Plastico

Firstly, thanks to everyone who's responded. Ken, I'll give this a try next time the machine gets shut down and see what happens.  Although the machine and PLC/IO Cards are old, the rack is only a couple of years old (had to replace it because of a bad slot).  That's not to say that the DIP Switches aren't bad or maybe a heat related issue.  I've talked to management about this and have given my recommendations, so it's in their hands...  we do have a backup of the PLC program and replacement PLC5/15 should this die, but will obviously have to get someone in to program it (unless they finally see the wisdom in getting me the software). Thanks everyone.

We have an old machine that has a PLC 5/15 (and PLC5 hardware) which is connected to a PV550 HMI via DH+.  The PLC normally has an address of 16 and the HMI is set to 17.  On occasion, when the machine is completely powered down (for a little while) and then powered up, once the HMI is fully powered up it says that there is a duplicate node address (it worked fine before power down).  It turns out that the PLC has for some reason changed its address to 17 (the HMI's address).  I currently don't have access to the PLC (no programming software ) but if I changed the HMI address (which was 17) to 16, I lose the error message (but obviously the HMI won't correctly display data).  I have to go into the HMI's program (I have that software), change the terminal node address to 16 and the PLC node address to 17, save it and download it to the HMI.  Then it works ok until the next time. It doesn't always do this.  Quick power offs don't seem to affect it.  Only longer down times (and not always). Any suggestions as to why this happens and how I can fix it (without going into the PLC - as I mentioned, no software and the company doesn't want to shell out $9000 for it). Thanks, Andrew