Relay for dual 147/122-style switching - Electrical question

[torea]

I just realized I never put a flyback diode on across the relay coil. Could that be my problem?

Yes it was. Put a 1N4007 diode across the coil and it works just fine. Measured 5.6VDC on tremolo, and oddly enough 19.82VDC on chorale (i.e., when the switch breaks the circuit).

Checked it out with the scope, looks more like a triangle wave than DC. But I guess it works well enough.

[Wes]

Sounds like you maybe have crappy rectification? Does the "triangle wave" ever drop to 0? If so you should get a capacitor across there, you don't want your relay ticking 60 times a second.

(I am assuming that by triangle wave you actually meant "the top half of a size wave" - stretch it with your scope to verify)

[torea]

I have a 1000uf cap there. It seems to be enough to hold the relay in place. Triangle wave might not be totally accurate, it's somewhere between that and a sawtooth. Not quite either, not quite the look of rippled DC. On the scope, it wouldn't show up unless it was on AC. Is that normal?

I was digging through some old parts and I found a small inductor I got a while back. If it's rated properly, would that be suitable as extra smoothing if needed?


Seems to switch fine for now, hopefully it holds up.