Reading LOW input

Projects General Guidance
1

I'm trying to read a LOW input provided by a door control system which normally triggers a relay (but I'm using an Arduino to receive that input instead, and send along to the relay).

So, normally the input that I'll receive will be HIGH, but when the relay is supposed to trigger, the door control system will send an LOW signal.

How do I wire up the Arduino to read that low signal? I need to keep the input pin HIGH, by connected via resistor to the Arduino 5v, correct?

Would this be the wiring....connect the input pin via resistor to 5V, and then simply "inline" have the pin/wire with the input from the door control system?

Thanks!

3

What voltage is the HIGH you will be getting? If the output drives a relay etc, it may be higher than 5V.

Weedpharma

4

So simply connect the input wire coming from the door control straight to the pin with the pull_up turned on (along with the ground from that system; need to all share the same ground, right?)?

It's 5V.

Thanks!

5

Yes, common grounds.