Unitronics M90

I have a Unitronics M90 on a shrink wrap sealing machine that is giving me trouble. Last night was the first time I had ever seen the machine so my question may have a very simple answer. In the program there is a Timer T0 that controls a heater. There are some other timers in the program also. Most of the timers are set up so the presets can be modified in the HMI screen, but T0 is not. The problem is the preset for T0 is supposed to be 0.7s. On two or three occasions the preset has changed to 45 hours or more. I can't figure out how this can happen. Are there any known memory issues or bugs with this plc? I figured someone messed up entering a value in the HMI, but there is no screen associated with this time. There are no move commands in the program to put another value in the preset. I am stumped. Any advice? I will probably add another timer like T5 or T6 and see if it has the same problem.

Thanks in advance.
Glenn

I really enjoyed working with the Unitronics PLCs. I did, however, have a U90 loose the day of week. I don't know if this is symptomatic but it's worth asking the manufacturer.

You can find them on the web at: www.unitronics.com

Good Luck,

(8{)} ( .)

(Yosi)

Try OS upgrade

Hello Glen,

Anyone here can probably attest that Unitronics are my all-time favorite PLCs, and I've never heard of a bug such as what you describe.

How old is this program? Is it newly-commissioned or has it been around a few years? If new, I'd look more closely for a program bug, and if old with no previous troubles, I'd try downloading the latest Operating System (firmware). All the firmwares are backwards-compatible, and clear up bugs discovered in previous releases.

Good Luck!

TM

Thanks for the replies, I have been on vacation and just got back in the office.

The machine is fairly new from what I understand, and the first time that the problem occurred the processor was replaced.

I took a quick look at the code, but did not see a problem. I will try to attach the code for you guys that have messed with the Unitronics before. I have changed the timer from T0 to T5 in this program. This has not been tested on the machine yet, but it is the same otherwise.

Thanks,

Glenn