Retentive On-delay Timer!!!!!!!!!

[cannonboy10]

ok lets see!!!

ok let me try again this time we just hope it will be alittle more expecific


(switch
I/3-----------rto----t4:0

[]------------t.base .01

---------------------preset 1200
----------------------acc----0
t4:0/en

[]----------------------------(O/1)

t4:0/DN

[]-----------------------(O/2)

I/4(switch

[]--------------------------(res)

what I have to modify in the program above so that the timer does not reset when the timer rung is false,but if the power fails,output 2 does not re-energize unles a separate start button is pressed. The accumulator must hold its value during the power failure. I been trying to figure these out but so far I can't get it to work like I been ask to. thanks to all of u guys ...

 

[Allen Nelson]

OK. I think I see what you're after. Under normal operating conditions, you want O:2/2 to come on after a 12 sec delay of I:0/3 and stay on until I:0/4 is ON. But, in the event of a power failure, you don't want O:2/2 to come ON.

Noramlly you would just RES the RTO on PLC powerup, except that you don't want to lose the .ACC value during the PLC power down time, so that solution is not the answer.

Therefore, what you need to do is build a rung that captures the event "PLC Power Failure occurred when RTO timer is Done".

HINT: Here are the pieces you need:

• A seperate address (B3/0 ?) for that event.
• The Latch (OTL) and Unlatch (OTU) instructions, which, like the RTO retain their status through a PLC power failure.
• The PLC "First Scan" address: S:1/15 This bit is active only for the very first scan of the PLC. Alternatively, you could build your own:

   B3/4       B3/3 = Active only on first scan of logic

---|/|---+-----( )

         |

         |    B3/4

         +-----( )             

Batteries not included. Some assembly required.

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