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2.32 Handy diode tester
Circuit 81: Handy diode tester
Setup information
Install the transistor, the diode and the two resistors as shown in Fig. 2.81. The three jumper wires come
next. Check the placement on the board again and only then connect the battery.
Experiment
If everything is wired correctly, you can safely go ahead and test any kind of diode. The measuring current is
so low that the most fragile diodes won't blow. If the test diode is connected in forward-biased, the LED is
lit. If connected the other way round (reverse-biased), the LED remains dark – that would be the result for a
good diode. The diode is bad, if in both cases the LED is lit or does not turn on.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.81.
106
Components required:
1 x 2N3904 transistor,
1 x green LED, 1 x 1 Ω
resistor, 1 x 22 kΩ resistor,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Handy diode tester
Fig. 2.81:
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