So i made a small diddley bow today, and the pickup on it is just a nail with magnets on the bottom and a load of copper wire wrapped around it. This is then connected to an output jack that has 3 wires, im assuming they are output, input and power. However, when connected to an amp i cant get any sound out of it. i am a complete noob when it comes to electronics, i have no idea what im really doing. Any ideas to why this might be? thanks.
Reading some basic information about how pickups work would probably help. There are a lot of rookie mistake red flags here, and it's tough to troubleshoot if you don't understand the basics. Otherwise, a picture of what you've got might help us out.

The output jack doesn't need three wires. There's a signal and a ground, that's it. Input/output/power make no sense here, it's a passive, one-way device. It's standard to use the sleeve for ground and the tip for the hot connection. If you have a stereo jack with three tabs, just ignore the ring connection. I don't know where your third wire came from, but you should just have the start and the end of the same wire that's wrapped around the coil.

If you just used whatever copper wire you found lying around the house, that's never going to work. Pickup wire has to be insulated, and is very thin to get enough inductance. You can't use bare wire and you can't use the thick jacketed stuff you'll find at hardware stores - it's a very specific product. You're also going to need a bobbin of some sort to wind the wire around, I can't imagine winding around a nail is going to work. You'll short out the coil. While we're on the coil, the geometry/orientation matters. Do you understand the direction of induction? If you think of the coil as a magnifying glass, with the coils forming the outer rim, you need the "glass" to be facing the string. You can't just point it off any which way and expect to see something through it. If the nail has magnets on the "bottom" (where is that? unclear) then I have to guess that the coil is not facing the correct direction. Let's ignore the magnets for now, but you can't just use any random magnet for this application, either.

It's probably going to be a lot cheaper and easier to just buy a used pickup than it is to re-invent the wheel with shoddy parts. I wouldn't be surprised if your local guitar shop has some old pickups lying around from upgrading instruments, or you could put out a $5 ad on craigslist and end up with one. You can wind your own pickups but I don't see what the benefit is here. You can find a cheap pickup for less than you'd spend on pickup wire and it'll work right away.
A half-pound spool of 42-Ga Heavy Formvar Pickup Coil Wire will cost in the neighborhood of $30 from one of the usual retailers (much cheaper wholesale or in larger spools), and will give you enough wire for 6-7 single coil pickups. A Strat pickup kit (no pickup wire) will run about $15, but if you're doing DIY stuff, check this out:

Cigar Box: Build a Guitar Pickup in Under Five Minutes for Less Than $2:


They're "repurposing" a wall wart to the task.
Last edited by dspellman at Apr 10, 2016,
That's interesting, thanks. However, my mate at the music shop will give me workable junk pickups for free.

An old transformer would be a source of useable wire for a homely pickup, and since it is, I assume, just a single string, there is a lot of design flexibility.

Although I am a dedicated tinker I have never felt the urge to try pickup winding, a lot of pickup modding, but, there plenty of good stuff already out there to use as a starting point.
The problem with reusing old wire for pickups is that anything thick enough to salvage and not break is probably too thick to be decent pickup wire.

The use of a relay for the coil is kind of neat, but I doubt it's anything more than a grungy novelty. If that's an aesthetic choice (not impossible in the diddley bow world) that's an option, but where practicality is concerned it's probably not a winner. As has been mentioned, junk-drawer pickups are easy enough to come by, and most of those will likely work a whole lot better than the relay recycled version. You'll notice that a lot of the more well-known cigar box players are using piezo or off-the-shelf pickups (or at least properly constructed homemade versions), even though it's very fashionable to hack something together in those circles. That suggests to me that these thrown-together pickups are exceptionally crappy. If they were crappy in the fun, grungy sort of way I bet they'd be fairly popular.

The original versions of single coil pickups were slapped together mostly to be cheap and easily manufactured, so it's not like they're particularly refined devices. Anything more crude is probably remarkably shitty. Not that that's necessarily a bad thing, but I imagine at some point it gets in the way of making music.
^^^^ You can go thicker than typical of modern guitars if you have the working space. My prewar Rick horseshoe has a huge coil of #36, and the resistance is around 2.2 K ohm. It works very well though. In terms of tone I don't think that there has been any overall improvement in them, though their size and shape isn't well suited to Spanish-position guitars
Quote by Tony Done

Although I am a dedicated tinker I have never felt the urge to try pickup winding, a lot of pickup modding, but, there plenty of good stuff already out there to use as a starting point.

Pickup winding takes place in a lot of different ways...

Hm, must be an early prototype. Winding a guitar pickup with a bass rod.

...I'll show myself out.
thanks for all the help, i think i have a combination of every problem listed. do you thing using a small speaker as a microphone inside the can for the bridge would work? ill try it anyway, but just wondering what it might be like