negative gain. The platinum sensor’s temperature varies A1’s output potential and fed to A2.

The offsetting and scaled gain are provided by A2. Therefore, the A2’s output will swing 0.00V to 10.000V for 0.00 C to 100.00 C temperature swing at the RTD. The noise pick-up is limited by the 1uF capacitor. Returning a small portion of the circuit’s output to A1 will correct the 0.4 C non linearity error due to the RTD’s imperfect response. This circuit is calibrated by substituting the sensor with a precision decade box. The deviation of the each sensor is different depends on the manufacture that produced it. The purity of the material fix the gain slope of the platinum.

[Schematic circuit source: Linear Technology Application Note]

Adjustable High Power LED Driver Circuit

2010-05-18T07:03:00.000-07:00

This is a circuit that can drive three to four high power LEDs is shown on figure below. The ADP 1610 is an adjustable boost regulator. The voltage headroom and current for the LEDs is provided by this device. An average gain of 12 feedback network that servos the Rset voltage and the ADP1610 FB pin 1.2 V band gap reference voltage is formed by the AD5228 and the op amp. The voltage across Rset is regulated around 0.1 V and adjustable by the digital potentiometer as the loop is set. This is the figure of the circuit;

I led = Vrset/Rset

To conserve power but large enough to limit maximum LED current, Rset should be small enough. To limit the LED current within an achievable range, R3 should also be used in parallel with AD 5228. By lowering the R2 to R1 ratio as well as changing R3 accordingly, a current adjustment range can be expanded.

[Circuit source: Analog Devices Application Note]

Ni Cad Charger Circuit with Thermal Control

2010-05-15T05:05:00.001-07:00

This is a design circuit for Ni-Cad battery charger circuit that is using thermal control. This circuit is use LT1001 single op amp for main components. This is the figure of the circuit;

Ni Cad batteries can be charged at high current rates because it allows short charge time. But, it has difficulty in operations such as excessive internal heating degrades the batteries and can cause gas venting to the outside atmosphere. Because cell voltage is not necessarily indicative of the charge state of the battery , schemes based on monitoring cell voltage during charge surfer. For ambient temperature and battery characteristic shifts over life, open loop techniques involving high charge rates for a fixed time do not account. Measure cell temperature and taper the charge accordingly is one way to charge batteries fast without abuse. The figure below shows thermocouple usage for this function. The effects of ambient temperature is made zero by the second thermocouple. The low level capability necessary to work with the microvolt level thermocouple signals is furnished by LT1001. Assume a discharged battery pack in the Darlington collector line to understand the circuit’s operation.

The ambient thermocouple and battery are at the same temperature. The battery thermocouple is directly mounted to one of the cells in the pack. Expose the ambient thermocouple to ambient temperature and mounted to thermal mass which approximates that of the battery pack. Under these condition, the positive input is at zero volts and the thermocouple voltages cancel. The swing of amplifier which is made the Darlington pair turning on is caused by the negative current through the 620Kohm resistor to the summing junction. From the 15V supply, through the battery pack and to ground via the 0.6Ohm shunt is the way of current flow. The voltage across the shunt increases to 1V, balancing the summing junction, and about 1.6A controlled by amplifier servo through the battery pack. It heats as the battery charges. The battery-mounted thermocouple takes this heat. The voltage which appears at the amplifier’s positive input is determined by the temperature difference between the two thermocouples. This small negative voltage (1′C difference between the thermocouples equals 40uV) becomes larger as battery temperatures rises. The current greatly reduced through the battery by the amplifier which is operate at gain of 4300 to maintain its inputs at balance. The battery charges at a high rate until heating occurs and the circuit then tapers the charge. The value given in the circuit limit the battery surface temperature increase over ambient to about 5′C.

[Circuit source: Linear Technology Notes]

MAX6650 Fan Speed Controller Circuit

2010-05-15T05:02:00.000-07:00

This is a design circuit for fan speed controller circuit that is used MAX6650. The MAX6650 is designed to control a single fan. The MAX6651 has more features, it can controls a single fan and can monitor and watchdog three additional fan tachometer outputs. We can synchronize multiple MAX6651s to control multiple fans. The IC extensive programmability to accommodate a variety of fan speeds and types is included. This is the figure of the circuit;

Take a note that from the circuit on figure below, the MAX6650/MAX6651 are designed to be used with an external pass transistor. Since the output stage of the MAX6650/MAX6651 is an analog DAC and amplifier combination, feedback is taken from the drain of the transistor to the terminal on the IC labeled “FB”. Local feedback is required by this DAC/amplifier combination. The tachometer signal of the fan is actually the feedback complete loop, and this also returned to the MAX6650/MAX6651. The fan will be driven by these device until that tacho signal matches the programmed period in the speed register in the MAX6650/MAX6651.

[Circuit source: MAXIM Application Notes]

Low Drop-Out (LDO) Voltage Regulator Circuit

2010-05-15T05:00:00.001-07:00

This is a circuit for measuring low drop out circuit. This circuit is using one op amp for controller the circuit. This is the figure of the circuit;

There are several integrated circuit chips designed specially for LDO (low drop out) voltage regulator. Building LDO using standard op-amp and discrete components can be an alternative.

Crystal Oscillator Reference Circuit

2010-05-14T06:30:00.001-07:00

This is an illustrate a reference design for a crystal oscillator using the LMK04000 family. This oscillator circuit is implemented on the LMK04000 family evaluation board. This is the figure of the circuit;

The tuning diode is a Skyworks model SMV1249-074LF. It is a dual diode package in a common cathode arrangement. This diode configuration has the advantage of blocking reverse leakage current. The loop filter components are chosen to achieve a narrow loop bandwidth, in the range of 10 Hz to 20 Hz. The actual component values will depend on the parameters chosen for PLL1 (R divider and N divider values) and the slope of the crystal tuning curve. An initial estimate of the slope of the tuning curve can be developed using Equation (3) and the appropriate parameters from the crystal data sheet. Also note that Equation (4) should be substituted for CL in Equation (3).

A nominal value of 6 pF can be used for CIN. A reasonable range of values that can be used for CSTRAY is 2 pF to 4 pF. After the actual oscillator circuit has been implemented on a printed circuit board, the tuning curve should be measured to verify that the original estimate of the tuning slope was correct. Any significant difference may require recalculation of the loop filter components to maintain the desired loop bandwidth.

[Circuit source: National Semiconductor Notes]

Couple MIMO Transceiver Reference Clocks Circuit Using MAX2470

2010-05-14T06:29:00.001-07:00

This is a block diagram for the basic operation of MAX2470. This IC can use for transceiver reference clocks circuit. This is the figure of the block diagrams;

Ideal for discrete and module-based VCO designs, the MAX2470/MAX2471 are flexible, low-cost, high reverse-isolation buffer amplifiers. Both feature differential 50W outputs for driving a single differential (balanced) load or two separate single-ended (unbalanced) 50W loads. The MAX2470 offers a single-ended input and has two selectable frequency ranges of operation: 10MHz to 500MHz and 10MHz to 200MHz. The MAX2471 offers a differential input and operates from 10MHz to 500MHz. The MAX2470 operates from a single +2.7V to +5.5V supply. At -5dBm output power, it consumes 5.5mA in the high-frequency range and only 3.6mA in the low-frequency range. The MAX2471 operates from a +2.7V to +5.5V single supply and consumes 5.5mA.

