Posted by Marshall on 5, 2000 at 8:11 AM:
In Reply to: HELP! Ground Connection Question posted by TheWanderer on 5, 2000 at 1:34 AM:
Each button or switch will have three contacts, often labelled NO (normally OPEN), NC (normally CLOSED), and COMMON (Ground). You wire the switch between NO and COMMON. Wiring between NC and COMMON will make the switch act pressed except when you press it. If not labelled, typically the bottom is COMMON and the middle is NO and the top is NC. Since microswitches are momentary contacts, if wouldn't matter if you were to reverse the NO and ground wires, so long as you don't connect to the NC terminal.
There are two ways of wiring. In either case, one wire runs from the NO terminal of the switch to the corresponding (P1B1, P1B2, etc) terminal of the I-PAC.
In option 1, you can run a second wire from the COMMON terminal of each switch to one of the two ground terminals of the I-PAC. Either or both ground terminals may be used.
The method I prefer involves running a wire from the COMMON terminal of P1B1 to the COMMON terminal of P1B2 and so on connecting all COMMON terminals and then running to the ground terminal of the I-PAC.
Using method 2, a broken ground wire will result in all of the buttons before the break not working.
If you wire per method 2 and then run a wire from
P1B1 common directly to the ground terminal of the I-PAC (forming a loop), then one break in the ground wire would not matter, and two breaks would be required.
Hopefully, I haven't confused you too much. Good luck on your project.