Zener diode tester using LM317
This circuit diagram project can be used for testing zener diode , we can measure the value of an unidentified Zener diode. This zener diode tester circuit it's centered around a common LM317 voltage regulator. The current is set to under 5mA, being calculated by the formula I = 1*25V/R, and this flows through the Zener diode being tested.
A voltmeter connected in parallel with the Zener its show the Zener voltage .
By adjusting potentiometer VR1, it is possible to vary the voltage on transistor TR1 emitter , which provides an adjustable voltage to the current limiter. VR1 is then adjusted until the LED D10 illuminates to indicate that current is flowing, when the test voltage may be read.
To measure diodes up to, say, 33V DC, it is normally to use a transformer of 30V AC output, but if you use a voltage trebler circuit, based around diodes D1 and D2 and capacitors C1 and C2,we can use a lower secondary voltage ( 10V AC).
Notatie | Valoare/Descriere |
R1 R2 Rv1 C1,C2,C3 C4,C5 U1 D1,D2,D3 D4,D5 D6-D9 Q1 |
680 ¼ Resistor 270 ¼ Resistor 22k ¼ Potentiometer 1000µF pol 10µF pol LM317 1n4004 Zener 18 V 1N4148 2N1711 |
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