Detect 10 < x < 120vac

What I need to do is sense if the AC voltage is between about 10V and 120V. It doesn’t actually need to measure at all, I need a simple on or off. Also the upper limit isn’t really needed either.

Basically, I need to know if there AC voltage is above or below 10V or so (this number isn’t set in stone).

To make things complicated: must be a simple digital on or off. No analog, i2c, spi etc.

Space is also limited, so minimal component count is ideal. This project is contained and inaccessible so isolation from mains is not needed, but if its practical would be preferred.

Not enough information.

Maybe build a circuit around a rectifier (single diode will do in this case) and a 12-15V zener (higher than the 10V as that's rms voltage and the zener sees peaks). Not going to be very accurate in the 10V cut-off though.

Limited space and high voltages are not the best combination. You need space for proper isolation and distance between parts to prevent sparking.

bridge -> lowpass filter -> comperator

bridge → lowpass filter → comperator

Will work but you need two comparators and a logic gate, as OP asked for a signal that indicates the voltage is >10V and <120V. So there are two voltage levels that need to be tested for.

Now you are a bit picky :slight_smile:

To be a good engineer and programmer you have to be :slight_smile:

Nonetheless I do hope the OP is up to designing safe high voltage circuits. Because sudden sparking is kinda scary... :slight_smile:

bridge → lowpass filter → comperator

Figured that’d be the case. Was hoping for a simpler solution though.

A single diode instead of a bridge (i.e. half wave rectifier) will do here. That'd be a simpler solution. Simpler than that... not really.

Still wondering if a solution with a zener & optocoupler would work. Zener to switch on the opto only when the voltage is >10V. That to keep the high voltage fully separated from the Arduino.