Preventing MSG block from continuously sending

TimD · Mar 9, 2010

Hello,

I have an ML1100. I am using the MSG instruction to send email alarms. I do not have an ACK facility (no HMI, and not using the LCD/controller for it).

I want an alarm to send an email (which I have working), but only once per 6 hours or so.

I tried using a timer, but using the DN bit *as input to TON) of the MSG instruction won't work, because the DN bit stays on, and I see no reset facility.

Any Ideas? Thanks!

PLCRookie · Mar 9, 2010

A (OSR)One shot should do what you want.

jstolaruk · Mar 9, 2010

A TON (and TOF & RTO) can be reset with the RES instruction.

TimD · Mar 9, 2010

hello,

Is there any way to reset the MSG instruction?

jstolaruk · Mar 9, 2010

If the rung condition preceding the MSG instruction is false it will disable the MSG instruction (assuming you are using it in non-continuous mode). Not sure what a RES would accomplish.

jstolaruk · Mar 9, 2010

Can post a snippet of your ladder showing the MSG instruction?

TimD · Mar 9, 2010

OH, OK, I see where a timer could cut the MSG block off. Here is my cheap, simple "one Shot" message, prevents dozens from being sent. Just have to find a way to break the MSG instruction on DN by using a timer...

TimD · Mar 9, 2010

don't worry about the ER...
It does work and goes to DN on rung completion, I have to remove the ethernet cable from the PLC to send email

(no switch onsite)

jstolaruk · Mar 9, 2010

I would do something like this

TimD · Mar 9, 2010

jstolaruk said:
I would do something like this

Thanks jstolaruk,

I'll give this a go in the morning!

Tim

TimD · Mar 9, 2010

I do think that t4:0 would never be done, since the input to the timer is always true? My timer keeps resetting itself this way. This was part of my problem earlier.

PLCRookie · Mar 9, 2010

I think that if you replace the T4/DN bit in rung #1 (in the previous post) with your B3:0/10, that it should work as you want. Rung 0 will not be needed. Curious as to why you need a timer for this?

B3:/10 triggers the instruction, the EN seals it in, then when it is Done, the DN bit drops it out.

TimD · Mar 9, 2010

PLCRookie said:
I think that if you replace the T4/DN bit in rung #1 (in the previous post) with your B3:0/10, that it should work as you want. Rung 0 will not be needed. Curious as to why you need a timer for this?

B3:/10 triggers the instruction, the EN seals it in, then when it is Done, the DN bit drops it out.

If I don't, everytime the alarm condition goes falst to true, the recipient gets another alarm.

I am trying to prevent alarms, once initiated, for a duration set by a timer, say, 6 hours. That way the maintenance staff isn't bothered every 30 min

ydtech · Mar 9, 2010

Not to worry, T4:0 will be done, resets itself and starts counting again. Look up what it does when the rung goes false, and under which circumstances it does so.

TimD · Mar 9, 2010

Thanks for all the help! Got It!

Please see attached. Now 8 hours can elapse until the alarm is allowed to re-generate. If the condition is not resolved within 8 hours, a new message is sent.

B3:0/9 "Status Email Toggle" is a runtime toggle bit for me to do testing, in real life, it would be the alarm bit.

Preventing MSG block from continuously sending

TimD

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