Monday, September 30, 2013

Servo Tester Using A 4538

There are times when a small servo tester for modeling comes in very useful. Everybody who regularly works with servos will know several instances when such a servo tester will come in handy. The function of a servo tester is to generate a pulsing signal where the width of the positive pulse can be varied between 1 and 2 ms. This pulse-width determines the position the servo should move to. The signal has to repeat itself continuously, with a frequency of about 40 to 60 Hz. These circuits often use an NE555 or one of its derivatives to generate the pulses. This time we have used a 4538 for variety. This IC contains two astable multi-vibrators. You can see from the circuit diagram that not many other components are required besides the 4538. The astable multi-vibrator in a 4538 can be started in two ways. When input I 0 (pin 5 or 11) is high, a rising edge on input I 1 (pin 4 or 12) is the start signal to generate a pulse.

Servo Tester using a 4538 circuit schematic

The pulse-width at the output of IC1a is equal to (R1+P1)×C1. This means that when potentiometer P1 is turned to its minimum resistance, the pulse-width will be 10 k × 100 n = 1 ms. When P1 is set to maximum (10 k), the pulse-width becomes 20 k × 100 n = 2 ms. At the end of this pulse inverting output Q generates a rising edge. This edge triggers IC1.B, which then generates a pulse. The pulse-width here is 82 k × 220 n ˜ 18 ms. At the end of this pulse the Q output will also generate a rising edge. This in turn makes IC1.A generate a pulse again. This completes the circle. Depending on P1, the total period is between 19 and 20 ms. This corresponds to a frequency of about 50 to 53 Hz and is therefore well within the permitted frequency range.
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Sunday, September 29, 2013

Low Battery Indicator II

This circuit indicates the remaining battery life bAy varying the duty cycle and flash rate of an LED as the battery voltage decreases. In fact, the circuit actually indicates five battery conditions: (1) a steady glow assures indicates that the battery is healthy; (2) a 2Hz flicker (briefly off) indicates that the battery is starting to show age; (3) a 5Hz 50% duty-cycle flash is a warning that you should have a spare battery on hand; (4) a brief flicker on at a 2Hz rate indicates the batterys last gasp; and (5) when the LED is continuously off, its time to replace the battery. IC1 is wired as an oscillator/comparator, with a nominal fixed voltage reference of about 1.5V on its pin 2 (inverting) input (actually, it varies between about 1.7V and 1.4V depending on the hysteresis provided via R6).

Low battery indicator circuit schematic

This reference voltage is derived from a voltage divider consisting of resistors R4 & R5, which are connected across the 5V rail derived from regulator REG1, and feedback resistor R6. Similarly, IC1s pin 3 input (non-inverting) is connected to a voltage divider consisting of R1 & R2 which are across the 9V battery. Using the component values shown, the circuit will switch LED1 from being continuously on to flash mode when the 9V battery drops to about 6.5V. Subsequently, LED1 is continuously off for battery voltages below 5.5V.

Naturally, you can tweak the resistor values in the divider network for different voltage thresholds as desired. In operation, the circuit oscillates only when the sampled battery voltage (ie, the voltage on pin 3) is between the upper and lower voltage thresholds set on pin 2. Capacitor C3 provides the timing. Above and below these limits, IC1 simply functions as a comparator and holds LED1 continuously on or off. Finally, to precisely set the "dead-battery" threshold, make R4 adjustable to offset the variations in regulator tolerance.
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Saturday, September 28, 2013

Push Bike Light

Automatic switch-on when it gets dark, 6V or 3V battery operation

This design was primarily intended to allow automatic switch-on of push-bike lights when it gets dark. Obviously, it can be used for any other purpose involving one or more lamps to be switched on and off depending of light intensity. Power can be supplied by any type of battery suitable to be fitted in your bike and having a voltage in the 3 to 6 Volts range.

The Photo resistor R1 should be fitted into the box containing the complete circuit, but a hole should be made in a convenient side of the box to allow the light hitting the sensor. Trim R2 until the desired switching threshold is reached. The setup will require some experimenting, but it should not be difficult.

