Adding a Timer to the Logic

[Ones_Zeros]

Hello,
I'm still learning PLC programming and I was needing some help with
making some changes to our program.

I'm needing to remove the (TON) timer on rung 9
policies at work have changed to were once the (GRT) instruction sees 5%
it will shut the process down.

Overview of my Task:
At this point the process has seen 5% and it is shutdown, the O2
has to be below 5% to run. Now I have to start the process to give it a chance to
come down below 5%, so I want to hit a by pass button to start a 5 minute timer,so
the process has a chance to run for 5 minutes givining the O2 a chance to come down below 5%
if with the 5 minutes the O2 comes down the timer will stop and the process will start and
if during the 5 minutes the O2 don't come down below 5% the process will shut back down.

Here is were i need some help modifying the logic:
1. I want to delete the (TON) timer on rung 9
2. I added a new rung and I want to use the same input that is tied to the Reset Button (Local:3:I.Data.6)
3. when i hit the Reset Button, i want it to start a 5 minute timer
4. During the 5 minutes it needs to check what the O2 is reading by the (GRT) instruction on rung 9
5. If anytime during the 5 minute timer is goes below 5% i want it to shut the timer off and Latch the O2_SD bit back on rung 10 so the process would start back up.
(at this point you can't tell by the pic but the O2_SD would be un latched, so it would need to be re latched)
6. If during the 5 minute timer the O2 don't go below 5% it will shut the process back down, so it would nee to unlatch the O2_SD bit on rung 10
7. Someone would have to physically hit the reset button each time to start the 5 minute timer if the O2 don't fall back below 5%, thats OK.

Here is a sample of the logic:

I hope this makes since, this is probably simple to you guy, but I'm trying hard to learn this.

Thanks again for your help

 

[Ones_Zeros]

Forgot to mention this software is RSLogix 5000
the PLC is a Allen Bradley 1769-L32E Compact Logix 5332E Controller

thanks

 

[chavak]

H,

Your attachment do not shows anything.

If you are finding hard to continue the timer for five minutes, you can use the timers "/tt" timing bit in parallel to the switch input to let the timer continue timing.

Then use the same timing bit in the following rungs to compare or perform any other logic upon timer is being timed.

Regards

 

[rdrast]

Why not just reset the actual Timer itself?
Tie the reset button to a RES instruction with the address of your existing shutdown timer (O2_Timer).

Of course, I always get worried about giving an operator an unlimited opportunity to bypass system constraints, you might give some thought to including a counter to only allow such a reset 3 times for example.

 

[Lancie1]

Why not just reset the actual Timer itself?

I agree. This is a LogixPro program, but should be similar enough to use the same instructions.

 

[Ones_Zeros]

Thanks so much for your help and time with this, it has helped me alot