Best performances are obtained with C1=470 or 1000uF and R4=12K or 10K. Due to low consumption of normal 10 or 20 lamp series-loops intended for Christmas trees (60mA @ 220V typical for a 20 lamp series-loop), very small and cheap SCR devices can be used, e.g. C106D1 (400V 3.2A) or TICP106D (400V 2A), this last and the suggested P0102D devices having TO92 case.

Parts:

R1___________100K 1/4W Resistor
R2,R5__________1K 1/4W Resistors
R3,R6________470R 1/4W Resistors
R4____________12K 1/4W Resistor

C1__________1000uF 25V Electrolytic Capacitor

D1-D4_______1N4007 1000V 1A Diodes
D5__________P0102D 400V 800mA SCR

Q1___________BC327 45V 800mA PNP Transistor
Q2___________BC337 45V 800mA NPN Transistor

PL1__________Male Mains plug

SK1__________Female Mains socket

Important Note:
For proper operation it’s absolutely necessary to employ high Gate-sensitive SCRs.
If you are unable to find these devices you can use Triacs instead. In this case the circuit operates also with relatively powerful devices. A recommended Triac type is the ubiquitous TIC206M (600V 4A) but many others can work.
Note that in spite of the Triac, diode bridge D1-D4 is in any case necessary.

source : redcircuits.com

To use the circuit, first, attach the electrodes to the back of the subjects hand, about 1 inch apart. Secondly, adjust the meter for a reading of 0. Ask simple questions that you know he lying or not for calibration. After that ask your main question. You know the subject is lying when the meter changes.

source : http://www.hackcanada.com/ice3/wetware/lie_detector_circuit_2.html

© randylinscott

This probe is designed for TTL circuits but you can modified for CMOS circuit. How to use it? Connect power source 5 volt to to Audible Logic Probe (you can use power source of circuit that being test). Clip the ground input of the probe to the ground of the circuit being tested. The other input lead is used to probe the different chips of the circuit being tested. The project use LM339 (comparator) as main component.

source : http://home.maine.rr.com/randylinscott/feb99.htm

Attention: This Circuit is using high voltage that is lethal. Please take appropriate precautions

How to calculate transformer rating
The basic formula is P=VI and between input output of the transformer we have
Power input = Power output

For example if we want a 220W output at 220V then we need 1A at the output. Then at the input we must have at least 18.3V at 12V because: 12V*18.3 = 220v*1

So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A.

Designed by Ashad Mustufa

The circuit above will eliminate these problems by monitoring the battery’s condition of charge through its retroactive control circuit by applying a high charge current until the battery is completely charged. When charging is complete, it turns on the red LED (LD2) and deactivates the charging circuit. This circuit is drawn to charge 12V batteries ONLY. Certain emphasis should be taken when wiring up this circuit. They are the connections of the transformer to the circuit board, and those supplying current to the battery being charged. These connections should be made with cables having a large cross-sectional area to prevent voltage-drop and heat build-up when current flows through them.

Adjustment
After assembling of the circuit, adjust TR1 to null value, power-up and make the following adjustments :-

[1] Without connecting the battery check that the 2 LED’s are turned on.

[2] Connect a car battery to the circuit and check that LD2 is OFF and a current (normally 2A to 4A) is flowing to the battery.

[3] Adjust TR1 until LD2 turns ON and the charge current is cut.

[4] Adjust TR1 to null value and charge the battery using the hydrometer technique (if you do not have or do not know how to use a hydrometer, then use a good condition battery and charge).

Carefully adjust TR1 so that LD2 begins to turn ON and the charge current falls to a few hundred milliamps (mA). If TR1 is set correctly then in the next round of charging you will noticed LD2 begin to flicker as the battery is being charged. When battery is completely charged, LD2 turns ON completely.TR1 does not need further adjustment anymore. Q1 is connected in line with the battery and is fired by R3, R4 and LD2. The R2, C1, TR1 and D2 sense the voltage of the battery terminal and activate Q2 when the voltage of the battery terminal exceeds the value predetermined by TR1.

When an uncharged battery is connected, the terminal voltage is low. Under this circumstance, Q2 is turned OFF and Q1 is fired in each half cycle by R3, R4 and LD2. The Q1 functions as a simple rectifier and charges the battery. If the battery terminal voltage is increased above the level that had been fixed by TR1, then Q2 shifts the control of Q1 gate. This deactivates Q1 and cuts off the current supply to the battery and turns LD2 ON indicating that the charge has been completed. Q1 and bridge rectifier GR1 should be mounted on heatsinks to prevent overheating. M1 is a 5A DC ammeter to measure the charge current. Optionally a voltmeter can be connected in parallel with the battery, however it must have a high input resistance so as not to influence the measurement.

Source : http://users.otenet.gr/~athsam/car_12v_battery_charger.htm

Protection in electronic circuits is crusial factor. especially polarity reverse protection. Can you imagine what happen if our circuit not pretected to reverse polarity supply. All digital IC will be damage, and also electrolit capacitor will blow up. via circuit electronic

This is may be the simplest radio transmitter that you will find anywhere. lt has a total of fiye parts and can be constructed into a very small space. It is great for science fair projects or other science related projects where short range transmission is useful. via electronic circuit