Trouble With Acknowledge

Hi guys!
i am having trouble with developing logic for a an acknowledge statement using push button.
It shuold work in this way, as it is pressed it should switch off main buzzer and the buzzer shuold swiched(definately) on if any input from any other sensor/detector arises at output.
What problem i am facing is i can swithc off the buzzer but if input from anyother sensor arrives the buzzer does not switch on unless its previous input is switched off or reset.

Please help me out!

Something like this perhaps used for acknowledging alarms:



one for each sensor.

Then have a parallel branch for each sensor, normally open alarm memory in series with normally closed alarm acknowledged, for the buzzer.

Once it has been acknowledged, the alarm (or in your case sensor) must go off before it can trigger the buzzer again. The reset bit could be removed if you didn't want that function. Then it would auto reset on the sensor (alarm condition in the code) going off.

How about this? Each alarm will trigger the buzzer on the false to true transition. This will keep the buzzer on until aknowledged even after all alarm conditions have cleared.

Well thanx for replying. I could not understand your logic. Anyhow i will repat my question. I need a logic to set an alarm when my input from sensor/detector/mcp arrives at plc and as i press a push button(acknwledge) it should reset(switch off) the alarm such that if any input arives it should be set on again. Now where I am having problem:-

When i press the ack button it swithes off the alarm but does not swithch on the alarm if input arrives at plc. That is is not being reset properly.
I am waiting for your help chaps!
Thanx

another way?

Need to add one shots after the alarm inputs,if you want the alarm buzzer to stop even if the alarm is still active.

Are you talking about an ACK button on a HMI panel ? If so which one ?

Not sure what you want, maybe Wildswings is the simplest.

Wildswings method:
If an alarm comes on it sets your buzzer as a one shot, pressing acknowledge (ack) turns off the buzzer, any other alarm coming on will turn the buzzer on again, pressing ack again turns off the buzzer.

For the same alarm/sensor to turn on the buzzer again it must first go off, quite simple.


Ken Moore's method:
Slightly flawed in that if the alarm condition is still active you cannot turn off the buzzer. (edit: just read all his post.)


My method:
If the alarm comes on it brings on a memory bit which remains on until the alarm is acknowledged and reset. This is taken from an old method prior to HMI's doing the ack for you, the reasoning being you cannot reset an alarm until you have acknowledged it and the alarm condition has gone.

An unacknowledged alarm would sound the buzzer, so once the Ack is pressed the buzzer stops but the alarm remains active until reset.

The buzzer sounds if the alarm memory is on and the alarm acknowledge memory is off. The use of the memory bit is used to bring someones attention to it even if the alarm condition has gone.

well guys thanx. tell me push button be used with latch and unlatch command. if yes then how.

i am not talking about ack statement from HMI its on pannel board.

husnain.mahmood said:

tell me push button be used with latch and unlatch command. if yes then how.

Click to expand...

Please explain further. What do you want the button to do?

I want to use push button for ack. some people say to use ons after placing input form push some say to use latch i am bit confused which is good. i know how latch works and i think its good but dont know anything about ons.

From RSLogix5 instruction help...

The ONS (one shot) instruction is an input instruction that makes the rung true for one program scan upon a false-to-true transition of the conditions preceding the ONS instruction on the rung.

Click to expand...

Let's look at a simple rung with a button, then a ONS, then an output. When you first push the button, the output will go from 0 to 1. When the PLC comes back around and scans that same rung again, even though you still have your finger on the button, the output will be turned off. It makes a pulse lasting as long as your scan time. The output is only on for that one scan. To get the output to pulse again, you must release the button and press it again.

If you put more than one instruction to the left of the ONS. All must be true before the output will go high.

You can create a simple sequence check by having instructions on both sides of the ONS. The output will go high only if the instructions to the right of the ONS are already true when the instructions on it's left become true (or at the same time).

I use the ONS instuction a lot to identify the beginning of an event or check for the order of 2 events.

Something to be careful of...let's say you want a machine sequence to start when an operator pushes a button, but only if the machine is in auto mode. You decide to use a ONS like this...

BUTTON --- AUTO MODE --- ONS ------ OTE

Now what if the operator is leaning on that button when someone esle put it into auto mode? The OTE will go high, starting whatever sequence you had programmed. It doesn't matter what order they happen in, just that all conditions to the left are true. If order of events doesn't matter, it's no big deal. If it does, then you must be careful what you put to the left of the ONS. Change that to...

BUTTON --- ONS --- AUTO MODE ------ OTE

Now, the button will activate the OTE only if the auto mode was already on before he pressed the button.

BUTTON --- ONS --- AUTO MODE ------ OTE

Now, the button will activate the OTE only if the auto mode was already on before he pressed the button.

Click to expand...

Probably it does work for you in RSLogix5, Wildswing, but in RSLogix500 it gives this error:

Error: Invalid OSR position! Must be last input condition on rung.

well guys

i am having problem implimenting wildswing method cause i need this suites my scenario. problem i am having is when i veify prog it gives error missing an output instruction.
i am using ab micrologix 1200(c) and software is rslogx 500.
thanx

Why don't you send us your logic, maybe we can help you

william