SP Relay

[Kirby K. 0]

I am working on a machine that came with 'ladder' that has a few SP Relay contacts but no 'coil' that I can find. I could see where the programer might have used these to 'set up' or 'test' the program by way of forcing them ..... but ... when the machine is running, they change state. What am I missing? I dont have alot of hair left, and this one might make me totaly bald.

[GerryM 2]

The SP contacts are special relays that are fired by the PLC. There is a list of them in the manual.(page 9-5 in the 405 PLC book) http://web4.automationdirect.com/static/ma.../d4user/ch9.pdf

[Kirby K. 0]

Thanks GerryM. Now it all comes together. I didn't have access to the manual last night (mushroom worker). And to be truthful, I didn't even think to look there for the answer. It will be different tonight. Thanks.