Quote Originally Posted by JAZZCNC View Post
I've seen this before when the voltage is close to the minimum 6v. I've also seen it when wired wrong but can't imagine you've done that. Another thing that often happens is the switch can be marked up wrong ie: NPN when should be PNP or NC when NO.

What voltage and breakout board are you using.?
The VFD cable is screened, earthed at the VFD and connected to the spindle body. Just writing that makes me wonder if there's an earth-loop because of that. Must try removing the spindle from it's bracket.

It all worked fine before I started the spindle! I'm using a basic cheapo Chinese parallel BO with diodes to isolate the 5V on it's inputs from the higher sensor voltages. I originally installed the sensors with 12V and have tried 24V but still get the same slight glow on the LEDs.

I have known issues with the BO inputs not being pulled down far enough by the sensors. I can fix that, it's the slight glow and my inability to fix it with filtering that worries me most at the moment. I was wondering if it was a known issue. If somebody is getting the same symptoms but still has the sensors working reliably I'll be happy.