stratslinger
Well-Known Member
I'm in the final stages of getting my control panel up and running, and I'm running into some weird behavior from a pair of SSR's.
I'm driving everything off of a Raspberry Pi running StrangeBrew Elsinore - and in prototype everything appeared to work great. The Pi drives 2 channels on a Sainsmart 4-channel relay array for operating my pumps, and it drives 2 SSRs for my HLT and BK. I have a manually controlled main relay to power up down the whole panel, and a pair of relays set up to cut power to either of the elements in the event the SSRs fail.
Which brings me to my problem: The SSR's are behaving oddly. When they're off (no signal is sent to them from the Pi), if I test the resistance across the high voltage contacts, I get 0, indicating an open (disconnected) circuit. When I send a signal - whether a constant signal from the Pi's +3.3v or +5v pins or a variable signal from one of the GPIO pins, the indicator light on the SSR lights up, and the resistance across the high voltage indicators goes up, indicating a close (connected) circuit. These are things I expect.
But as soon as I apply 120V AC to the SSR, whether it's active or inactive, both high voltage contacts measure 120V AC. It's as if, despite all other measurements indicating that the circuit is open, 120V is jumping across the circuit.
I've verified that there is no way that I'm back-feeding 120v to either lead - one lead is getting 120v from the main relay, and the other lead is sending 120v to the element relay, and that's the only thing connected to that side of the element relay - so there's no potential source of voltage other than the single source coming from the main relay.
Full disclosure, these are FOTEK SSR's I bought off of Amazon before I started to read about their reputation for being under-specced - but these are both spec'ed to be 40A SSR's that will drive 4500w elements - I'm not too concerned about pushing them too hard.
Now, are these both just failed SSR's? I would expect that if they failed closed then they'd measure resistance across the leads no matter what, so that's the only thing that hasme confused here.
Thanks in advance for any help.
I'm driving everything off of a Raspberry Pi running StrangeBrew Elsinore - and in prototype everything appeared to work great. The Pi drives 2 channels on a Sainsmart 4-channel relay array for operating my pumps, and it drives 2 SSRs for my HLT and BK. I have a manually controlled main relay to power up down the whole panel, and a pair of relays set up to cut power to either of the elements in the event the SSRs fail.
Which brings me to my problem: The SSR's are behaving oddly. When they're off (no signal is sent to them from the Pi), if I test the resistance across the high voltage contacts, I get 0, indicating an open (disconnected) circuit. When I send a signal - whether a constant signal from the Pi's +3.3v or +5v pins or a variable signal from one of the GPIO pins, the indicator light on the SSR lights up, and the resistance across the high voltage indicators goes up, indicating a close (connected) circuit. These are things I expect.
But as soon as I apply 120V AC to the SSR, whether it's active or inactive, both high voltage contacts measure 120V AC. It's as if, despite all other measurements indicating that the circuit is open, 120V is jumping across the circuit.
I've verified that there is no way that I'm back-feeding 120v to either lead - one lead is getting 120v from the main relay, and the other lead is sending 120v to the element relay, and that's the only thing connected to that side of the element relay - so there's no potential source of voltage other than the single source coming from the main relay.
Full disclosure, these are FOTEK SSR's I bought off of Amazon before I started to read about their reputation for being under-specced - but these are both spec'ed to be 40A SSR's that will drive 4500w elements - I'm not too concerned about pushing them too hard.
Now, are these both just failed SSR's? I would expect that if they failed closed then they'd measure resistance across the leads no matter what, so that's the only thing that hasme confused here.
Thanks in advance for any help.