[Circuit diagram source: MAXIM Semiconductor Notes]

Cellular Phone Calling Detector Circuit

2010-05-14T06:27:00.000-07:00

This circuit is designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED. This circuit is based on 7555 CMOS single chip IC. This is the figure of the circuit;

The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call. The signal detected by the sensor coil is amplified by transistor Q1 and drives the mono stable input pin of IC1. The IC's output voltage is doubled by C2 & D2 in order to drive the high-efficiency ultra-bright LED at a suitable peak-voltage. Stand-by current drawing is less than 200µA, therefore a power on/off switch is unnecessary. L1 can be made by winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Remove the coil from the former and wind it with insulating tape, thus obtaining a stand-alone coil. IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less. Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type is a very good choice.

Part:

R1____________100K 1/4W Resistor

R2______________3K9 1/4W Resistor

R3______________1M 1/4W Resistor

C1,C2_________100nF 63V Polyester Capacitors

C3____________220µF 25V Electrolytic Capacitor

D1______________LED Red 10mm. Ultra-bright (see Notes)

D2___________1N5819 40V 1A Schottky-barrier Diode (see Notes)

Q1____________BC547 45V 100mA NPN Transistor

IC1____________7555 or TS555CN CMos Timer IC

L1_____________Sensor coil (see Notes)

B1_____________1.5V Battery (AA or AAA cell etc.)

Hysteretic Constant Frequency Buck Regulator Circuit Using the LM5007

2010-03-30T14:05:00.001-07:00

This is a design circuit for frequency regulator circuit. This circuit is based on LM5007 for control the operation of the circuit. This is the figure of the circuit;

The LM5007 buck regulator differs in operation from other conventional control methods, such as fixed frequency current-mode, fixed on-time voltage mode, variable on-time, and variable off-time. The LM5007 hysteretic constant frequency control method offers better performance with smaller output capacitance and no loop compensation. The LM5007 is a high voltage IC designed to accept an input voltage of 9V - 75V (80V max). The bootstrap diode and high voltage N-Channel MOSFET buck switch are integrated in the IC, making the LM5007 attractive for applications where board space is at a premium.

The current loop formed by D1, L1, and C2 should be as small as possible. The ground connection from C2 to C1 should be as short and direct as possible. If the internal dissipation of the LM5007 produces excessive junction temperatures during normal operation, good use of the PC board’s ground plane can help considerably to dissipate heat.

[Circuit schematic source: National Semiconductor Notes]

Electronic Thermometer Circuit

2010-03-30T14:03:00.001-07:00

This is an electronic thermometer using an inexpensive silicon transistor as the temperature sensor. This circuit is based on LM112 op amp. This is the figure of the circuit;

This circuit can provide better than 1§C accuracy over a 100§C range. The emitter-base turn-on voltage of silicon transistors is linear with temperature. If the operating current of the sensing transistor is made proportional to absolute temperature the non-linearly of emitter-base voltage can be minimized. Over a b55§C to 125§C temperature range the non-linearly is less than 2 mV or the equivalent of 1§C temperature change. An LM113 diode regulates the input voltage to 1.2V. The 1.2V is applied through R2 to set the operating current of the temperature-sensing transistor. Resistor R4 biases the output of the amplifier for zero output at 0§C. Feedback resistor R5 is then used to calibrate the output scale factor to 100 mV/§C. Once the output is zeroed, adjusting the scale factor does not change the zero.

[Circuit source: National Semiconductor Notes]

Dual-Output Gate-Driver Approach Using the LM25037 Controller

2010-03-30T13:58:00.000-07:00

This is a design circuit for basic schematic of the LM25037 dual gate driver switching the gates of two FETs independently. This is the figure of the circuit;

Switching two independent FETs from a dual gate drive controller typically allows the designer to select low RDSON FETs with a higher gate charge. Higher gate-charge FETs tend to be less expensive than their lower gate-charge counterparts. The two FETs selected to be switched independently are the SiR468DP. As previously mentioned, driving two FETs in parallel produces a 50% reduction in RDSON. Switching FETs independently, however, no longer yields the 50% reduction in RDSON but transitional losses are reduced.

[Circuit source: National Semiconductor Application Notes]

Single Gate-Drive Parallel-FET Approach Using the LM5020 Controller

2010-03-30T13:50:00.000-07:00

Considering the previously-identified specification, the designer may opt to use National’s LM5020 PWM controller. This is a design for application from LM5020. This is a single gate driver parallel FET circuit. This is the figure of the circuit;

Placing two FETs in parallel will increase switching losses as the gate charge will double and therefore switching transition times will double. With high RMS switch currents and the doubling of gate charge, it is essential to select FETs that have a low RDSON and a low gate charge. These types of FETs tend to be more costly than FETs that have similar RDSON with a higher gate charge. To address this transitional loss issue, the FET selected for this example is the SiR472DP FET from Vishay.

[Schematic circuit source: National Semiconductor Notes]

Amplifier Biasing Circuit for Constant Gain with Temperature

2010-03-30T13:47:00.001-07:00

This is a circuit for amplifier circuit. But, this circuit has function for biasing the amplifier in temperature system. This circuit is based on LM114. This is the figure of the circuit;

In the circuit, a differential amplifier with the current source biased by an LM113. Since the LM113 supplies a reference voltage equal to the energy band gap of silicon, the output current of the 2N2222 will vary as absolute temperature. This compensates the temperature sensitivity of the trans-conductance of the differential amplifier making the gain temperature stable. Further, the operating current is regulated against supply variations keeping the gain stable over a wide supply range. As shown, the gain will change less than two per cent over a b55§C to a125§C temperature range. Using the LM114A monolithic transistor and low drift metal film resistors, the amplifier will have less than 2 mV/§C voltage drift. Even lower drift may be obtained by unbalancing the collector load resistors to null out the initial offset. Drift under nulled condition will be typically less than 0.5 mV/§C.

[Schematic circuit source: National Semiconductor Notes]

2V Low Voltage Regulator Circuit

2010-03-30T13:35:00.001-07:00

This is a design circuit for voltage regulator. This circuit is based on LM108 National Semiconductor Op Amp. This is the figure of the circuit;

The 2V voltage regulation which will operate on input voltages of only 3V. An LM113 is the voltage reference and is driven by a FET current source, Q1. An operational amplifier compares a fraction of the output voltage with the reference. Drive is supplied to output transistor Q2 through the Va power lead of the operational amplifier. Pin 6 of the op amp is connected to the LM113 rather than the output since this allows a lower minimum input voltage. The dynamic resistance of the LM113 is so low that current changes from the output of the operational amplifier do not appreciably affect regulation. Frequency compensation is accomplished with both the 50 pF and the 1 mF output capacitor.

