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SSRs NO and NC

jgotthold

I need a dual SSR setup to alternatively power an electrolyser or a compressor from the same pressure sensor.

input is 12 Volts DC to 100 Amps

  • I think you intend that one machine is on while the other is off according to the output from the pressure sensor.

     

    The biggest DC solid state relay that farnell do is 40A.

     

    There isn't anything in the Farnell catalogue that will do this safely (ie without a risk of both devices being on together) without some extra components.

     

    They do some big relays like 2251776 that might be able to switch the load but you would need to use two since they are single pole NO types.

     

    RS have 150A DC NO relays (886-4830 but out of stock - someone will have them but they are £218 each !!)

     

    You could possibly use a ready made relay timer triggered by the pressure switch or a tiny PLC.

     

    A timer (Farnell 1895467)  could delay the ON switch of one power relay, giving the other time to turn off. I've never used such relays but it would be easy to test your rig with the loads disconnected.

     

    If I wanted to this I would make  a little controller for two of the 2251776 relays - but I don't know if you can do that yourself.

     

     

    MK

  • Hi John,

     

    You may have to clarify your parameters. Do I understand that you are trying to switch a load of 100 Amps at 12 volts or is it just your input signal that is 12 volts? 12 volt compressors that draw 100 amps seem to me to be a rare combination. Electrolyzers are not usually high wattage devices and even at 12 volts should have less than 20 Amps. As far as switching such loads for a reasonable cost I would look at automotive relays and start solenoids for some resources.

     

    John