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Continuous operation of a general purpose relay? (midwest.social)

submitted 1 year ago by [email protected] to c/[email protected]

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Hello, I have a circuit that will need to return connected hardware to a default state if power is lost. The hardware can handle continuous voltage, so I'm thinking a simple solution would be to use a battery to provide that fallback power source. To avoid draining the battery, I'd like to connect it through a relay on the normally open contact and energize the relay directly from the main power supply on my board.

Do I need to look for anything in particular to make sure the coil on the relay I choose can sustain constant voltage for potentially months at a time without damage? Or, is there another similarly low cost and simple solution you'd recommend?

The circuit runs on 12VDC from a [Mean Well IRM-10-12 (specification), and the relays I have on hand are OMRON G5LE-14-CF 12VDC (specification). I don't see anything on the relay documentation that specifies a maximum duty cycle.

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[–] [email protected] 2 points 1 year ago

With your solution using a diode on each voltage source, would there be any risk of a trickle charge draining the battery unexpectedly if the battery?

Current flows from high to low voltage, but the battery is at a lower voltage than the supply. Check the diode's datasheet for the reverse current at the voltage that would be across it. It should be negligible

Here's an example from my notes: