I am using a relay to control a 230 VDC duct fan. Sometimes when the relay turns off my USB sound card freezes, to get it back I have to toggle the power (pull the USB cable, as it is USB bus powered). I have a lot of computer equipment and nothing else seems to be affected.
I have a diode across my relay and I have moved the relay further away from the USB sound card, the distance now is about 1.5 meter. But it is still happening. I am trying to understand why.
All computer equipment is connected through a UPS, the fan and relay circuit is not. I think that maybe the relay might be affecting the analog speaker signal going from the USB sound card. But I am surprised it is that sensitive, the sound card has never frozen like this until I got the relay installed.
Any thoughts would be appreciated, I am stuck trying to figure out a solution...
Update: After some more testing I can only get the sound card to freeze if the relay is actually controlling the fan. If the relay is controlling nothing, just turning on and off I have not been able to reproduce. But I am also not able to reproduce if I just turn the fan on and off manually with the switch.
Update 2: I disconnected the audio wire from the sound card, thinking that it might have picked up some noise. But the sound card still froze. It is very surprising that it is this sensitive.
Final update: I replaced the relay with a solid state relay as suggested. This not only made my circuit a lot easier, since I can power the solid state relay directly from the Raspberry Pi without a small 5V relay before the load relay, but it also seems to have eliminated my problem.