Circuit diagram:

Push-Bike Light Circuit Diagram

Push-Bike Light Circuit Diagram


R1_____________Photo resistor (any type)
R2______________22K 1/2W Trimmer Cermet or Carbon type
R3_______________1K 1/4W Resistor
R4_______________2K7 1/4W Resistor
R5_____________330R 1/4W Resistor (See Notes)
R6_______________1R5 1W Resistor (See Notes)
D1____________1N4148 75V 150mA Diode
Q1_____________BC547 45V 200mA NPN Transistor
Q2_____________BD438 45V 4A PNP Transistor
LP1____________Filament Lamp(s) (See Notes)
SW1_____________SPST Toggle or Slider Switch
B1______________6V or 3V Battery (See Notes)


  • In this circuit, the maximum current and voltage delivered to the lamp(s) are limited mainly by R6 (that cant be omitted if a clean and reliable switching is expected). Therefore, the Ohms Law must be used to calculate the best voltage and current values of the bulbs.
  • For example: at 6V supply, one or more 6V bulbs having a total current drawing of 500mA can be used, but for a total current drawing of 1A, 4.5V bulbs must be chosen, as the voltage drop across R6 will become 1.5V. In this case, R6 should be a 2W type.
  • At 3V supply, R6 value can be lowered to 1 or 0.5 Ohm and the operating voltage of the bulbs should be chosen accordingly, by applying the Ohms Law.
  • Example: Supply voltage = 3V, R6 = 1R, total current drawing 600mA. Choose 2.2V bulbs as the voltage drop caused by R6 will be 0.6V.
  • At 3V supply, R5 value must be changed to 100R.
  • Stand-by current is less than 500µA, provided R2 value after trimming is set at about 5K or higher: therefore, the power switch SW1 can be omitted. If R2 value is set below 5K the stand-by current will increase substantially.

Source :

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Friday, September 27, 2013

Anti Theft Security For Car Audios

This small circuit, based on popular CMOS NAND chip CD4093, can be effectively used for protecting your expensive car audio system against theft. When 12V DC from the car battery is applied to the gadget (as indicated by LED1) through switch S1, the circuit goes into standby mode. LED inside optocoupler IC1 is lit as its cathode terminal is grounded via the car audio (amplifier) body. As a result, the output at pin 3 of gate N1 goes low and disables the rest of the circuit. Whenever an attempt is made to remove the car audio from its mounting by cutting its connecting wires, the optocoupler immediately turns off, as its LED cathode terminal is hanging. As a result, the oscillator circuit built around gates N2 and N3 is enabled and it controls the ‘on’/‘off’ timings of the relay via transistor T2. (Relay contacts can be used to energise an emergency beeper, indicator, car horns, etc, as desired.)

Circuit Diagrams

Anti-Theft Security For Car Audios

Different values of capacitor C2 give different ‘on’/‘off’ timings for relay RL1 to be ‘on’/‘off’. With 100µF we get approximately 5 seconds as ‘on’ and 5 seconds as ‘off’ time. Gate N4, with its associated components, forms a self-testing circuit. Normally, both of its inputs are in ‘high’ state. However, when one switches off the ignition key, the supply to the car audio is also disconnected. Thus the output of gate N4 jumps to a ‘high’ state and it provides a differentiated short pulse to forward bias transistor T1 for a short duration. (The combination of capacitor C1 and resistor R5 acts as the differentiating circuit.)As a result, buzzer in the collector terminal of T1 beeps for a short duration to announce that to announce that the security circuit is intact. This ‘on’ period of buzzer can be varied by changing the values of capacitor C1 and/or resistor R5. After construction, fix the LED and buzzer in dashboard as per your requirement and hide switch S1 in a suitable location. Then connect lead A to the body of car stereo (not to the body of vehicle) and lead B to its positive lead terminal. Take power supply for the circuit from the car battery directly.


  • This design is meant for car audios with negative ground only.

Author:T.K  Hareendran Copyright: Circuit Ideas

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Thursday, September 26, 2013

General Purpose Oscillator

The oscillator shown in Figure1 is frequently used in digital circuits and may, therefore, look very familiar. Many readers may not know that this type of oscillator suffers from a nasty draw-back caused by noise. When the amplitude of the noise is higher than the hysteresis of the gates used for the oscillator, spurious switching pulses are generated near the zero crossings. This problem can be cured only by ensuring that the rise time of the input signal is shorter than the reaction time of the relevant gate. When the oscillator is built with fast logic gates, such as those in the HC-series, the like-lihood of the problem occurring is great.

