Hello, I have a 24VAC transformer that I am using to power some rainbird water solenoids. These are activated by mechanical relays. I also have some triac modules on this same 24VAC power. Basically like this:
When I activate a relay which turns on a solenoid valve, everything is fine. As soon as I deactivate the relay, the solenoid valve causes a massive voltage spike (over 100 positive volts, and negative 300 volts). I can clearly see this on the oscilliscope - its about 10 microseconds wide.
This causes the triac modules to randomly turn on, and then turn off after about half of a wave.
My initial thought was to use a TVS diode (bidirectional).
This was the one I tried:
1.5KE36CA-TP
https://www.digikey.com/en/products/detail/micro-commercial-co/1-5KE36CA-TP/1959257
Putting the TVS diodes right at the solenoid (at location "A" in the above diagram) - this completely solved the problem. This still worked even putting it closer to the relay output.
Putting the TVS diodes right at the transformer (at location "B" in above diagram) - this did not work. I saw the voltage spike was still supressed, but the triac would still turn on occationally from the voltage spike - much less frequent though when compared to no TVS diode.
Putting the TVS diodes at the triac input (at location "C" in above diagram) - this also did not work. Same as option "B" - the voltage spike was still supressed, but the triac would still occationally activate from the interference.
So while putting the TVS diode across the solenoid valves fixed the issue, I am looking for a more ellegant solution. It is not practical in this scenario to put a TVS diode across each solenoid valve.
I tried using a 2nd transformer only for solenoids, and this also fixed the problem, but again is not very practical.
Is there a better way of handling this issue? Is it possible to isolate the "dirty" side of the power from the "clean" side of power, with a single component, or a couple components? Hopefully something smaller than a 2nd transformer which did successfully isolate this stuff. I am picturing running a wire from the transformer to some kind of a filter, then from the filter to the triac inputs. But like I mentioned earlier, the TVS diode did not seem to work reliably in this configuration.
Any help or advice on this is greatly appreciated, thanks!
When I activate a relay which turns on a solenoid valve, everything is fine. As soon as I deactivate the relay, the solenoid valve causes a massive voltage spike (over 100 positive volts, and negative 300 volts). I can clearly see this on the oscilliscope - its about 10 microseconds wide.
This causes the triac modules to randomly turn on, and then turn off after about half of a wave.
My initial thought was to use a TVS diode (bidirectional).
This was the one I tried:
1.5KE36CA-TP
https://www.digikey.com/en/products/detail/micro-commercial-co/1-5KE36CA-TP/1959257
Putting the TVS diodes right at the solenoid (at location "A" in the above diagram) - this completely solved the problem. This still worked even putting it closer to the relay output.
Putting the TVS diodes right at the transformer (at location "B" in above diagram) - this did not work. I saw the voltage spike was still supressed, but the triac would still turn on occationally from the voltage spike - much less frequent though when compared to no TVS diode.
Putting the TVS diodes at the triac input (at location "C" in above diagram) - this also did not work. Same as option "B" - the voltage spike was still supressed, but the triac would still occationally activate from the interference.
So while putting the TVS diode across the solenoid valves fixed the issue, I am looking for a more ellegant solution. It is not practical in this scenario to put a TVS diode across each solenoid valve.
I tried using a 2nd transformer only for solenoids, and this also fixed the problem, but again is not very practical.
Is there a better way of handling this issue? Is it possible to isolate the "dirty" side of the power from the "clean" side of power, with a single component, or a couple components? Hopefully something smaller than a 2nd transformer which did successfully isolate this stuff. I am picturing running a wire from the transformer to some kind of a filter, then from the filter to the triac inputs. But like I mentioned earlier, the TVS diode did not seem to work reliably in this configuration.
Any help or advice on this is greatly appreciated, thanks!