stan2004 posted:to drive a relay which (as I understand it) you need to momentarily "open" the secondary circuit.
I don't have the experience to say whether a relay is necessary or not. I think you or someone on this thread suggested it and it sounds reasonable. But, yes, the idea is that the secondary circuit (which is normally closed) opens briefly for a short but consistent window, and then closes again.
I bought a surplus SPDT footswitch and experimented by pressing it very slowly. Unfortunately the one I bought is a common make-make switch, and what I need is a break-then-make "slow action" switch. Even then, the duration of the open "window" would depend on how quickly the user pressed the switch down. And it's very possible that if the switch were pressed or released rapidly, the window wouldn't remain open long enough to be recognized by the target device. That's why I believe some type of timer circuit is needed, to ensure consistent operation. Using a software approach also provides the needed adjustability. Otherwise I suppose you would have to swap capacitors, resistors, etc., on a trial-and-error basis.
Really appreciate the help. If I were to approach the engineering or computer science department at a local community college, do you suppose the dean could point me to an enterprising senior or grad student, who could build something like this for a fee?
