12v UPS relays Trigger, 1 ~ 11v no trigger

Thread Starter


Joined Dec 9, 2006

I’m busy with some UPS circuit and I need it to switch a couple of relays on then the power is back.


Can I replace the triac with a transistor because I don’t want to let the relays on until the power is down,

I basically want a easy method to trigger a couple of relays then the mains is back, currently I’m using a 10volt reformer on a 12v relay and if the mains drop the relay drop very fast, but the transformer is to small for 3 relays and then using 3 relays I hear a buzz sounds because it probably under power, in my circuit I have a regulated power supply and a small crap 10 – 11volt power supply just to do the relay work and the regulated power supply with huge caps is for the timer section and some other components

Purpose needed for:

1 ~ 11 volt - no trigger
12 volt - trigger