voltage sense monitoring

Thread Starter


Joined Nov 26, 2011
please help!i need voltage monitoring circuit when i plug 110vac my first contactor will react and the contactor wont anf if i plug 220 vac power input the other contactor wont react and the previous one now react anyone have a circuit i need it badly for our project


Joined Nov 4, 2011
Hello and welcome.

I think this is a great question for a newbie like myself (I might be able to use it in the future).

I found THIS .pdf that described voltage sensing with transistors and Zeners, and it seems to be a great theoretical paper.

I'm guessing that you're looking for a circuit that gives +5V for 220 and OV for 110 right?
Then that info would be passed to a controller?

But let's wait for the experts.