I have two Bond guitars, one that is 100% original and one that was found unfinished at the factory after it closed. The second one was missing its 80's electronics, but had pretty much everything else. Most Bonds end up being made into passive guitars when the electronics eventually fail, but I had an idea...
As it was incomplete, I decided to bring this one into the next century and instead of attempting to find replacement electronics from the 80's (which would be impossible in any case) I would design and code a new Arduino based guitar control system - the Bond Cyberglide (I may change that to a less cheesy name when I think of one).
Originally I wanted a clean analogue signal path with relays to switch signal and digital pots to change volume and tone, but then decided it would be more interesting to not bother with relays and allow the mixing of all three pickups with varying volume and tone on each. That means of course a very clean amplification path within the guitar to retain the tone.
I also decided that a built-in tuner was in order, plus touch sensitive controls and of course a full colour display to replace the 3 digit LEDs in the orginal guitar design.
I started by getting a Arduino Mega 2560, a breakout board for the digital and analogue I/O and lots of digital potentiometers and analogue amps to manipulate the pickup output.
My first challenge was that the pickup output was a low AC voltage and I needed everything to be positive voltages for the digital pots. So amplify and offset by 2.5v so that the voltage swing was between 1 and 4 volts at peak to give me some headroom. Do all the voltage and tone work at this amplified voltage, then step down for more normal instrument output. That may not be the best way to do things, but it was the first idea I had and it worked.
I also breadboarded this all and started looking at the tuner circuit and code. The tuner takes an analogue input from the amplified pickup output of the bridge pickup and feeds it into the Arduino A/D input. From there the code looks for identical slopes in the signal by sampling at a fixed rate and calculating the slope between several samples. Same slope should mean the same place in the signal. Quite crude, but it needs to be to run fast and it actually is quite accurate. I still need to speed it up and get it to lock on better, but it does get the notes right.
I would also like to get the guitar resprayed into a pearlescent white, but that may be too expensive for a prototype. Eventually though I'd like to try to industrialise this so others can copy the design for the remaining dead Bond guitars out there.
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