[Circuit source: National Semiconductor Notes]

Boost Converter Circuit During The D and (1-D) Switching Period

2010-03-30T13:24:00.000-07:00

A higher-power boost converter often requires special consideration to minimize power losses and temperature rise in the FETs, diode, and inductor. Regarding FETs, many designers opt to place FETs in parallel to reduce conduction losses. This is a design circuit for the converters. This is the figure of the circuit;

The boost converter supplies a voltage that is always greater than its source voltage. The volt-second balance of the inductor L, for the D period, is added to the input voltage during the (1-D) period and is rectified to the output through the diode. The longer the D period, the shorter the 1-D period becomes, thereby increasing the voltage during the off time in order to maintain volt-second balance.

Circuit source: National Semiconductor Notes

Electric Field Disturbance Monitor Circuit

2010-03-29T13:40:00.000-07:00

This is a complete schematic diagram for electric field disturbance monitor circuit. This circuit is control based on LM662 op-amp. This is the figure of the circuit;

If you want to see more details, you can see from the source.

[Schematic source: Hobby Projects Application Notes]

WLAN Reference Design Circuit with the MAX2830

2010-03-29T13:31:00.002-07:00

This is design circuit for WLAN. This circuit is based on MAX2830. This is the figure of the circuit;

This reference design is a complete RF front-end solution designed to meet the WLAN IEEE® 802.11b/g standard. Using the MAX2830 RF transceiver, the design is capable of accommodating full range of 802.11g OFDM data rates (6, 9, 12, 18, 24, 36, 48, and 54Mbps) and 802.11b QPSK data rates (1, 2, 5.5, and 11Mbps). This solution offers high performance, small size, and low BOM cost. The features of this circuit is High-Performance Rx NF <>

Siren Driver Circuit Based on MOSFET

2010-03-29T13:27:00.000-07:00

This is a driver circuit for siren. This circuit usually used for car alarms. To build this circuit, we use VD-MOS FETs. This circuit receives 12 v supplies from battery. A microprocessor sends complementary pulse waveforms to the driver circuit as inputs. This is the figure of the circuit;

This circuit uses two PHC21025 which each of them contains two FETs. Two BSN20 VD-MOS FETs in small SOT23 packages also used in this circuit. The maximum configuration of this circuit needs eight components and the minimum configuration of this circuit needs six components.
[Schematic circuit source: NXP Notes]

Digital PLL Synthesis System

2010-03-29T13:22:00.000-07:00

Digital tuning systems are fast replacing the conventional mechanical systems in AM/FM and television receivers. A simplified block diagram of a typical digitally tuned receiver is shown in the figure.

Notice this receiver could be one for AM, FM, marine radio, or television; it makes no difference. The frequency synthesizer block generates the local oscillator frequency for the receiver, just as a conventional mechanical tuner would. However, the phase-locked-loop (PLL) acts as an integral frequency multiplier of an accurate crystal controlled reference frequency while the mechanical type provides a continuously variable frequency output with no reference. Some method of controlling the value of the multiplier for channel tuning must be provided. The other RF, IF, and audio/video circuitry will be the same as in the mechanical tuning method. [Diagram source: National Semiconductor Notes].

TSH22 Audio Line Driver Circuit

2010-03-12T18:59:00.001-08:00

This is an audio line driver circuit using a TSH22. The advantages of this circuit are low distortion, exhibits a wide bandwidth and an output current sufficient to drive medium impedance loads at a high level modulation. This is the figure of the circuit;

This circuit uses two TSH22 that is used in non inverting mode. The gain of this circuit can be set by resistors. This circuit only uses a single power supply with voltage between 8V and 30V. A phantom ground at VCC/2 is made by two resistors (R4 and R6).

Following equations show the overall gain for frequency in the bandwidth :
Gain channel 1 = (R1 + R2)/R1
Gain channel 2 = (R8 + R9)/R8
[Circuit Schematic Source: STMicroelectronics Application Note]

Digital Step Km Counter Circuit

2010-03-12T18:57:00.000-08:00

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking. A beeper (excludable), signals each count unit, occurring every two steps.

A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on. For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. This is the figure of the circuit.

IC1A & IC1B form a mono stable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each mono stable count. Q1 drives the piezo sounder and SW2 allows to disable the beep.

Part:
R1,R3____22K 1/4W Resistor
R2________2M2 1/4W Resistor
R4________1M 1/4W Resistor
R5,R7,R8__4K7 1/4W Resistor
R6_______47R 1/4W Resistor
R9________1K 1/4W Resistor

C1_______47nF 63V Polyester Capacitor
C2______100nF 63V Polyester Capacitor
C3_______10nF 63V Polyester Capacitor
C4_______10µF 25V Electrolytic Capacitor

D1_______Common-cathode 7-segment LED mini-display (Hundreds meters)
D2_______Common-cathode 7-segment LED mini-display (Kilometers)

IC1______4093 Quad 2 input Schmitt NAND Gate IC
IC2______4024 7 stage ripple counter IC
IC3,IC4__4026 Decade counter with decoded 7-segment display outputs IC

Q1,Q2___BC327 45V 800mA PNP Transistors

P1_______SPST Pushbutton (Reset)
P2_______SPST Pushbutton (Display)

SW1______SPST Mercury Switch, called also Tilt Switch
SW2______SPST Slider Switch (Sound on-off)
SW3______SPST Slider Switch (Power on-off)

BZ_______Piezo sounder

B1_______3V Battery (2 AA 1.5V Cells in series)

HI-FI Tone Control Circuit (High Z Input)

2010-02-26T19:00:00.000-08:00

This is a design circuit for Hi-Fi tone control circuit. This circuit is used for Hi-Fi tone control in amplifier. This is the figure of the circuit.

To buffer op-amp operated feedback type tone control circuit, this circuit uses 2N3684 JFET. The 2N3684 JFET is implemented on this circuit because it has low noise characteristics and provides the function of a high input impedance. [National Semiconductor Application Note]

100Watt Inverter Circuit Using 4047 IC

2010-02-26T18:56:00.000-08:00

This is a design circuit for the inverter circuit. This circuit is very simple diagram, at this circuit using CD4047 IC that functions to generate a wave 50Hz. This circuit uses 12V input (12V battery) to out 220V 50HZ. For safety please note for the installation of cooling on the components and 2N3055 transistors TIP122, it serves to remove excess heat transistor. This is the figure of the circuit.

6V Ultra-Bright LED Chaser Circuit

2010-01-24T08:31:00.000-08:00

This is a design circuit for lights Ultra-Bright LEDs in a sequence and each LED flashes brightly very briefly. The LEDs light-up going around and around since they are mounted in a circle (on a CD), then they pause before chasing again. The very brief flash of each LED (15ms) and the pauses (1 second) reduce the average current so the battery should last a long time. This is the figure of the circuit.

