Help with alarming

Hello,

I have a control panel where there are many conditions that can produce an alarm (example: VFD 1 fail, VFD 2 fail, etc).
The control panel has a horn mounted on the panel
The control panel has an "alarm silence" push-button mounted on the front of the panel.
I would like my logic to work such that when there is an alarm condition, the horn will sound, and the "alarm silence" push-button will quiet the alarm EVEN if the same alarm persists. But, I want the horn to come back on when the alarm clears and then a different alarm comes on.

I was thinking of using a counter...example, no alarm -> 0, alarm -> 1, no alarm -> 0 ...etc.

I am using Allen-Bradley RSLogix500 for programming.

Can you guys give me tips on this? I do not want the answer, but as someone fairly new to programming I need gasoline for the fire.

Thanks, Jack

Maybe one integer value for alarm, rising edge moves new value to integer: 0=No alarm, 1 = alarm, 2 =alarm/silenced, No alarms => 0 or alarm=>1


Another way is to to use bit to sound to horn.
Rising edge of alarm set this bit
Silence or no alarms reset horn_bit...

how about paralleling all of your alarm bits and having a oneshot after each one. that oneshot would latch the output for the horn when one of the alarm bits comes on, then you can use your alarm silence to unlatch the horn. like this, you horn will always blow.

your statement is a little confusing though, do you want the horn to blow when the alarm clears? or do you just want it to blow anytime something goes into alarm.

this is the confusing part

>> I want the horn to come back on when the alarm clears and then a different alarm comes on.

we both thinked same at same time...

Check out this thread from mrplc...this is for the Logix5000 platform but the ideas are mostly relevant
http://forums.mrplc.com/index.php?showtopic=27406

This is how I do it.

have your alarm in consecutive bits in consecutive words. This will sound the alarm horn when a new alarm comes in, and make it go off when an unacknowledged alarm goes away. I didn't comment it, study and learn what the different commands are doing.

Alarms the old-fashioned Way

This is how we used to do it (see attached PDF file). When an alarm bit is triggered, the horn goes off (but not continuously, alternately on-off, much easier on the nerves). The horn stays in ON mode unitl the Silence button is presed, or the alarm condition clearns. When the alarm bit clears or is fixed, the Silence relay is reset, ready for the next alarm condition.