Firstly, I'm very new to electronics so please don't assume I'm not an idiot. I am.
I'm trying to link one output from a "PacLED64" (LED controller) to an Arduino Uno input.
Both boards operate at 5 VDC.
The LED controller, when it is running an LED, has a +5V out to the LED and then three inputs back that "sink" the +5V when they come on (bringing on the Red/Green/Blue channels).
I thought I might be able to just link one of the LED channels to an Arduino input - set the Arduino input to be "pull up" (so it sits at 5V) and then when I activate the PacLED this will trigger the input at the Arduino.
I wrote some code to test if the input was on or not and, when I test fire the PacLED output, this setup works "of a fashion" but it seems to be floating a bit as the input switches on it's own.
Everything I've read is talking about pull up resistors. My input pin is set as
but I wondered if I needed a "real world" pull up resistor? (see diagram below)...
If I do then what size does it need to be? I've read both 10K and 4.7K and a few other sizes?
So, my questions are:
Do I need a "real world" pull up resistor in this situation, will it help?
If I do need a resistor then what size should I go for?
Is my idea of where to connect the resistor (in the diagram) correct?
Many thanks for any help you can give me and, if you need any more information then I'm more than happy to provide it.