General Purpose OscillatorHowever, as long as the positive feedback is fast enough, nothing untoward will happen. However, when delays occur owing to the transit time of the components used, the problem may rear its head. In the configuration of Figure 1a, the signal passes through two inverters and thus experiences twice the transit time of a single gate. The upper signal in the oscilloscope trace in Figure 2 shows the result of this: the gates used are simply too fast for this type of oscillator. If one of the inverters is replaced by a buffer, and the oscillator is modified as shown in Figure 1b, the transit time is limited to that of one gate: the lower trace in Figure 2 shows that the oscillator then works correctly. The practical circuit diagram of the general-purpose oscillator is shown in Figure 3. Note that two XOR gates are used to ensure that the transit time of the buffer is equal to that of the inverter.

General Purpose Oscillator
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Wednesday, September 25, 2013

LED Flasher With One Transistor

The circuit uses a flashing LED to flash a super-bright 20,000mcd white LED

This is a novel flasher circuit using a sin istor that takes its flashrate from a flashing LED. The flasher in the photo is 3mm. An ordinary LED will not work.



The flash rate cannot be altered by the brightness of the high-bright white LED can be adjusted by altering the 1k resistor across the 100u electrolytic to 4k7 or 10k. The 1k resistor discharges the 100u so that when the transistor turns on, the charging current into the 100u illuminates the white LED.If a 10k discharge resistor is used, the 100u is not fully discharged and the LED does not flash as bright.

Circuit diagram:

LED Flasher Circuit diagram LED Flasher With One Transistor circuit diagram

All the parts in the photo are in the same places as in the circuit diagram to make it easy to see how the parts are connected.

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Tuesday, September 24, 2013

Case Modding

The aesthetics of ‘case modding’ (modifying a PC’s enclosure) offer plenty of scope for debate and plenty of scope for original circuits. Low current LED indicators are usually fitted in PC enclosures. Although this certainly saves energy, the LEDs do not light particularly brightly. It is not completely straightforward to replace the low-current types with high-brightness types since the latter draw a current of 20 mA rather than 2 mA. This can - whatever people might tell you to the contrary - in some instances lead to excessive load on the LED drivers on the motherboard.


The problem can be solved using a small external driver stage: two resistors and a transistor mounted on a small piece of perforated board, connected in place of the original LED. The new high-brightness LED is then connected between the output of the current source and a spare motherboard ground connection (for example on the infrared port) or to a grounded screw in the enclosure. R1 is responsible for the constant current. High-brightness red LEDs are driven at 20 mA (R1 = 150 Ω), whereas high-brightness blue LEDs require 10 mA (R1 = 75 Ω). In view of the large number of different PC motherboards available, it is not certain that this driver can be used in every PC. It is easy to check whether the circuit will work: use a DC voltmeter to measure the voltage between the positive connection on the LED (generally a red wire or a pin marked with an arrow on the LED connector) and ground (not the other pin of the connector). If this reads +5 V independent of whether the LED is on or not, then the driver can be used.

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Monday, September 23, 2013

Whistling Kettle

Most electric kettles do not produce a whistle and just switch off when they have boiled. Fitting a box of electronics directly onto an electric kettle (or even inside!) to detect when the kettle has boiled is obviously out of the question. The circuit shown here detects when the kettle switches off, which virtually all kettles do when the water has boiled. In this way, the electronics can be housed in a separate box so that no modification is required to the kettle. The box is preferably a type incorporating a mains plug and socket. In this application, the current flowing in coil L1 provides a magnetic field that actuates reed switch S1. Since the current drawn by the kettle element is relatively large (typically 6 to 8 amps), the coil may consist of a few turns of wire around the reed switch.

The reed switch is so fast it will actually follow the AC current flow through L1 and produce a 100-Hz buzz. The switching circuit driven by the reed switch must, therefore, disregard these short periods when the contacts open, and respond only when they remain open for a relatively long period when the kettle has switched off. The circuit is based on a simple voltage controlled oscillator formed around T2 and T3. Its operation is best understood by considering the circuit with junction R4/R5 at 0 V and C4 discharged. T2 will receive base current through R5 and turn on, causing T3 to turn on as well. The falling collector voltage of T3 is transmitted to the base of T2 by C4 causing this transistor to conduct harder.

