Does a relais need continuous power?

[vtwp]

Hi,

I have the following case: I have an external thermostat to control a fridge, with an on-board relais. Because this on-board relais is not very powerful, I use this first relais to toggle a second relais (30A) to power the fridge. Now, in addition to switching the on/off pin of the second relais, I could also interrupt the 5V line (VDD) of the second relais. That would save some energy (it will be small savings, but still). Is there a disadvantage of switching the relais power together with the on/off wire? Does it compromise the lifetime?

Best, David

[waltervl]

Depends what kind of relais you have. A NO (Normally Open) or a NC (normally closed). It defines the situation the relais is in when no power is pushed to the relais. For lifetime it has no influence.

[FlyingDomotic]

You may also use a relay with 2 coils: one will turn relay in one position, the other will urn it on the other position. There's no change if power is cut meantime. And no power consumption unless you change the state.

[vtwp]

Thanks, that is clear. I have a relais with both NO and NC, similar to this one: https://www.otronic.nl/nl/5v-hoog-vermo ... v-30a.html, and currently using the NO (because the relais says NO can handle higher currents than NC). I now switch both the VDD and trigger wire, and that works. And if it doesn't hurt for the lifetime, I just keep it like this .