Hello, all!

I have a unique situation and am unsure how to proceed.

Using a Teensy 3.2 or a 4.1 (I have both)
Is it safe and sane to use the GND or AGND pin for a shared ground with different voltages?

In my home cockpit, I am interfacing an instrument with a toggle switch and a 28VDC light which is activated by throwing the switch.

If I wire the toggle switch ground pin to Teensy without the 28VDC light (powered by a 3.3V relay), the switch works perfectly and does what its supposed to do in X-Plane.
If I wire the 28VDC light ground to a 28V negative block without going to the Teensy, the light works perfectly and does what its supposed to do in X-Plane.

In short, the toggle switch and the light share the same GROUND on the instrument.

Can I use the same GND or AGND pin on Teensy to accomplish both functions safely without causing major damage to my PC (or myself) or do I need to re-wire the instrument to make the grounds separate?

Thank you in advance for your help.

Jay
Las Vegas, NV