At maximum speed, the LEDs don’t appear to flash, instead they appear to move from one lighted one to the next, around and around. They rotate completely for 4 rotations in two seconds, and then turn off for a one second pause then repeat the sequence. At a lower speed, the number of rotations before the pause is less. It will do three rotations, two or even only one rotation at its slowest speed. A sequence of rotations starts with LED #2 and end with LED #9. The CD74HC4017N high-speed CMOS IC is rated for a maximum supply voltage of 7V. It is rated for a maximum continuous output current of 25mA. In this project, the maximum supply voltage is 6.4V with brand new battery cells and the 24mA output current is so brief that the IC runs cool. The MC14584BCP* IC (Motorola) is an ordinary “4XXX series” 3V to 18V CMOS IC, with a very low operating current and low output current. Its extremely high input resistance allows this project to use high value resistors for its timers and oscillators, for low supply current. Its 6 inverters are Schmitt triggers for simple oscillators and very quick switching.

Part:
Battery: Four AA alkaline cells.
Battery life:
Minimum speed and brightness 2.3 years
Medium speed and brightness 1 year
Minimum speed, maximum brightness 4.1 months
Maximum speed and brightness 3.8 weeks

Brightness: controlled with Pulse width Modulation, from off to extremely bright (4000mcd).
Stepper speed: 2 LEDs/sec to 2 revolutions/sec.
Pulse Width Modulation frequency: 3.9KHz.
LED current: 24mA pulses.
LED voltage drop: 3.2V at 24mA. Blue, green and white Ultra-Bright LEDs are suitable.
Minimum battery voltage:
<3v,>

Decibel Meter

2010-01-10T14:07:00.001-08:00

The circuit below responds to sound pressure levels from about 60 to 70 dB. The sound is picked up by an 8 ohm speaker, amplified by a transistor stage and one LM324 op-amp section. You can also use a dynamic microphone but I found the speaker was more sensitive. The remaining 3 sections of the LM324 quad op-amp are used as voltage comparators and drive 3 indicator LEDs or descents which are spaced about 3dB apart. This is the figrue of the circuit.

An additional transistor is needed for incandescent lights as shown with the lower lamp. I used 12 volt, 50mA lamps. Each light represents about a 3dB change in sound level so that when all 3 lights are on, the sound level is about 4 times greater than the level needed to light one lamp. The sensitivity can be adjusted with the 500K pot so that one lamp comes on with a reference sound level. The other two lamps will then indicate about a 2X and 4X increase in volume.

In operation, with no input, the DC voltage at pins 1,2 and 3 of the op-amp will be about 4 volts, and the voltage on the (+) inputs to the 3 comparators (pins 5,10,12) will be about a half volt less due to the 1N914 diode drop. The voltage on the (-) comparator inputs will be around 5.1 and 6.5 which is set by the 560 and 750 ohm resistors.

12 V – 120 V Inverter Circuit

2010-01-10T14:00:00.000-08:00

Ever needed a low power 120volt AC power source for your car, van or truck? Well this circuit should do the trick for you. This is the design for the problem. The circuit will supply 15 watts of AC power to a device. The circuit should power lamps, shavers, small stereos and small appliances. This is the figure of the circuit.

If you draw to much power the circuit will shut down all by itself. The output of this circuit is a square wave so there may be some noticeable hum on audio units plugged into it. To reduce some of the hum increase the value of the output capacitor which is at .47uf now. That transistor in the circuit are high power PNP transistors. Radio Shack part number 276-2025 are good ones to use or TIP32. The transformer is a 24 volt 2 amp center tapped secondary Radio Shack part number 273-1512 or equivalent.

Operational Amplifier Comparator Design

2009-12-30T14:21:00.001-08:00

This is a design for comparator circuit. In operation the operational amplifier goes into positive or negative saturation dependent upon the input voltages. This is the figure of the design circuit.

Although op amps are widely used as comparator, special comparator chips are often used. These integrated circuits offer very fast switching times, well above those offered by most op-amps that are intended for more linear applications. Typical slew rates are in the region of several thousand volts per microsecond, although more often figures of propagation delay are quoted. A typical comparator circuit will have one of the inputs held at a given voltage. This may often be a potential divider from a supply or reference source. The other input is taken to the point to be sensed.

Twang Matic Effect for Electric Guitar

2009-12-13T16:27:00.001-08:00

This circuit is design circuit that can be used to produce sound effects, but especially for guitar. This circuit is work with based on transistor. This is the figure of the circuit schematic.

The feature of this series is going to cut the signal and prevent low and pass only the signal with high frequency. Circuit diagram is very simple. Switch SW1 is a switch to bypass and SW2 to ON-OFF circuit. Resistor R7 which is a potentiometer used as volume control, to adjust the output level to get the signal level is best, i. e the signal with the smallest distortion.

Part:
R1, R5 = 1M
R2 = 10K
R3 = 20K
R4 = 18K
R6 = 4K7
R7 = 50K
C1 = 0.01 UF
C2 = 2uF/16V
C3 = 1uF
C4 = 0.05 UF
Q1, Q2 = 2N3302
BT1 = 9V

Octave Shift Effect for Electric Guitars

2009-12-13T16:26:00.001-08:00

This is design circuit for producing sound effects, this is an equipment used for electric guitar is highly sought. And one of the most widely used by rock guitarists of his full equipment is sliding octave. This circuit is based on LM741. Here’s the figure of the circuit.

By applying the method of the bridge diodes in the feedback path U2 LM741, it is not linear voltage characteristics of diode-diode it will not affect the incoming signal. Strengthening the beginning of the incoming guitar signal carried by the OP-amp U1 LM741. This strengthening in such a way set by the reset signal R1 so right on the cutting position. Then to reset the R4 can be arranged in such a way to level out the same signal with the incoming signal.

Switch SW1 which is a bypass, is a switch that serves what if the unit is not used. Signals are not only duplicated it, but also made so that the sound disabled and it is one of the most interesting because the effect will be produced with unique characteristics. Memeng with such a shift would voice sounded a bit harsh.

Part:
C1, C2 = 470nF
C3, C4, C5 = 100nF
D1 = BRIDGE
R1 = 25K
R2 = 2M7
R3 = 1K2
R4 = 100K
SW1 = SW MAG-SPDT
U1, U2 = LM741

Bass Effect Guitar Preamp Circuit

2009-12-13T16:23:00.000-08:00

This is the Bassman 5F6-A preamp contains two voltage amplifiers, one for the bright inputs and one for the normal inputs. The preamp is designed to boost the relatively weak signals from the guitar pickup and to suppress radio frequency interference. This is the figure of the circuit.

The boost comes from a medium-mu 12AY7 triode with a fully bypassed cathode. (In designs based on the 5F6-A this tube is often replaced by a high-mu 12AX7 triode.) The RF suppression results from 68k grid stoppers in combination with the Miller Capacitance of the tube. There are four inputs: fully amplified normal and bright channels (the #1 inputs) and attenuated normal and bright inputs (the #2 inputs). Except for the highest audio frequencies, where Miller Capacitance becomes a factor, the input impedance is 1 mega ohm at the #1 inputs and 136k at the #2 inputs. Based on a graphical analysis of the tube’s AC characteristics at the DC operating point, the 12AY7 amplification factor is estimated to be 49.1 and the plate resistance is equal to 29.9k. The voltage gains are thus -32.2 and -16.1, respectively, depending on which input is used. These are not the gains that are achieved when connected to the next stage, however, because the output impedance is significant: 23k.

