Hi everyone,
I am using a Raspberry Pi 4 Model B to control industrial 24V relay modules. However, I am not using an external 24V power supply; instead, I am routing the Pi's own 3.3V pin to the common power rail of the relays to use them as simple mechanical switches for 3.3V signals.
I have wired the Raspberry Pi GPIO pins directly to the relay signal inputs via a simple terminal block breakout board (no transistors or optocouplers are used yet).
The Problem:
When the GPIO pin is HIGH, I read exactly 3.3V on the line, which is correct.
When the GPIO pin is set to LOW, instead of 0V, I see a constant 1.2V leakage/floating voltage on the multimeter.
There is currently no common ground (GND) connection between the Raspberry Pi and the panel's internal structure. I suspect this 1.2V is due to a floating ground issue or feedback leakage through the relay's internal coil/status LED.
What is the best way to eliminate this 1.2V leakage and get a clean 0V when the pin is LOW? Should I use an optocoupler module (like PC817) or a transistor driver?
Thanks in advance!
