Mattbastard said:
I suppose a blank PCB with them two chips is a start? I can solder, that I've got down. I'll have to get my pack voltage down to reasonable levels with a voltage divider cause I assume them chips can't take 105VDC.
You can power it off a "cigarette lighter USB charger" that runs off the bike's lighting DC-DC, if there's no 5V power source in the existing bike's electronics.
PDf with the circuit and operational description.
http://pdfserv.maximintegrated.com/en/an/AN3284.pdf
You'd need to make a PCB for it cuz they're tiny parts (SOT23, surface mount). Unless you're really good at point to point wiring and have much better eyes and less shaky hands than I do.
The specific parts listed in that appnote are either 50kohm, 100kohm, or 200kohm. If the resistance you need it different, there are other digipot chips; you'd have to see if they can be used the same way.
Also you'll need an oscillator, probably run it at 5khz as that's middle of the range. Google 555 timer in astable multivibrator mode to get a bunch of pages with circuits to use to make the oscillator. Or if there's a clock signal on the bike's electronics with the right frequency you can use that.
There's a signal "lock" that has to be grounded to change the pot's value, but leaving it grounded makes the pot toggle constantly between two values. If it's a fast enough toggle (high enough clock frequency) it may not matter. It depends on what you're doing with the resistance (what is controlling it and what it controls) as to how you'll want to implement the lock signal.
On the bike right now, what specifically is controlled by the resistance? How is the resistance controlled?