Since the action is regenerative, both transistors will turn on quickly and conduct heavily. C4 will therefore charge quickly through T2’s base-emitter junction and T3. Once the voltage across C4 exceeds about 8.5 V (leaving less than 0.5 V across T2’s b-e junction), T2 will begin to turn off. This action is also regenerative so that soon both transistors are switched off and the collector voltage of T3 rises rapidly to +9 V. With C4 still charged to 8.5 V, the base of T2 will rise to about 17.5 V holding T2 (and thus T3) off. C4 will now discharge relatively slowly via R5 until T2 again begins to conduct whereupon the cycle will repeat. The voltage at the collector of T3 will therefore be a series of short negative going pulses whose basic frequency will depend on the value of C4 and R5.

The pulses will be reproduced in the piezo sounder as a tone. The oscillation frequency of the regenerative circuit is heavily dependent on the voltage at junction R4/R5. As this voltage increases, the frequency will fall until a point is reached when the oscillation stops altogether. With this in mind, the operation of the circuit around T1 can be considered. In the standby condition, when the kettle is off, S1 will be open so that C1 and C2 will be discharged and T1 will remain off so that the circuit will draw no current. When the kettle is switched on, S1 is closed, causing C1 and C2 to be discharged and T1 will remain off. C3 will remain discharged so that T2 and T3 will be off and only a small current will be drawn by R1.

Although S1 will open periodically (at 100 Hz), the time constant of R1/C1 is such that C1 will have essentially no voltage on it as the S1 contacts continue to close. When the kettle switches off, S1 will be permanently open and C1/C2 will begin to charge via R1, causing T1 to switch on. C3 will then begin to charge via R4 and the falling voltage at junction R4/R5 will cause T2/T3 to start oscillating with a rising frequency. However, once T1 has switched off, C3 will no longer be charged via R4 and will begin to discharge via R3 and R5 causing the voltage at R4/R5 to rise again. The result is a falling frequency until the oscillator switches off, returning the circuit to its original condition.

As well as reducing the current drawn by the circuit to zero, this mimics the action of a conventional whistling kettle, where the frequency rises as more steam is produced and then falls when it is taken off the boil. The circuit is powered directly by the mains using a ‘lossless’ capacitive mains dropper, C6, and zener a diode, D2, to provide a nominal 8 V dc supply for the circuit. A 1-inch reed switch used in the prototype required about 9 turns of wire to operate with a 2-kW kettle element. Larger switches or lower current may require more turns. In general, the more turns you can fit on the reed switch, the better, but do remember that the wire has to be thick enough to carry the current. It is strongly recommended to test the circuit using a 9-volt battery instead of the mains-derived supply voltage shown in the circuit diagram. A magnet may be used to operate S1 and so simulate the switching of the kettle.

This circuit is connected directly to the 230-V mains and none of the components must be touched when the circuit is in use. The circuit must be housed in an approved ABS case and carry the earth connection to the load as indicated. Connections and solder joints to components with a voltage greater than 200 volts across them (ac or dc) must have an insulating clearance of least 6 mm. An X2 class capacitor must be used in position C6.
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Sunday, September 22, 2013

US Style Siren

The circuit described here can create three different ‘US-style’ siren sounds: police, ambulance and fire engine. The desired sound can be selected using switch S1. The circuit can be used in toys (such as model vehicles), as part of an alarm system, and in many other applications. For use in a toy, a BC337 is an adequate device for driver T5, since it is capable of directly driving a 200mW (8Ω) loudspeaker. In this case the current consumption from a 9 V power supply is around 140 mA. If a louder sound is required, a BD136 is recommended: this can drive a 5W (8Ω) loudspeaker.
US-Style Siren Circuit DiagramThe current consumption from a 12 V supply will then be about 180mA. If still more volume is desired, then T5 (a BD136) can be used as a first driver stage, and a 15W (8Ω) loudspeaker can be connected via output transistor T6. Here an AD162 or an MJ2955 can be used, which, for continuous operation, must be provided with cooling. The peak current consumption of the circuit will now be about 500mA with a 12V power supply. Capacitor C1 is not required for battery operation.
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Saturday, September 21, 2013

