Retentive On-Delay Timer

vikkaraja

Member
V
Join Date
May 2004
Posts
37
Hello Again,

I am in need of some guidance again. I am kind of stuck.I can not seem to come up with a solution yet.It is a class assignment.It uses a RTO, if during any time power is loss to the PLC. RTO accumulator must hold it's value and also upon power up DN BIT should not be enerziged. DN BIT output 2 would require another input to energize it.

Thanks.
 
Hi, I'm not sure if I fully understand the question... but the description of the RTO instruction says it gives you what you are looking for? If I have misunderstood then please explain again.

" Description
An RTO function the same as a TON with the exception that once it has begun timing, it holds its count of time even if the rung goes false, a fault occurs, the mode changes from REM Run or REM Test to REM Program, or power is lost. When rung continuity returns (rung goes true again), the RTO begins timing from the accumulated time which was held when rung continuity was lost. By retaining its accumulated value, retentive timers measure the cumulative period during which rung conditions are true."
 
Please, restate your question! Is this correct?

(1) If during any time power is loss to the PLC, the RTO accumulator must hold it's value, and also upon power up, the DN BIT should not be enerziged.

(2) The DN BIT (Rung 2, Output 2) would require another input to energize it.

Is the last sentence Statement 2 above part of your question, or a comment from YOU? Normally the DN bit WILL NOT require another input to cause it to energize. It is controlled by the timer, and will energize when the timer Accumulator value is equal to the Preset value.

To meet Statement (1), your Rung 000 does most of the job. To make sure that the DN bit is not ON upon power-up, you can add a branch to Rung 004. On the branch, put an XIC for S:1/15, the First Pass bit. Then on power-up, the RTO gets reset, so the DN bit can never be ON after a power-up.




 
Thanks for the nice explanation,but my problem is if the power goes off and DN BIT is made. I do not want output 2 to be on upon power up.I want to add another condition before output 2 is energized again.
 
Hi Lancie1, I do not want to reset the accu. value. I just do not want to have Output 2 to be on upon power restore.
 
Vikkaraja,

I really do not understand what you are doing, but if you literally want to prevent an output from coming on (but the only reason it would be ON is that the timer that YOU told to time and turn it on--has timed out) then it is really simple to do.

Add a seal-in relay. Energize the seal-in relay with your Input. The seal-in relay self-latches. When power goes on, but Input switch has not be pressed, Seal-In will be OFF.

2. Add an XIO contact from the seal-in relay to your Output rung, in series with the Timer DN bit.

I suppose this is another example of an inane, do-nothing circuit that well-meaning instructors come up with.
 
So you are saying that the RTO done bit can be on, but the Output 2 (driven by the done bit) should not be?

All you would need to do is latch a bit on with the first scan bit and put the NC contact of that bit in your Output 2 rung.
 
Ron Beaufort said:
oh, goodness ... now we're into the "silver platter" mode ... Ron Doran would never have stood for this, folks ...

but it IS almost the weekend ...

party on ...
Click to expand...

Your right...(maybe a paper plate)gone.
 
Here, I did it for you. Less aggravation that way.

RTO_SEAL-IN1.JPG
 
Last edited:
Thank you all again, it's so simple and I was not able to figure it out. I guess either I did not fully understand the istructions or I did not see the way you guys can picture it using seal in. I have alot to learn and good thing I have nothing but time.
 

Similar Topics

C
Non-Retentive Timer OFF-Delay Question
Hello guys, I am currently looking through some examples of how timers work, but this ladder logic diagram gets me really confused. Once I:1/0 is...
Replies
2
Views
1,841
ivo.maenen
ivo.maenen
M
S7 Retentive On-Delay Timer
Can you give me a suggestion for using a retentive on-delay timer within a function block that will have multiple instances? I have found two...
Replies
12
Views
6,283
JesperMP
JesperMP
E
Retentive On-delay Timer for S7-300
It seems to be a very straightforward question but I need a help.For S7 200 Micro PLCs there is a Retentive On-Delay timer(TONR) that satisfies...
2
Replies
18
Views
14,165
Alfons Gessl
A
C
Retentive On-delay Timer!!!!!!!!!
I NEED SOMEONE TO PLEASE HELP ME OR AT LEAST SOME HINTS ON HOW TO GET LOW VOLTAGE PROTECTION WITH THE DONEBIT BEEN TRUE ALL THE TIME IT SEEMS HARD...
2
Replies
16
Views
8,823
Allen Nelson
A
T
retentive on delay timers
can some tell me how they work
Replies
13
Views
3,101
504bloke
504bloke
Back
Top Bottom