Zener diode tester

Posted on Feb 7, 2014

This is a circuit to test zener diodes. It hooks up to a 120V AC line and boosts the output voltage to over 300V allowing you to test zener diodes of any voltage. The circuit also has a push button switch to triple the current, if needed. The output is attached to 2 pairs of alligator clips. One pair is to attach to the diode. The second pair is

Zener diode tester
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to attach to a multimeter. The voltage across the diode is show on you multimeter. It should be noted that this circuit could be dangerous. It is tied directly to an AC line, and has an output of 300V. The output has resistors on each line, which limits the current making it a bit safer, but will still give you quite a shock. This circuit uses the two rectifiers and capacitors to boost and rectifies the AC input voltage to about 320V DC. R4 and R5 are relatively large, and limit the output current to a small amount. So when you attach the zener diode it creates a shunt circuit, and the output voltage is set by the zener diode. R4 and R5 are relatively large, and limit the output current to a small amount. With a low voltage diode the max current is about 4mA. If you press the push-button the current is tripled. If the zener diode is large, the current will be very low, perhaps too low, so you may need to used the current tripler button. 320V is a high voltage and can be dangerous. So its important to lower the voltage to a safe level before you touch the contacts. R3 is used to discharge the bottom capacitor, and R2 is used to quickly discharge the lower capacitor when power is switched off. R1 is used to discharge the top capacitor and the neon lamp discharges the top capacitor when its voltage is above 80V. So when the switches are turned off the bottom capacitor quickly discharges and the output voltage is almost...

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