1983 Ford Thunderbird Wiring Diagram

1983 Ford Thunderbird Wiring Diagram

The Part of 1983 Ford Thunderbird Wiring Diagram :windshield, wiper, motor, windshield washer pump, fuse block, stop light switch, backup light switch, neutral safety switch, blower motor, oil press switch, condenser, breaker, temp.gauge(eng.unit), distributor, cyl, breaker, condenser, distributor, cyl, coil, starter, alternator, yellow, brown, starter relay, black-yellow, alternator regulator, horn, parking light, direction signal, high beam, battery, low beam, low beam, high beam, direction signal, parking light.

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Friday, September 20, 2013

1995 Lincoln Town Car v 8 Wiring Diagram

1995 Lincoln Town Car v-8  Wiring Diagram

The Part of 1995 Lincoln Town Car v-8  Wiring Diagram : glove box lamp switch, glove box, left vanity mirror lamp, switch, grounds, solid state, garage door, engine compartment lamp, hodd, trunk lid lamp switch, trunk lid, front dome switch, lamp, rear dome switch, lamp.
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Wednesday, September 11, 2013

Build a Precision full wave Rectifier Circuit Diagram

This Precision full wave Rectifier Circuit Diagram  provides accurate full wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy current, except a small amount through the 10K resistors. Therefore, the load applied should be referenced to ground or a negative voltage. Reversal of all diode polarities will reverse the polarity of the output

Since the outputs of the amplifiers must slew through two diode drops when the input polarity changes, 741 type devices give 5% distortion at about 300 Hz.

Precision full wave Rectifier Circuit Diagram

Build a Precision full wave Rectifier Circuit Diagram
 Sourced By:
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Tuesday, September 10, 2013

Arduino Based Low Power Wireless Solution

panStamp is an open source project created for the enthusiasts that love measuring and controlling things wirelessly. panStamps are small wireless boards specially designed to fit in low-power applications, simple to program and simple to work with. With panStamps, you can measure almost everything by simply connecting your panStamp to the sensors, placing a battery and sending wireless data from the first moment.

Arduino Based Low-Power Wireless Solution

panStamps are suitable for any kind of project needing remote control and low-power wireless transmissions, including home automation, energy metering, weather monitoring and robot control. If you are one of these three things: a hobbyist, a professional or an end-user, you will find that panStamps provide extreme flexibility and power when creating custom wireless networks.
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Wednesday, September 4, 2013

Binary Coded Decimal BCD Clock

The clock circuit above uses seven ICs and 19 LEDs to indicate binary coded decimal time. The LEDs can be arranged (as shown in example above) so that each horizontal group of 3 or 4 LEDs represents a decimal digit between 0 and 9 and each individual LED represents a single bit or (binary digit) of the value. Binary digits have only two values (0 and 1) so a number written in binary would be something like 1001 or 0011, which represents decimal numbers 9 and 3 respectively. From right to left, each binary (1) represents increasing powers of 2, so that a 1 in the right hand place represents 2^0=1 and the next place to the left is 2^1=2 and then 2^2=4, and so forth.

This makes binary counting fairly easy since each digit has a value of twice the one before or 1,2,4,8,16,32,64,etc. Thus the decimal value can be found by simply adding the values of each illuminated LED in the same row, (the total is shown in the box to the right). For example, the binary number 1001 would have a decimal value of 8+0+0+1 = 9. But this is actually a binary coded decimal 9 since only values from 0 to 9 are used 0000 to 1001. A true binary clock indicating minutes of the hour would display values from 0 to 59, or 000000 to 111011. But this would be more difficult to read since adding values 32 + 16 + 8 + 2 + 1 = 59 is not as easy as 8 + 0 + 0 + 1 = 9.

Binary Coded Decimal (BCD) Clock Circuit diagram

Binary Coded Decimal (BCD) Clock
The circuit is powered by a small 12.6 VAC transformer which also provides a low voltage 60 Hz signal for a very accurate time base. The transformer is connected with the secondary center tap at ground which produces about 8 volts DC across the 3300uF filter capacitor. DC power for the circuit is regulated at about 5.5 using a NPN transistor (2N3053) and 6.2 volt zener diode. The 2N3053 gets a little warm when several LEDs are on, and may require a little (top hat type) heat sink.

