/diy/ - Do It Yourself

>>2704954
Irrigation pipes might be quite narrow, getting the on-wire probe down the pipe might prove difficult beyond a metre or two. If you can flush it down using water flow it might be doable though, so long as the fishing line it's tied to doesn't get snagged and break.

If the pipe itself is metal then it's probably far easier to detect it with a more conventional metal detector, if not by connecting a signal generator to the pipe and using non-contact voltage sensing on a probe to detect it. It may be worth investing in making some sort of receiving antenna that's directional with respect to its sensitivity (think a really long thin metal detector coil pair, or mmultiple coil pairs like a humbucker), that way you can pick up the pipe's directionality. Directional sensing would make it a lot easier, and this may also be a feature you can build into an emitter+receiver setup.

For the antenna driver, you'll want to ensure that the driving circuit is resonant, that will minimise the energy loss and prolong the battery life. You can drive an inductive load quite easily by combining a half-bridge, a schmitt inverter, and a capacitor. The inductive antenna and capacitor form a low-pass LC filter, the half-bridge drives this, the inverter takes the output of the filter and feeds it back into the half-bridge driver's input. A resistor and some clipping diodes before the inverter is a good idea.