100W Guitar Amplifier Circuit

2009-12-13T16:21:00.000-08:00

This is a circuit of the amplifier. This circuit is useful for electric guitar. This circuit is based on op amp TL072. This is the figure of the circuit.

The amp is rated at 100W into a 4 Ohms load, as this is typical of a "combo" type amp with two 8 Ohm speakers in parallel. For the really adventurous, 2 quad boxes and the amp head will provide 100W, but will be much louder than the twin. This is a common combination for guitarists, but it does make it hard for the sound guy to bring everything else up to the same level. This is a fully revised version of the original 100W guitar amp, and although there are a great many similarities, there are some substantial differences - so much so that a new version was warranted.

Medium Wave Active Antenna Circuit

2009-12-09T22:14:00.000-08:00

This is a design for amplify the input from a telescopic whip antenna. This circuit is based on MOSFET. Here’s the circuit diagram.

Operation of this circuit is begin when RV1 is the gain control allowing weak signals to be amplified or strong signals to be attenuated. The control voltage is applied to gate 2 of TR1, a dual-gate MOSFET, the signal voltage applied via gate 1; the input signal being double tuned via the 330uH coil and the two KV1235 varicap diodes at the MOSFET's input and by the same components at the BF981 MOSFET's drain terminal. Both tuned circuits provide high selectivity across the entire tuning range. To aid stability the MOSFET stage is fed from a 6.2V zener stabilized supply.

The preamplifier is designed to cover the medium waveband from about 550Khz to 1650Khz. The tuning voltage is supplied via RV2, a 10k potentiometer connected to the 12 Volt power supply.

Automatic Loudness Control Circuit

2009-12-09T22:10:00.000-08:00

This is project circuit for audio loudness control. This circuit is control using dual op amp. This is the figure of the project circuit.

A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels. Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7.

Part:
P1_________________10K Linear Potentiometer (Dual-gang for stereo)

R1,R6,R8__________100K 1/4W Resistors
R2_________________27K 1/4W Resistor
R3,R5_______________1K 1/4W Resistors
R4__________________1M 1/4W Resistor
R7_________________20K 1/2W Trimmer Cermet

C1________________100nF 63V Polyester Capacitor
C2_________________47nF 63V Polyester Capacitor
C3________________470nF 63V Polyester Capacitor
C4_________________15nF 63V Polyester Capacitor
C5,C9_______________1µF 63V Electrolytic or Polyester Capacitors
C6,C8______________47µF 63V Electrolytic Capacitors
C7________________100pF 63V Ceramic Capacitor

IC1_______________TL072 Dual BIFET Op-Amp

SW1________________DPDT Switch

Super Bridge 120W Power Amplifier Circuit

2009-12-08T23:00:00.000-08:00

This is a design for power amplifier. However, the amplifier is called Super Power Amp Bridge (BCL) 120W.

The main control circuit uses a BD249 transistor, IC TDA2030, TIP41, TIP31 or C1061 and BD250, TIP42, TIP32, A671. Here’s the schematic figure of the circuit.

13,8 V Power Supply Using LM338

2009-12-08T22:56:00.000-08:00

This is a design circuit for power supply. This circuit produces voltage 13,8 VDC. This circuit is work with based on LM338. Here’s the figure of the power supply circuit.

Maybe we need a supply of relatively strong in the framework we provide a variety of equipment with + 13.8V, as transceivers CB, and others known to use a complete circuit is capable of giving her the inside out, now constantly 5A and 12A peak current operations.

Part Components:
R1=270R 1/4W 2%
C1=10000uF 40V
C2-3=100 nF 100V Polyester
C4-5=10uF 25V
T1=220Vac/15VAC – 8A Mains Transformer
TR1=4k7 (Multiturn)
D1-2=1N4002 (1A/100V)
S1=2 Pole Single Throw Mains Switch
B1=25A Bridge Rectifier
F1=250mA Fuse
IC1=LM338

Source : users.otenet.gr/~ahisrod

Telephone Ring Generator Circuit

2009-12-06T13:46:00.001-08:00

This is circuit that produces a ring generator will ring a telephone once every 10 seconds. The interval between rings can be lengthened or shortened by varying the value of the 1 Mega Ohm of resistor. Here’s the circuit schematic.

This circuit is using small power transformer. The 70 volt/ 30 Hz ring voltage is produced from the 120 volt side of a small 12.6 VAC power transformer (Radio Shack 273-1365). Both capacitors connected across the transformer windings are non-polarized / 100 volts. Circuit draws about 300mA from the 12 volt DC power supply during the ringing interval. This circuit is controlled by 556 timer IC.

Oscillator Circuit Using Watch Crystal

2009-12-06T13:42:00.001-08:00

This is a design circuit for a couple circuits that can use to produce a 32.768 KHz square wave from a common watch crystal. This is a simple form design circuit. This is the figure of the circuit.

The output can be fed to a 15 stage binary counter to obtain a 1 second square wave. The circuit on the left using the 4069 inverter is recommended over the transistor circuit and produces a better waveform. The single transistor circuit produces more of a ramping waveform but the output swings the full supply voltage range so it will easily drive the input to a CMOS binary counter.

Long Time Delay Generator

2009-12-06T13:40:00.000-08:00

This circuit is design for produces a delaying time in several hours and it can be accomplished by using a low frequency oscillator and a binary counter. This circuit is controlled by CD4040 single chip IC. This is the figure of the circuit.

The frequency is divided by two at each successive stage of the 12 stage binary counter (CD4040) which yields about 1 hour of time before the final stage (Q12) switches to a high state. Longer or shorter times can be obtained by adjusting the oscillator frequency or using different RC values. Each successive stage changes state when the preceding stage switches to a low state (0 volts), thus the frequency at each stage is one half the frequency of the stage before. Waveform diagrams are shown for the last 3 stages. To begin the delay cycle, the counter can be reset to zero by momentarily connecting the reset line (pin 11) to the positive supply. Timing accuracy will not be as good as with a crystal oscillator and may only be around 1 or 2% depending on the stability of the oscillator capacitor.

Delayed Pulse Circuit

2009-12-06T13:35:00.001-08:00

This circuit is design for generating a single positive pulse which is delayed relative to the trigger input time. This circuit is based on 555 timer IC. This is the figure of the circuit.

When the button is depressed, the output of the first stage will move up and remain near the supply voltage until the delay time has elapsed, which in this case is about 1 second. The second 555 stage will not respond to the rising voltage since it requires a negative, falling voltage at pin 2, and so the second stage output remains low and the relay remains de-energized. At the end of the delay time, the output of the first stage returns to a low level, and the falling voltage causes the second stage to begin it's output cycle which is also about 1 second as shown. This same circuit can be built using the dual 555 timer which is a 556, however the pin numbers will be different.

