I'd like to use multiple LM1881 sync strippers to detect an active sync signal for use with a switching project. I have the three sync strippers connected to three different digital pins of a Uno. Each sync stripper will be connected to a composite video device using a y splitter, with the other end terminated to an Extron Crosspoint.
When I have the three composite video devices connected to the sync strippers, everything works fine: the sync stripper is returning a low signal which is read by the Arduino. And when I turn on any of the devices, the signal alternates low and high (as expected since sync is a data line).
However, I don't always want a device connected to every stripper. It would be nice if I could have any of the devices unplugged, and the digital pin read low. But when I do, the pin floats between low and high randomly.
I figured I needed a pull down resistor connected to each sync stripper output and ground to pull these pins low. I added a 10k resistor to ground, but the lines still float.
Am I missing something?