Minimal Load for PWR-SWITCH?

[markus2330]

Dear community,

I use a PWR-SWITCH where only a few adapters for MOD-IOs should be turned on/off, so the load is only a few watts.

This worked well for a year or so but now it appeared a few times that the PWR-SWITCH doesn't switch off. It is switched off via an A20. The green indicator light of the PWR-SWITCH is off. But the adapters still have power?

Something similar already happened with the a previous PWR-SWITCH so I am asking myself it there is maybe some minimal load for PWR-SWITCH? Or is it simply broken?

best regards,
Markus

[LubOlimex]

It is a relay, it doesn't matter how low is the load. The relay should turn on and off regardless.

If the LED is off but the relay is not off - then there is some issue. Maybe double check wires and level and strength of driving signal. If it is a second unit that faces similar fate maybe there is something wrong in your hardware setup.

How many times did it turn on and off approximately? Maybe it just reached MTBF?

[markus2330]

Thanks for the fast reply!

The driving signal is directly from a GPIO of the A20 LIME2 e16Gs16M with about 30cm long, very thin cables. Is this signal maybe too weak?

It probably turned on/off a few thousand times. Usually it only turns on/off a few times a day, but sometimes it was in a loop where it cycled on/off every 10 seconds for many hours. (And now this loop always happens, as turning off does not have the effect it should have.)

best regards,
Markus

[LubOlimex]

Hard to say, there are many things that might've went wrong. The wires shouldn't be a problem. But the A20's GPIO strength might be a problem.

Can the problem be from the A20 board's GPIOs? Maybe instead of toggling with GPIO, try to provide 3V from other source (TES or battery setup maybe), on the place where the GPIO goes, aka simulate GPIO high position and see if that toggles the relay.

[markus2330]

It doesn't look like A20 board's GPIO is part of the problem. Disconnecting them completely shows the same behavior: green LED off, but devices are still under power. Also with a reliable high-precision power source of 3V or 6V there is the same behavior: green LED toggles but the 230V is always on (relay does not toggle).

So probably the relay has reached the end of its life? Is it possible to replace that relay?

[LubOlimex]

Relays datasheet can be found and you can check the life expectancy but it also depends on the specifics of the load triggered. Some big loads at some frequencies can damage these faster. I've damaged relays for minutes of using wrong code that turns on and off huge load too fast.

Relays can be replaced if you are skilled. There is a lot of solder so it is easier if you have solder pump to take the solder away or at least desoldering wick (with the same goal). But if the board doesn't work for you anyway you might as well use it for practice, it can't get worse than being broken I guess.