Acoustic continuity tester with transistors - Interrupted wires checker

Acoustic continuity tester with transistors - Interrupted wires checker

Reading time: <1 minut

From our point of view, no workshop is complete without a continuity tester, for quick and safe verification of connections and printed circuit routes.

The presented project is an acoustic continuity tester whose output frequency is determined by the measured resistance. Using it involves probing while searching the investigated circuit.

How does the project work?

The frequency of the tone produced by the tester decreases with the increase of the measured resistance. Thus, it is impossible to damage the components or connections with this tester, because the potential difference between the input terminals is about 8V and the maximum current is 50uA. The semi-adjustable potentiometer POT1 is adjusted so as to obtain a pleasant tone with the short-circuited input terminals.

List of required components:

1 x Breadboard test board + connecting wires
1 x R1 = 56k
1 x R2 = 10k
1 x R3 = 100 Ohms
1 x R4 = 1k
1 x POT = 5k
1 x C1 = 47nF
1 x T1 = BC547
1 x T2 = BC557
1 x D1 = 1N4148
1 x D2 = 1N4148
1 x Terminal contact
1 x Buzzer

For a better understanding of the circuit's functionality and to make this assembly on the breadboard we will need the electronic diagram presented below:

To better understand how this project works, we have attached the video below:

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