Building a wire tracker using an Arduino Nano, a motor driver, an old laptop power adapter, an inductor coil, and an iPhone...

Because old-gen DVB-T (terrestrial) was shut down in Berlin, I recently upgraded my house to DVB-S2 (satellite). When my house was built a few years ago, the electrician installed a coax wiring in the house, but it was never used since then. Hence, there was some confusion in the cabling and I was in the desperate need for a wire tracker. I searched for some at Amazon, but they didn't get raving reviews. Hence, I thought that I should build my own. 

A wire tracker usually has two parts: a tone generator and a tone sensor. So, I digged through my treasure chests and found an Arduino Nano.

I wrote a small program for the Nano to generate a rectangular tone with frequency sliding up from 1000 Hz to 3000 Hz and then restart at 1000 Hz -- this should give a characteristic pattern to distinguish from noise. Because the Nano isn't powerful enough to generate a decent signal in a long wire, I digged up a Pololu Dual Motor Driver MC33926 that is able to drive up to 29V at 10A with a PWM switching frequency of at most 20 kHz. 

Abusing the motor driver as an amplifier, I hooked up the Nano and a 19V power adapter to the driver and got a nice strong tone oscillating at 19V. If I had wired this to a speaker, it would have push me through the roof -- you remember McFly in Back to the Future?

On the other end, I wired an inductor coil to an audio jack and installed an Oscilloscope app on my iPhone.

Let's do a dry run:

The tone generator has to be hooked to the socket:

Now, it's time to find the right wire using the sensor. The pattern is still quite strong as you can see: