over voltage

Hello I have a PCB I use for testing some electronic circuits that contains several negative and positive power rails, with maximum voltages possible being -20v and 20v. The power supplies sources are LM2673 IC's and the current is limited to around 1A. I am looking for an over-voltage...

I'm looking to get some help in designing a board that takes an input voltage and confirms if the that voltage resides between V = 27.5V and V = 29.5V without an external power source. When the input voltage is between this range I would like an LED to light up. So far I've been exploring using...