Confused spindle relay

Ok first a bit of background on my setup.

I am running a 48v 300 watt quiet cut spindle on a separate power supply from the 24v unit that runs the steppers. I am controlling it from the arduino/gshield (for on/off) with an optical relay and speed controller with a pot switch for rpm control.
Normally, g code sends an M3 command to start the spindle at the beginning of a file and an m5 shuts it down and it stays off until told to run again. it does spin up momentarily when “open” is hit in UGS and it stops again.

Now for the fun part.

Just a bit ago I was shutting things down for the night an when i shut the pc down it cuts power via usb to the arduino, the relay clicks and the spindle starts! restore power to the arduino, it shuts off again.

I cannot start or stop it in ugs with m3 or m5 commands all of a sudden, its as if the relay is running opposite of what it should.
Any clue as to what just happened and how to correct it?

Ok, so I have no idea what happened or what fixed it but came out the shop this evening and everything was working as it should be… Wierd!


Nice job fixing it!

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