2 Watt Amplifier Circuit

2009-12-06T13:33:00.000-08:00

This is a design circuit for amplifier. This circuit is produces 2 Watt amp and made using discrete components. This is the figure of the circuit.

The amplifier operates in Class AB mode; the single 470R preset resistor, PR1 controls the quiescent current flowing through the BD139/140 complimentary output transistors. Adjustment here, is a trade-off between low distortion and low quiescent current. Typically, under quiescent conditions, current is about 15 mA rising to 150 mA with a 50 mV input signal. The circuit is not perfect, this amplifier does have a wide frequency response, low harmonic distortion about 1.5%, and is capable of driving an 8 ohm speaker to output levels of around 5 watts with slightly higher distortion. The circuit is DC biased so that the emitters of the BD139 and BD140 are at approximately half supply voltage, to allow for a maximum output voltage swing.

APD Bias Supply Circuit

2009-12-02T22:36:00.000-08:00

This is design circuit for a high voltage APD bias supply. This circuit is design for current monitor function. This is the figure of the circuit.

This circuit is based on LT1930A switching regulator and L1 form a fly back based boost stage. The fly back events pump a diode-capacitor network tripler, producing a high voltage DC output. Feedback from the output via the R1-R2 combination stabilizes the regulator’s operating point D6 and D7 protect the switch and feedback pins, respectively, from parasitic negative excursions and the 10W resistors prevent excessive switch current. C8 and C9, series connected for high voltage capability, minimize output noise. A 0V to 4.5V programming voltage results in a corresponding 90V to 30V output (3% accuracy) with about 2mA of current capacity. Circuit output noise is quite low. Figure 7, taken with 500mA loading at VOUT = 50V, shows about 200mV ripple and harmonic residue in a 10MHz bandwidth. This is adequate for most APD receivers.

[Circuit’s source design: Linear Technology Notes].

Thermistor Stabilized Circuit

2009-12-01T11:05:00.001-08:00

This circuit is very similar to the lamp stabilized, but can be expected to have better distortion figures. This circuit is based on transistor. There is more amplitude bounce with the thermistor because it has a longer thermal time-constant, but this contributes to its lower distortion. This is the figure of the circuit.

As can be seen, it is very similar to the previous circuit, but the feedback impedance is higher. This will also help lower the circuit's distortion, but as I stated earlier, the thermistor is not easy to get.

Square Wave Generator Using CMOS 74C14 Single Integrated Circuit Chip

2009-12-01T11:04:00.000-08:00

Many ways to create a square wave output, but by far the simplest is to use a CMOS Hex Schmitt trigger inverter. These are fast, and with the outputs in parallel, will provide enough drive to ensure that the rise and fall times are very short indeed. This is one design circuit for the square wave generator. This is the figure.

This circuit is based on CMOS IC 74C14. The output of this circuit is from 0V to +12V, and is fed to the 10k level pot by a 10k resistor. This reduces the level to 6V P-P, which is equal to 3V RMS. The input circuit is designed to ensure that the Schmitt input is supplied from a 1/2 supply voltage (6V), so the applied AC will swing evenly about this point and produce a symmetrical square wave.

Avoiding Electrolysis for Water Level Detector Probes

2009-12-01T11:03:00.001-08:00

In the electrolysis process has been the primary cause of your water level detector probes, and you can avoid this by sensing the current by this probe using alternating current. This circuit is one design for the problems. This is the figure of the circuit.

This circuit is very simple. In alternating current, the electrolysis process will be reversed for every alternating cycles, making the probe will last longer to survive from corrosion. The whole circuit is consists of oscillator and detector. The oscillator is build around U1A. The capacitor C2 is inserted between the oscillator output and the probe to block DC signal, same as the C3 capacitor function. When the probe is submersed under water, an alternating current generated by the oscillator will flow through C2, probes, and C3. The alternating current from C3 is then rectified by D2 and filtered by C4 to get back the DC voltage. The diode D1 is provided to give the back flow path for the alternating current. Without D1, the alternating current won’t flow since the D2 diode only permit the current to flow for one direction. The DC level is detected on the C4 then triggering the U1B gate to turn on the relay. You can control a water pump using the relay output to turn on the pump if the water level is below the probes, and turn off when they’re submersed.

Temperature Controller Circuit

2009-11-30T01:14:00.000-08:00

This is the design circuit for control the temperature that is will temperature-control an oven at 75 degrees Celcius. This is the figure of the circuit.

This is ideal for most types of quartz crystals. 5V single supply operation allows the circuit to be powered directly from TTL-type rails. A1, operating at a gain of 100, determines the voltage difference between the temperature set point and the LM335 temperature sensor, which is located inside the oven. The temperature set point is established by the LM103-3.9 reference and the 1k-6.8k divider. A1's output biases C1, which functions as a pulse width modulator and biases Q1 to deliver switched mode power to the heater. When power is applied, A1's output goes high, causing C1's output to saturate low. Q1 comes on and delivers DC to the heater. When the oven warms to the set point, A1's output falls and C1 begins to pulse width modulate the heater in servo control fashion. In practice the LM335 should be in good thermal contact with the heater to prevent servo oscillation. [Schematic’s source: National Semiconductor Notes]

Servo Amplifier Using LM12

2009-11-30T01:12:00.000-08:00

When making servo systems with a power op amp, there is a temptation to use it for frequency shaping to stabilize the servo loop. This is a circuit for implementation the servo amplifier. This is the figure of the circuit.

This motor/tachometer servo gives an output speed proportional to input voltage. A low-level op amp is used for frequency shaping while the power op amp provides current drive to the motor. Current drive eliminates loop phase shift due to motor inductance and makes high-performance servos easier to stabilize. [Circuit’s source: National Semiconductor Notes].

Sample Hold Circuit Using Op Amp

2009-11-30T01:11:00.000-08:00

This is an implementation for sample hold circuit function that using op amp LM324. This is the figure of the circuit.

In this circuit, the input-to-output wiring has similar to standard configuration, but its operating principle is different. Key advantages include simplicity, no hold step, essentially zero gain error and operation from a single 5V supply. The sample-hold command pulse is applied to Q3, which turns on, causing current source transistor Q4's collector to go to ground potential. Amplifier A1 follows Q4's collector voltage and provides the circuit's output. When the sample-hold command pulse falls, Q4's collector drives a constant current into the 0.01 mF capacitor.

When the capacitor ramp voltage equals the circuit's input voltage, comparator C1 switches, causing Q2 to turn off the current source. At this point the collector voltage of Q4 sits at the circuit's input voltage. Q1 insures that the comparator will not self trigger if the input voltage increases during a ``hold'' interval. When a DC biased sine wave is applied to the circuit the sampled output is available at the circuit's output. The ramping action of the Q4 current source during the ``sample'' states is just visible in the output. [Schematic circuit source: National Semiconductor Notes].

Linear Platinum RTD Thermometer Circuit

2009-11-30T01:09:00.001-08:00

This is the design for a thermometer. This circuit is work with based on LM392. The IC is used to provide gain and linearization for a platinum RTD in a single supply thermometer circuit which measures from 0 degrees C to 500 degrees C with g 1 degrees C accuracy. This is the figure of the circuit.

