Basic Start Stop Latch

Moosebreath94 · Jan 25, 2011

I am trying to learn PLC programming and I am currently working with AB Pico.

I need to stop a routine, and it would seem like the best way to accomplish this, in the spaghetti as currently nested, would be to use a basic "pushbutton stlye" start/stop latch. Instead of an operator pushing the stop button, I want to open the latch circuit with a timer or marker in place of I03.

I have tried quite a few combination's now but when I try to use a marker or timer, the latch just cycles on and off. I am beginning to think that this is related to the scan cycle.

The drawing is below, can anyone point me in the right direction?

Jim Herbert

kwires · Jan 26, 2011

your start, stop, and timer logic all have to be outside of the routine you are starting and stopping. Otherwise when you take that routine out of the scan it can never go true again. Does that answer your Question?

rdrast · Jan 26, 2011

Is your I04 Maintained? It should be a momentary TRUE to seal in M01. As long as it is momentary, anything that interrupts logic flow to M01 will drop it out completely.

Moosebreath94 · Jan 26, 2011

RD,

Yes, I04 is maintained and now I see that as the problem with the cycling. Thank you.

The actual drawing is below. I have been struggling with different timers & markers at M10, where the problem with cycling was actually at M05. I will have to try to set and reset M05, unless anyone has a better idea.

Jim Herbert
Water Treatment Engineering

tommy23t · Jan 26, 2011

Replace the M10 in line 27 with the timer contact (still NC) Once the timer is triggered (assuming the other conditions on the first rung are true and m5 is momentary), the timer will timeout and open the output. No need to use M9, it follows M6, just use M6 to start the timer. When timer times out, M6 will go off and reset the timer as well.
Not familiar with PICO, I assume the M's are internal relays.
Good Luck

Moosebreath94 · Jan 26, 2011

Thanks Tommy,

As stated, M05 is not and will not be momentary. I guess I will need to set & rest it.

M09 is used elsewhere in the program.

Yes, M are AB Pico internal relay Marker bits.

Thanks for your input,

Jim Herbert
Water Treatment Engineering

jrwb4gbm · Jan 26, 2011

Moosebreath94,
You might want to zip and post the file for better help.

Tommy,
If you are interested, here is a link to the free PicoSoft software by AB.
Link:
http://www.ab.com/programmablecontrol/plc/pico/get/PicoSoft_V6.22.zip

JHarbin · Jan 26, 2011

Moosebreath94 said:
Thanks Tommy,

As stated, M05 is not and will not be momentary. I guess I will need to set & rest it.

M09 is used elsewhere in the program.

Yes, M are AB Pico internal relay Marker bits.

Thanks for your input,

Jim Herbert
Water Treatment Engineering

If M05 is not momentary, why are you sealing around it?

tommy23t · Jan 27, 2011

Thanks, JBRW4GBM. I will do that

Moosebreath94: To remove clutter, fire M9 instead of M6. Redundant control relays will drive you nutz when troubleshooting- hard to follow. If your M5 is maintained, use a oneshot above the rung to turn the condition true for 1 scan which will latch in the output until the timer feels otherwise.
Good Luck

Moosebreath94 · Jan 27, 2011

Thanks for the advice and direction Tommy. I will get to work on it.

JBRW4GBM: I have attached the zip file of my newbie spaghetti.

Jim Herbert
Water Treatment Engineering

jrwb4gbm · Jan 27, 2011

For test purposes only, try this, use at your own risk, I have not tested this. I used your zip file as posted in post 10.
This sets up the one-shot that Tommy23t suggested.

On rung 14 position G change M05 to TT09 (Timer 9 timer), set the parameters to Single Impulse with constant set at 010.
On rung 27 position C change M05 to T09 (Timer 9 contact).

On a side note TT06 is set for 5 seconds, not 5 minutes as was indicated in the note on rung 27. I'm guessing that you probably set it to that value for testing.

Moosebreath94 · Jan 27, 2011

JBRW4GBM: These changes work great! I just set the new timer for 5 sec to be in synch with T06. The timers are set in seconds for testing purposes.

Now I can try to close out the project with alarms and display.

I think my plan for the alarms is just to nest all the alarm contacts in parallel under the E-Stop contact located on line 3, position C, just like T04 is.

Thanks for your Help.

Jim Herbert
Water Treatment Engineering

Basic Start Stop Latch

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