A one second clock pulse is obtained by counting 60 cycles of the AC line signal. This is accomplished using a CMOS CD4040 12 stage binary counter (shown in light blue). The 60th count is detected by the two NAND gates connected to pins 2,3,5,and 6 of the counter. When all four of these lines are high, the count will be 60 resulting in a high level at pin 4 of the 74HC14 which resets the counter to zero and advances the seconds counter (74HC390 shown in purple) when pin 4 returns to a low state.

The same process is used to detect 60 seconds and 60 minutes to reset the counters and advance the minutes and hours counters respectively. In both of these cases the 2 and 4 bit lines of the tens counter section will be high (20+40=60). In all three cases (seconds, minutes and hours) a combination 10K resistor and 0.1uF capacitor is used at the input to the 74HC14 inverter to extend the pulse width to about 300uS so the counters will reliably reset. Without the RC parts, the reset pulse may not be long enough to reset all stages of the counter since as soon as the first bit resets, the inputs to the NAND gate will no longer all be high and the reset pulse will end. Adding the RC parts eliminates that possibility.

The reset process for the hours is a little different since for a 12 hour clock we need to reset the hours counter on the 13th count and then advance the counter one count so the display will indicate one ("1"). The 74HC00 quad NAND gate only has 4 sections with two inputs each so I used 3 diodes to detect the 13th hour (10 +1 +2 =13) which drives an inverter and also a transistor inverter (2N3904 or similar). The last 74HC14 inverter stage (pin 12 and 13) supplies a falling edge to the hours counter which advances the hours to "1" a short time after the reset pulse from the transistor inverter ends.

The pulse width from pin 12 of the inverter is a little shorter than from pin 10 which ensures that the hours clock line (pin 1 of yellow box) will move high before the end of the reset pulse form pin 10. If it were the other way around, the reset pulse may end before pin 12 of the inverter had a chance to reach a high level which would prevent the counter from advancing to "1". So it is important to use a shorter RC time at pin 13 than for the other Schmitt Trigger inputs. I used a 10K resistor and a 0.01uF cap to obtain the shorter time, but other values will work just as well. Only 2 sections of the 4071 OR gate are used, so the remaining 4 inputs (pins 8,9,12,13) should be terminated to ground if not used.

Copied Files Notice: This circuit diagram and text description has been copied and reposted without permission at: The copied file has also been altered to remove the authors name and date of creation which is a clear violation of copyright law. They have also copied and modified three Java Script Calculators from this website. I have e-mailed a request to have the calculators removed and received no answer. I have also contacted the web host at and received an autoresponse that the matter will be investigated but I doubt any action will occur. Please feel free to e-mail your opinions of plagiarism to

Parts List:
3 - 74HC390 - Dual BCD counters
1 - CD4040 - 12 Stage Binary Counter
1 - 74HC14 - Hex Schmitt Trigger Inverter
1 - 74HC00 - Quad NAND gate
1 - CD4071 - Quad OR gate
1 - 2N3053 - NPN transistor (may need heat sink)
1 - 2N3904 - NPN transistor
3 - 1N914 - Signal diode (1N400X will also work)
2 - 1N400X - Rectifier diodes
1 - 6.2 volt - Zener diode
1 - 3300uF - Filter Capacitor - 16 volt
1 - Power Transformer - Radio Shack 273-1365A or similar
1 - 220K 1/4 or 1/8 watt resistor
1 - 150 ohm 1/4 watt resistor
19 - 220 ohm 1/4 or 1/8 watt resistors
11 - 10K 1/4 or 1/8 watt resistors
2 - 0.01uF capacitors
4 - 0.1uF capacitors
19 - Red LEDs (15 mA)
2 - Momentary push button switches (to set the time)
1 - Toggle switch (to start the clock at a precise time)
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Tuesday, September 3, 2013

Car Battery Voltmeter with LED Indicator

The circuit was developed to create a voltmeter that will be used to test car batteries while showing an indication using LEDs.