Q1 functions as a current source which is slaved to the LM103-3.9 reference. The constant current driven platinum sensor yields a voltage drop which is proportionate to temperature. A1 amplifies this signal and provides the circuit output. Normally the slight nonlinear response of the RTD would limit accuracy to about g3 degrees. C1 compensates for this error by generating a breakpoint change in A1's gain for sensor outputs above 250 degrees C. When the sensor's output indicates 250§C, C1's ``a'' input exceeds the potential at the ``b'' input and C1's output goes high. [Circuit’s source: National Semiconductor Notes].

Fed Forward Low Pass Filter Circuit

2009-11-30T00:42:00.001-08:00

This is a circuit that useful for common filtering problems. This single supply circuit allows a signal to be rapidly acquired to final value but provides a long filtering constant. This characteristic is useful in multiplexed data acquisition systems and has been employed in electronic infant scales where fast, stable readings of infant weight are desired despite motion on the scale platform. This is the figure of the circuit.

How is the circuit work? When an input step is applied, C1's negative input will immediately rise to a voltage determined by the 1k pot-10 kX divider. C1's ``a'' input is biased through the 100 kX-0.01 mF time constant and phase lags the input. Under these conditions C1's output will go low, turning on Q1. This causes the capacitor to charge rapidly towards the input value. When the voltage across the capacitor equals the voltage at C1's positive input, C1's output will go high, turning off Q1. Now, the capacitor can only charge through the 100k value and the time constant will be long. Waveform B clearly shows this. The point at which the filter switches from short to long time constant is adjustable with the 1 kX potentiometer. Normally, this is adjusted so that switching occurs at 90%±98% of final value, but the photo was taken at a 70% trip point so circuit operation is easily discernible. A1 provides a buffered output. When the input returns to zero the 1N933 diode, a low forward drop type, provides rapid discharge for the capacitor. [Circuit’s source: National Semiconductor Notes].

Exponential Voltage - Frequency Converter for Electronic Music

2009-11-30T00:40:00.001-08:00

In an electronic music synthesizers require voltage controlled frequency generators whose output frequencies are exponentially related to the input voltages. This is one solution for the problem. This is a circuit for convert voltage to frequency. This is the figure of the circuit.

This circuit has performs this function with 0.25% exponential conformity over a range from 20 Hz to 15 kHz using a single LM392 and an LM3045 transistor array. The exponential function is generated by Q1, whose collector current will vary exponentially with its base-emitter voltage in accordance with the well known relationship between BE voltage and collector current in bipolar transistors. Normally, this transistor's operating point will vary wildly with temperature and elaborate and expensive compensation is required. In this circuit, Q1 is part of an LM3045 transistor array. Q2 and Q3, located in the array, serve as a heater sensor pair for A1, which servo controls the temperature of Q2. This causes the entire LM3045 array to be at constant temperature, eliminating thermal drift problems in Q1's operation. Q4 acts as a clamp, preventing servo lock-up during circuit start-up.

Adjustable Ratio Digital Divider Circuit

2009-11-30T00:34:00.000-08:00

This circuit is allows a digital pulse input to be divided by any number from 1 to 100 with control provided by a single knob. The function of this circuit is ideal for bench type work where the rapid set-up and flexibility of the division ratio is highly desirable. When the circuit input is low, Q1 and Q3 are off and Q2 is on. This is the figure of the circuit.

When the input goes high Q2 goes off and Q1 turns on Q3. This causes Q3 to displace the 100 pF capacitor's charge into A1's summing junction. A1's output responds by jumping to the required value to maintain the summing junction at 0V. This sequence is repeated for every input pulse. During this time A1's output will form the staircase shape. When A1's output is great enough to just bias C1's ``a'' input below ground, C1's output goes low and resets A1 to 0V. [Circuit’s source: National Semiconductor Notes].

The Basic of Op Amp

2009-11-24T19:44:00.001-08:00

The op-amp is basically a differential amplifier having a large voltage gain, very high input impedance and low output impedance. The op-amp has a "inverting" or (-) input and "non-inverting" or (+) input and a single output. This is a form of op amp.

The inverting op-amp is connected using two resistors RA and RB such that the input signal is applied in series with RA and the output is connected back to the inverting input through RB. The non-inverting input is connected to the ground reference or the center tap of the dual polarity power supply. In operation, as the input signal moves positive, the output will move negative and visa versa. The amount of voltage change at the output relative to the input depends on the ratio of the two resistors RA and RB. As the input moves in one direction, the output will move in the opposite direction, so that the voltage at the inverting input remains constant or zero volts in this case.

The non-inverting amplifier is connected so that the input signal goes directly to the non-inverting input (+) and the input resistor RA is grounded. In this configuration, the input impedance as seen by the signal is much greater since the input will be following the applied signal and not held constant by the feedback current. As the signal moves in either direction, the output will follow in phase to maintain the inverting input at the same voltage as the input (+). The voltage gain is always more than 1 and can be worked out from Vgain = (1+ RB/RA).

Simple Inverter Circuit for Florescent Lamps

2009-11-24T19:40:00.001-08:00

This circuit is very easy to construct, reliable, and even powerful enough to light up a 15W florescent tube. This circuit is constructs from transistor NPN and some components. This is the figure of the circuit.

This is a single transistor oscillator circuit. Current passed through primary winding inducts a magnetic field to the core and the core gives the energy back to the feedback winding with a delay determined by the core material and windings. System then oscillates continuously on a frequency depending on this timing. You cannot use 2SD882 with voltages over 4.5 volts. It is only needed if you are going to feed the circuit with only 4.5 volts.

Simple 1,3 Volt Power Supply Circuit

2009-11-24T19:38:00.001-08:00

This is the design for a replacement power source for 1.3V mercury cells or other small batteries. This circuit is useful for computer to power a front panel multi adapter which has a digital thermometer. This circuit is a simplest form of the schematic. This is the figure of the circuit.

This circuit takes it power from a PC. The power connectors have color coded wirings, red and black are a 12V supply, black and yellow are a 5V supply. These are extremely high current so absolute care must be taken to avoid short circuits and an inline fuse of 100mA is recommended. The 1.3V is derived from a Red LED. When on and forward biased the LED's voltage drop between anode and cathode is about 1.9V, this is too high for mercury cell powered equipment, but fed in series with a 1N4148 signal diode drops around 0.6V, the supply is then ideal to drive battery powered peripherals. This is not suitable for clocks, because when the computer is turned off the 5V supply is also switched off. It is however ideal for the independent temperature displays often included with PC peripherals such as case mounted usb connectors.

Notch Filter Circuit

2009-11-24T19:36:00.000-08:00

This is a design for a filter. This circuit is called as variable notch filter with both high and low pass filters. This is the figure of the circuit.

This circuit is based on LF351 for sensing the filter processing. At first glance this circuit looks fairly complex, but when broken down, it can be divided into high pass and low pass filter sections followed by a summing amplifier with a gain of around 20 times. Supply rail voltage is +/- 9V DC. The controls may also be adjusted for use as a band stop (notch) filter or band pass filter.

