Might I suggest a hall effect current transformer unit which monitors motor drive current. These units are available with outputs of 5 volts DC at full range current. This design also provides total isolation from the motor voltage.
I have considered using an opto isolator , but wouldn't that require a fixed voltage to light the led consistently without blowing it at the higher voltages?
You only need on/off information?
Quote from: MarkT on Jun 18, 2014, 12:05 pmYou only need on/off information?Thats right, i don't need to know how fast it's running, just is it running.
Do you mean "it has voltage applied" or "it is drawing current" or "it is rotating"I know it's being picky but they really are three different variables.