Micro 820 and timers?

Hello guys- full of questions this week.

I'm working on my first Micro 820 project and wondering the best way to get a "timer timing" signal from both a TON and TOF?

Would I have to use 2 bits-- timer.IN and NOT timer.Q in series?


Or am I totally missing something? Thanks for any advice.

See attached pic
For TOF the Q will be true when timing so no need to create a TT Bit

MATT116 said:

See attached pic
For TOF the Q will be true when timing so no need to create a TT Bit

Click to expand...

Thanks Matt. With the TOF, won't Q be true the whole time the timer is enabled as well? My logic had the timer enabled the whole time a pump is on. As soon as the pump turned off, I used the TOF's TT bit to fire a purge valve to vent the line.

Q's description says "if true, total time hasn't elapsed". I assume that true then the whole time the TOF is being enabled?

By enabled are you talking about the EN/ENO? I don't use the EN/ENO so I don't know how Q reacts when using the EN/ENO.
But I have used the TOF in the exact same fashion as you are and the Q goes true when the logic preceding the IN goes from high to low and the ET is less than the PT.

Thanks Matt. I'll have to test it.

I guess when i say enabled I mean in terms of Logix 500 or 5000 where the timer is being "energized" (timer.en is on).

I did find a few more interesting instructions TONOFF and TP.

Also found the table for the TOF. Q is high as soon as IN goes high. So Q can be on even if the timer hasn't started timing.

If I were to use NOT IN and Q in series, it should be true only when timing. The TP command I found is also a while timing instruction.

I agree based on the timing diagram Q appears to be true when IN is high but in my experience that's not how it worked. Q was only true when IN went from high to low.

I have a 850 and just tried it so not sure whats up with the diagram

MATT116 said:

I agree based on the timing diagram Q appears to be true when IN is high but in my experience that's not how it worked. Q was only true when IN went from high to low.

I have a 850 and just tried it so not sure whats up with the diagram

Click to expand...

Proofs in the pudding then! lol

I'll give it a shot when the hardware arrives. Thanks for all the info.