High Voltage Regulator Power Supply

2009-11-24T19:35:00.001-08:00

This is a design circuit for a power supply. This circuit is basic for high power supply that is based on LM317 for the regulator IC. This is the figure of the circuit.

How is the circuit work? Zener diode D1 ensures that the LM317H sees only a 5V input-output differential over the entire range of output voltage from 1.2V to 160V. Since high-voltage transistors by necessity have a low β, a Darlington is used to stand off the high voltage. The zener impedance is low enough that no bypass capacitor is required directly at the LM317 input. (In fact, no capacitor should be used here if the circuit is to survive an output short!) R3 limits short circuit current to 50 mA. The RC network on the output improves transient response as does by passing the ADJUST pin, while R4 and D2 protect the ADJUST pin during shorts. [Circuit schematic source: National Semiconductor Notes].

50V 3A Stabilized Power Supply

2009-11-24T19:32:00.000-08:00

This is a design for power supply. This is a complete circuit for the stabilized power supply. This is the figure of the circuit.

This circuit can give in his exit + 40V until + 60V 3A, with simultaneous stabilization. The materials that use is very simple and will not exist difficulties in the manufacture, is enough you are careful certain points. For output voltages smaller of + 50V until + 40V, the Q1 is hot enough, so that it needs one big heat sink. This circuit is work using transistor 2N3055.

Broadband Random Noise Generator Circuit

2009-11-10T17:36:00.001-08:00

This circuit is often needed in testing any type of electronic systems such as filter, audio, or RF communication. The circuit presented here generates an RMS amplitude regulated noise source with selectable bandwidth. This circuit is work based on op amp. This is the figure of the circuit.

With 1 KHz to 5 MHz decade ranges selectable bandwidth and 300mV RMS output, this noise generator is suitable for wide range of application. Noise is generated by D1 that is AC coupled to A2, an amplifier with broadband gain 100. The output of A2 is fed to a simple selectable low-pass filter. The filter’s output is applied to LT1228 operational trans-conductance amplifier A3. A3’s output feeds current feedback amplifier LT1228 A4. A4’s output, which is also the circuit’s output, is sampled by the A5-based gain control configuration. This closes a gain control loop to A3. A3’s ISET current controls gain, allowing overall output level control.

Audio Mixer Using FET

2009-11-10T17:35:00.001-08:00

This is a simple project circuit for mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consume very little power. This is the figure of the circuit.

This circuit is based on or built by FET 2N3819. The circuit can be powered by a single 9 volt battery. As many or as few channels as are required can be added to the mixer. A shielded case is probably needed to reduce hum and help stop oscillations.

Part:
R1, R3 10K Pot
R2, R4 100K 1/4 W Resistor
R5 6.8K 1/4 W Resistor
C1, C2, C3 0.1uF Capacitor
Q1 2N3819 Junction FET
MISC Wire, Shielded (Metal) Case, Phone or Other Plug For Output

Open Loop Fast Peak Detector Circuit Using Op Amp

2009-11-06T09:37:00.001-08:00

This is a design for peak detector. This circuit is a fast peak detector similar but faster than previous peak detector, can be implemented using open loop configuration. This circuit is based on op amp LT1190. This is the figure of the circuit.

In this design, D1 is the detector diode and D2 is a level shifting or compensating diode. A load resistor RL is connected to – 5V and an identical bias resistor, RB, is used to bias the compensating diode. This equal value resistor is RL and RB makes sure that the diode drops are equal. Low values of RB and RL (1k to 10k) yield in fast response, at the expense of poor low frequency accuracy. High values of RB and RL provide good low frequency accuracy but cause the amplifier to slew rate limit, resulting in poor high frequency accuracy. A solution can be made by adding a feedback capacitor CFB, which improve the negative slew rate on the (–) input. We can expect under 15% amplitude error for 2Vpp-6Vpp input at 20MHz, much faster than closed loop design. [Circuit source: Linear Technologies, Inc].

Stepper Motor Controller Circuit

2009-11-06T09:30:00.000-08:00

This is a circuit for motor stepper controller. A stepper motor controller is needed to run a stepper motor, since a stepper motor cannot work by just connecting it to a power supply. To program a stepper motor to make a complex movement, we usually need a micro controller. This is the figure of the circuit.

This stepper motor controller circuit is still need an external input. If we look at the table, the input pattern is similar to a 2 bits binary counter. If you have an up-down binary counter, then you get a forward-reverse control for your stepper motor. This circuit is very simple design.

Phase Control

2009-11-06T09:26:00.000-08:00

This is a phase control circuit that can be used to control the power delivered to an AC load. The phase control circuit is to control the AC waveform, cutting the cycle to give full cycle, half cycle, zero cycle, or somewhere in between. This circuit is similar to a dimmer circuit, but the switching is synchronized with the zero crossing of the waveform. This is the figure of the circuit.

The benefit of switching the power in zero crossing condition is that the triacs doesn’t suffer power dissipation, thus increasing the overall efficiency. This phase control circuit is suitable for brushed AC motor, heater filament, or incandescent lamps. The integrated circuit, U208B, is designed as a phase control circuit in bipolar technology with internal supply-voltage monitoring. As the voltage is built up, uncontrolled output pulses are avoided by internal monitoring. Furthermore, it has internal-current and voltage synchronization. It is recommended as a low cost open-loop control.

Audio Frequency Meter Using 555 Timer IC

2009-10-20T22:50:00.001-07:00

This is a circui for audio frequency meter. This circuit uses 555 IC as a mono stable multi vibrator (one-shoot trigger). A mono stable multi vibrator can act as a frequency-to-voltage converter because it produces a fixed pulse width, with the repetition rate/density is proportional to the triggering input frequency. This is the figure of the circuit.

For resistor R1, because it set the measurement range, it’s better to use a rotary switch to select different values for different ranges. For the ampere meter, you can use analog or digital ampere meter. A cheap dual-slope ADC digital meter is suitable because its averaging characteristic, but a fast digital multimeter can also be used although it may show some uncertainty because of their fast sampling.

Simple 8 Watt Audio Power Amplifier

2009-10-20T22:49:00.001-07:00

This is an audio power amplifier circuit using only a single chip and few passive components, that you can build 8-14 Watt audio power amplifier using TDA2030 chip. This is very simple circuit. This is the figure of the circuit.

When you use 4 ohm speaker then you get 14 Watt output power, and around 8 Watt if you use 8 ohm loudspeaker. Make sure the 100n and 100u capacitor is wired as close as possible to the power input pin of the TDA 2030. You might wonder why we use 100uF and 100nf in parallel, if you think that we need 100.1uF capacitor then you’re wrong. All we need is just a capacitor around 100uF with small equivalent series inductance. At low frequency, the “relatively high” series inductance of the 100uF electrolytic capacitor can be neglected, but not for the high frequency. At high frequency, the TDA2030 is protected from instability by the 100nF capacitor, because the signals find the low inductance path here to bypass the fast power source variation.