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Relay options for higher power?

  • I would like to set up a small system with the following components:

    • moisture sensor(s)
    • temperature sensor(s)
    • relay switching of mains power up to 110V / 1200W

    The power relay is what gives me the problem.
    Any suggestions ?

    The applications at my house are multiple:

    1. Control of attic fans. The off-the shelf controller on the attic fans just turn them on when the attic temperature is over 80 degrees F, but I want to not turn them on unless the attic is hotter than the outside. So I want a 10-foot cable to a sensor that can be under the eaves.
    2. My wife's palm propagation greenhouse.
    • thermostat control of heating mats under the germination flats
    • thermostat control of fans, again need to ensure that the outside is cooler than the greenhouse before turning it on
    • warning when plants are getting dry

    But a 60W power limit is too little. Is there a good, safe mains power relay that I can drive with a contact closure in the Onion's relay module?

    I doubt that I am the only one with these needs.

  • Regarding the relays, maybe think about SSR (solid state relays). They're a bit more expensive but controllable with logic signals and available up to very high current - beyond 100A at mains voltages.

    The AC one also generally offer zero crossing switching i.e. switch at the 0V portion of the AC cycle.


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