How to connect a GPIO to GND via relay

[stemmo 0]

Hi all,

I need to connect in the simplest mode a GPIO pin (as INPUT) to the contact of a relay (not the control pins of the replay) that connects the pin to the GND.

Of course I'm using the internal pull-up resistor but I don't know the value of this one.

Is it a problem to connect the pin directly to GND or better to use a resistor to limit? Value?

Thanks a lot!

Regards

Edited January 11, 2021 by stemmo

[maartinus 0]

Hi, you should use 2 resistors. The first one (10K) connected to 3.3V (yellow pin) and GPIO input and second one (1K) connecting GPIO input and relay contact.