As the prototype body for the one string electric guitar has been completed the next step is to make the pickup coil. I have previously made a 3D printed bobbin to wind the coil on so all I need now is to select the wire to be used and wind it. I have selected the thinnest wire I had, which is 'pretty thin' (that's a technical term for non-mechanical engineers like me) which I think is 32 SWG or 38 SWG. It is so thin I can barely see it, even with my glasses on. It is enamelled so that the coils do not short out. I thought about making a coil winding mechanism with perhaps a continuous rotation servo motor but then thought - blow it, I'll just try winding it by hand. I don't think I'll do that again as it took a long time and the coils are not especially neat but eventually I had something made, see below:
The wire is so thin I had trouble handling it but by being very careful I managed to avoid breaking the wire (until right at the end!). I used sandpaper to gently remove the varnish coating, which again it was difficult to see if I had been successful, even with a magnifying glass. I know that some wires are coated with a varnish that evaporates when soldered so I hoped for the best. As the wire was so thin I decided that directed connections wasn't going to work as the stressed would have been too great and the wire would break. Instead I used a pice of stripboard and added some Veropins and then wrapped the wire around the pin and soldered the lot. It seemed to work as when I measured the resistance ot came up as 112 Ohms - which seemed reasonable for a very long length of pretty thin copper wire. I had an old guitar cable in by box (in fact I have several - left over from my son) which I cut one end off and soldered to more Veropinis on the stripboard see below.
I used some black insulation tape on the pickup bobbin to create an interference fit into the wood as the hole drilled was slightly too large and then a U staple as strain relief on the guitar cable. Everything is now solid and stable and the coil wire should not break. I used a piece of white paper to cover up the bobbin and pretty thin wires to provide protection against mechanical rubbing and movement. As this is pretty much all there is to a simple electric guitar pickup I connected my Digital Signal Oscilloscope directly across the pickup coil and plucked the string. After some fiddling about with the settings I managed to obtain the waveform shown below. My DSO isn't that great as I bought it mainly for displaying digital waveforms and it's not that great at showing analogue signals. Either that or I just don't know how to get it to make good images - which is quire possible.
It is not that clear but I think the timebase setting is 10 ms per square which makes the frequency about 100 Hz. I don't know if this is good or bad.
I borrowed a guitar tuner and then realised that I did not know how to use it! I changed the 440Hz setting to 450 Hz and it then showed a tuned G string, see below. Sorry about the mess on my desk, but it's just the way I work - I can never stay tidy.
So everything the pickup and string are working and the prototype electric guitar is complete. I have since looked on YouTube on How to Tune a Guitar and realised I have used the tuner incorrectly. I think it needs to be set to 440 Hz and then the string tightened to bring it into tune - assuming that is possible. While trying to find a circuit or kit for a guitar pre-amp I stumbled across a headphone amplifier module for an electric guitar. Apparently this is effectively an electric guitar pre-amp (makes sense really) and I can plug the one string guitar directly into it and then into my left-over iPhone Amplifier/Speaker set. This should be arriving today so shortly I should have a fully functioning working electric guitar. If it all works I might try taking it down to a place where there is a proper guitar amplifier and try it out at full volume, maybe even turn it up to 11!
Assuming all this goes well I will then turn my attentions to making the wood work look a bit more like a real guitar. I'm not sure how I might do that as I'm not a wood worker of any sort and I don't have much spare wood just lying around.