  • Voltmeter – a device or an instrument used for measuring the electrical potential difference between two points of either alternating current or direct current electric circuit.
  • LM324 – has internal frequency compensated for unity gain, large DC voltage gain, wide bandwidth, wide power supply range, very low supply current drain, low input biasing current, low input offset voltage, large output voltage swing and differential input voltage range equal to the power supply voltage.
The voltage of a car battery can be measured with the use of a voltmeter as well as the charge left. A typical car battery voltage delivers around 12.6 V under no load condition and will require charging if the voltage reading is at 11.6 V. The measurement of voltage is best recommended during a high current like running the car head lights into high beam. In case the battery rapidly drops its voltage significantly under load, it would require a replacement.

This circuit will function as a comparator and will measure the car battery voltage with an interval or step of 1 V. The voltmeter will be connected across the battery terminals then starting the car. The voltage of the battery should not be measured below 10 V or else it will be considered as low in charge or low in water, since the water level of the battery should be about ¼ of an inch above the plates.

Car Battery Voltmeter with LED Indicator Schematic

Car Battery Voltmeter with LED Indicator

By applying the voltage of the battery in the inverting inputs of the amplifiers, the indicated voltage on the voltmeter is compared with the reference voltages that are produced by the Zener diode D1. The Zener diode is a special kind of diode that permits the flow of current in just one or forward direction as a normal diode, but will also allow in the reverse direction if the voltage is above or larger than a certain value of the breakdown voltage. The measured value is just enough to provide good thermic stability.

The presence of 10K trimmer RV1 is to adjust the degree of voltage that is required or desired while the visual indication will originate from the four LEDs.


D1=5V6 /0.5W Zener

RV1=10K trimmer

The main use of the car battery voltmeter is to monitor the life and performance of batteries. It can be mounted on the dashboard that shows the battery condition to easily monitor the electrical system voltage while driving. The measurement is done by switching off the engine as well all lights and accessories and switching on the key without starting the engine. The battery is full charge if the voltmeter reads 12 V or more while a voltmeter reading of much less than 12 V signifies the battery is either discharged or failing.
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Monday, September 2, 2013

Video Signal Amplifier Using with LH0024

The construction of the circuit has been increased to highlight and amplify video signals for further frequencies on image clarity.

Video Signal Amplifier Circuit diagram


LH0024 – IC small signal IC designed for general purpose switching and amplification due to its low voltage, low voltage and three different win the election 1N4148 – silicon small signal diode planar epitaxial used for fast switching applications with a reverse voltage of 100 V and forward current of 150 mA

Circuit Explanation

In a video output signal is the high rate of frames selected for amplification of producing a finer. This is possible by placing the track between the video device and the reception lobby, where the video port of the television receiver is inserted. The construction is done simply by exploiting the operation of three transistors instead of IC and other supporting elements.

An isolator operating in the first phase of the Q1, which provides an interface for input impedance. Q2 manage the second phase, which leads to the common base configuration. In this phase, determine the earnings TR2 250 ohms cutting the lawn. To adjust TR2, it must be placed where an output voltage of 1 Vp-p is present, with a load of 75 ohms. The frequency response is regulated by a combination of R6, C3, and 500 ohms TR1. An output buffer is completed by Q3 of the third phase which provides an airline pilot with 75 ohms. The range of the circuit is stabilized with 12 V and 50 mA.
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Sunday, September 1, 2013

Heat Detector Alarm Using the UM3561

A very simple heat detector alarm electronic project can be designed using the UM3561 sound generator circuit and some other common electronic parts . This heat detector electronic circuit project uses a complementary pair comprising npn and pnp transistor to detect heat . Collector of T1 transistor is connected to the base of the T2 transistor , while the collector of T2 transistor is connected to RL1 relay . T3 and T4 transistors connected in darlington configuration are used to amplify the audio signal from the UM3561 ic .

Heat Detector Alarm Circuit diagram

When the temperature close to the T1 transistor is hot , the resistance to the emitter –collector goes low and it starts conducting . In same time T2 transistor conducts , because its base is connected to the collector of T1 transistor and the RL1 relay energized and switches on the siren which produce a fire engine alarm sound . This electronic circuit project must be powered from a 6 volts DC power supply , but the UM3561 IC is powered using a 3 volt zener diode , because the alarm sound require a 3 volts dc power supply . The relay used in this project must be a 6 volt / 100 ohms relay and the speaker must have a 8 ohms load and 1 watt power .
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