IDEC - Will you pl help me?

Today I am programming IDEC make PLC type FC4A-C24R2.

I want to program a timer. But I feel no retentive timer is in the program. In case power goes, PLC has to remember the time consumed for the process and the remaining time. Once power comes back, PLC may have to work for remaining time.

Pl help.

Jayesh Shah

I would actually use a register and increment a number in that case. Simply use a clock pulse (there should be several in the PLC) to increment a value. When you want to reset it, move a 0 into the register. This should work for any PLC. I am not familiar with the addressing in the FC4A to know where you might find a 1-sec pulse bit, but I would expect one exists. And most data register should be able to be backed up through power loss.

There is no retentive timer, however you can use counters and data registers as retentive.

If you used a counter with a 100ms pulse this would give you a total time elapsed, and this would be kept if you made the counter retentive. When the PLC restarts it can then start the counter increasing again upto the preset value.

You can also make the preset value variable by using a data register if needed.

You can also make internal relays retentive.

As you are using the C24R2 why not put a UPS on it and have an input triggered off a monitoring relay to pause the program whilst the power is down and the process isn't running? This would be a better solution rather than having the PLC powering down and restarting if outages are a regular occurence.

Jon.

In your manual index see: "Keep designation".

This will allow you to designate a register as "keep" or "clear" when the cpu stops. Select a register, and designate it as "keep". Timers don't seem to be listed as candidates for "keep" designation.

Use a "move instruction" to insert a preset as needed.

Use the "add" instruction for an up timer, or "subtract" instruction for a down timer.

Precede the Add or Subtract function with a SOTU so the function only happens once per time pulse.

Select a time pulse from: M8121 = 1-sec, M8122 = 100msec, M8123 = 10msec, When the conditions to "time" are all true, AND the selected "pulse" goes true, the register will increment (or decrement) and therefore "time" the operation.

You then will use a "compare" instruction to determine when you have arrived at your "time".

Edit: As JonR mentioned the same can be accomplished with a counter, which can ALSO be given a "KEEP" designation.

Stationmaster