Relay switching off after "random" time



  • Hello

    We have a process control system where we control few relays among other things. One of the relays is switching off after random time. It's randomly switched off after 5 minutes or after 10 minutes. Sometimes it works fine for a longer period of time but usually it opens itself automatically after a while. We control the relay (set to closed) only once during startup of the process and then it should remain closed. Another relay that stays on for a shorter time works ok.

    We don't have anything in our software that should cause it to be opened again.

    We are thinking that this could be due to temperature, as we are noticing high temperatures in the CPU. In fact we have high temperature alarm (CPU in 80-85 C range) in the Raspberry Pi LCD that is connected to UniPi.

    Any suggestions what to try next ? Unipi model is Neuron M503.

    Henkka


  • administrators

    Hello @henkka,
    we haven't experienced such behaviour yet. The temperature is quite high and in normal operation you shouldn't come close to the 70°C. What is your load on the Raspberry (htop or uptime will tell that).

    Best regards,
    Martin



  • As we had major schedule pressure to get things working, we ended up putting fans to push air through Neuron. This cooled down things so that CPU temp reported by Pi was around 50-55 C during our process. Neuron is installed inside electric cabin and air will circulate inside this cabin. But as cabin is made of steel, it will most likely provide enough radiation cooling. Cabin is installed to clean room environment with ambient temperature around ~22 C. This cooling however did not help to relay switching off.

    We ended up making calls to command relay closed in few places during our process and when process is in standby, we command relay closed every 30 seconds. This workaround allowed us to proceed with process. Of course, we still do not know what the root issue is and would like to know that. Since the device now installed in clean room environment, debugging it is way harder. As for load, if I recall correctly (can't access the device remotely), it's around 2. So quite high. We are running closed loop control and drawing graph to remote UI while maintaining local UI also. So quite a lot of tasks for Pi. For some devices where we have
    also used Neuron we made an C++ motion-core that keeps closed loop control for motion and separate process and UI program that talks via sockets to that motion-core. For this particular device where relay is opened everything is run in same program and we have double checked as best we can that there are no calls to open this particular relay. Installation was from latest version of Evok as of now.


  • administrators

    Hello @henkka,
    is it something you are able to demonstrate? The best thing would be, if you could send us the SD card image and we would be able to replicate the problem.

    Thanks for the answer in advance,
    Martin
    support@unipi.technology