Basist Ladder Scructer Problem

kevilay · Oct 27, 2009

Hello Ive ran into this problem a few times wondering if there is a way around it. I have 2 inputs and I want each of the to turn on the same output and shut it off very quicky. Heres a better understanding.

I:0/0
O:3/0
I:0/1

When either of this inputs are on briefly turn the output on then off again while the input is held on

The problem Im running into is when one input is held on I have to be able to use the other input to trigger the output again rather then just hold it on.

Thanks
Kevin

bernie_carlton · Oct 27, 2009

On a rung place one input as an enable for a timer with the preset as the brief amount of ON time.

Make another rung for the other input and its own timer.

On a third rung place in parallel the 'TT' bits from the timers. Place your output as an OTE.

kevilay · Oct 27, 2009

bernie_carlton said:
On a rung place one input as an enable for a timer with the preset as the brief amount of ON time.

Make another rung for the other input and its own timer.

On a third rung place in parallel the 'TT' bits from the timers. Place your output as an OTE.

Oh why didnt I think of that. That makes sence, whats an OTE ?

kevilay · Oct 27, 2009

how do I reset the timers so it doesnt just blink?

bernie_carlton · Oct 27, 2009

An OTE is the standard output instruction usually shown as

---( )---

If the input is held on the timer will go through its TT (timing) cycle only once until released and restarted. There won't be blinking.

Note that if both inputs are pressed within the preset time of each other you will have jsut one longer output pulse.

kevilay · Oct 27, 2009

Oh ive never seen a TT command before, Ive always used the T EN bit. Wish my teacher would have showed me that. Thanks alot. Does that TT bit shut off when the timer reaches the DN bit?

Kevin

Mickey · Oct 27, 2009

kevilay said:
that. Does that TT bit shut off when the timer reaches the DN bit?

Kevin

Yes, it stops timing when it reaches its preset value.

bernie_carlton · Oct 27, 2009

TT equals EN and Not DN

As you go through your PLC career make sure to check out which items are available on any given PLC. This is Allen Bradley nomenclature. Not all PLCs have these bits. Most have a bit equal to the DN bit. Other bits may have to be derived by logic.

kevilay · Oct 27, 2009

thanks, lol i just realized i put basist ladder scructer problem, guess thats what happens when u post first thing in the morning

Basist Ladder Scructer Problem

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