Hi all,
I have a large machine (keg washer) controlled by a Raspberry Pi (actually the Pi Compute 3+ with IO Module). I was previously having issues with my power relays (24VDC coil) that control high amperage 220V power accidentally triggering some of my Pi's GPIO push button inputs.
I added diodes across the relay coils and it pretty much solved the issue. Diodes were 30V 1500W (mouser link)
But I've been testing the machine more than ever recently and unfortunately the false input trigger issue happened again. I've been testing it a few times more today and could not get it to repeat so apparently the issue is rare - but I really don't want to settle for rare. I'd prefer to fully solve this issue.
So my question is if I am already using diodes to suppress the relay coil spike, what could be a reasonable second line of defense?
One thing I might add is I recently switched from using the Pi's internal pulldowns on my push button (which I think are 20K) to using external pull downs at 10K. The issue hasn't happened since but I am not convinced the stronger pull down actually fixed it.
I attached a schematic to show exactly how the Pi activates the relays.
Component links:
MOSFET (3.3V logic level)
IDEC RELAY (intermediate relay, the datasheet says it has surge suppression circuit)
POWER RELAY (does not have surge protection but I added diode)
I have a large machine (keg washer) controlled by a Raspberry Pi (actually the Pi Compute 3+ with IO Module). I was previously having issues with my power relays (24VDC coil) that control high amperage 220V power accidentally triggering some of my Pi's GPIO push button inputs.
I added diodes across the relay coils and it pretty much solved the issue. Diodes were 30V 1500W (mouser link)
But I've been testing the machine more than ever recently and unfortunately the false input trigger issue happened again. I've been testing it a few times more today and could not get it to repeat so apparently the issue is rare - but I really don't want to settle for rare. I'd prefer to fully solve this issue.
So my question is if I am already using diodes to suppress the relay coil spike, what could be a reasonable second line of defense?
One thing I might add is I recently switched from using the Pi's internal pulldowns on my push button (which I think are 20K) to using external pull downs at 10K. The issue hasn't happened since but I am not convinced the stronger pull down actually fixed it.
I attached a schematic to show exactly how the Pi activates the relays.
Component links:
MOSFET (3.3V logic level)
IDEC RELAY (intermediate relay, the datasheet says it has surge suppression circuit)
POWER RELAY (does not have surge protection but I added diode)