Wires are essential for conducting electricity from one place to another. These play a major role in human life. We deal with a lot of wires starting from headphones to the TV. We have all the wires running inside walls just to have a good looking wall. When something happens to these wiring like a short circuit or wire meltdown we have to replace them. But the wire is inside the wall will be very difficult to locate. In this Instructable I will demonstrate how to make wire detection stethoscope which can tell the presence of wire based on the electromagnetic energy around it.

This instrument will help electricians to detect wires underground and through walls.

Step 1: Get the Parts

1. Resistors : Pot 22K ,10K,1M, 4K7, 100K, 3K9, 1K5, 100K, 100 Ohm,10K.

2. Capacitors : 100nF 63V, 1µF 63V, 10µF 25V, 470µF 25V.

3. Diode: 1N4148

4. Microphone

5. Transistors BC 547 and BC 537.

6. 1.5V battery.

7. 3.5 mm Jack

8. Earphones to catch the sound

9. A small inductor coil 22 Gauge 4 turns and 4mm diameter.

Step 2: Circuit Diagram:

Connect the circuit as shown in the figure. I have attached a PCB design for the same if you want to make this as an instrument. 1.5V volt is required and it has very low power consumption i.e around 7.5mA. You can even connect a 3V cell. Otherwise, you can connect everything to a perf board and then solder using a standard soldering iron just like what I did here.
You can download all the required files here.

Step 3: Working

It's just an amplifier circuit with constant amplitude signal. Here the amplitude is around 1V peak to peak. For the purpose of wire finding input will be a small coil. It will receive an electromagnetic signal from the wire and wire can be detected. In this application, we cannot use metal detectors because they will detect reinforcement iron rods which are present in the wall as wires. Hence we have to use an electromagnetic field to detect the presence of wire. When it finds a wire carrying current it generates a magnetic field which distorts the signal at the input end. This results in a humming sound at the output. This can even detect the presence of wire through thick walls.

In microphone mode, this acts as an electronic stethoscope or a hearing aid with very good audio quality.

Since this circuit is 4 stage amplifier it also works as a pocket hearing aid. You can just use a microphone at the input i.e replace inductor by the microphone.

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