Do-More H2 PLC Power-Down

Hello all,

I have a slight inconvenience happening to me. I have a Do-More H2 PLC, and upon power-loss, the CPU is staying on longer than the input card, causing it to see a loss of inputs, and then triggering alarms. The alarms cut the critical functions of the machine, and change the mode to OFF mode. I am currently writing a power-up initialization program to set everything back to it's original function before the loss of power because these stations are unmanned and run mostly at night. I thought about putting timers of 20 milliseconds or so on all of my alarms, but that would take quite a bit to do, and I also don't like the feeling of delays on alarms for things like e-stops and such.

Just wanted to hear some thoughts and see if you guys had any other ideas of how to mitigate this problem.

Thanks.

I would look into an Uninterruptible Power Supply (UPS) to keep a power loss from shutting down the processor. You could also use the power on your critical inputs so they stay on too.

+1 Bullzi
Using a UPS would solve your problem and they usually provide some protection on power surges and noise. The estop circuit would then be utilized to reset the program.

Just a thought.
Regards,

Maybe you could run one input straight to power to monitor the power supply. Then, condition the alarms so they won't activate if that input isn't on. The module may have a status bit that would function the same way, I'm not sure.