Design 3Phase Sequence Change Indicator


Joined Jun 17, 2014

There is a very simple circuit from long ago that uses passive parts. I don't remember it so you'd have to find it on the web.


Joined Aug 31, 2022
3 phase Sequence change indicator(checker)? Not by microcontroller
l want to take a fault sign from this circuit to arduino
As already suggested, if you are using an arduino (which incorporates a processor) all you need is an input from the three phases to three I/O lines and some fairly simple code to determine the sequence. The most important consideration when dealing with AC mains is safety!

For each phase I'd use a potential divider - two resistors connected between the live and neutral with the the tapped low voltage into an opto isolator (diode) for safety. But be careful to check the voltage rating of the resistor with the high voltage drop - it may be necessary to implement this total resistance with several resistors in series so the voltage drop is shared between them.

Then digitalRead() the opto isolator outputs (collector connected to Arduino 5V or 3.3V depending on type) from which you can work out the sequence. Probably a diode in parallel with the opto diode to catch the negative voltage, but not strictly necessary.


Joined Jul 18, 2013
A phase sequence detector requires to monitor all three phases.
The normal action of these units is to power OFF the incoming power in the case of any reversal of any two phases etc, sensed.