I am the programmer for my team (4088A) and I am somewhat new to everything. I was just wondering if 0 on a limit switch means that the switch is up and open and if 1 means that it is closed and down.
Thanks,
Murf.
Closed is 0, open is 1. You’d think it’d be the other way around, with 0 being “off” and 1 being “on”, but for some reason it’s backwards. If anyone knows why I’d be interested to check back on this thread and find out for myself.
It’s because there is a “pull up” resistor on that pin that is tied to +5 volts.
So it shows, by default, as a “1”.
The switch makes a connection between the white wire (the CPU pin) to ground. This makes the pin ground, or “0”.
This setup is pretty common in digital electronics.
See this aricle Pull-up resistor - Wikipedia