Newbie needs programming advice - Omron timer too short

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Thread Starter

Scott Boerman

Re: Programming Omron CQM1H. I need to activate an output (for 10 seconds) upon either of the following: PLC startup, of if no input buttons are pressed for 6 hours. For the startup, my first thought is to use the "always on" work bit for a timer, but for the "6 hours inactive" one, the Omron timer is max. 999.9 seconds (16.7 minutes) I guess I can have timer after timer with one timer as the input for each sequential timer, but that seems rather cumbersome and sloppy. Any advice would be appreciated. Also - the 10 second output is for a "pre-charge" valve to counteract pneaumatic cylinder leak-down to avoid "fast-starting" cylinders after leak-down. Thanks for taking the time to respond!!!!!!!!!!!!!!
 
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Juan Antonio Robles

I use a counter of minutes instead a timer to solve this problem. In this case 360 minutes.

You can use the SR bit of 1 minute tic (I'm not sure if it is SR252.00) to decrease the counter.
Bear in mind to reset the counter when appropiate to let it start again from 360.

I hope you can find this idea useful!

Regards.

Juan Antonio Robles
 
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I haven't used the CQM1 in a while, but I remember it being a great little PLC. In regards to your question, it is quite common practice to use either cascaded timers or, my favorite, using the one-second bit in the PLC (I think Omrons have this bit) to "clock" a second counter, which clocks a minute counter, etc. I believe some flavor of Omrons have real-time clocks, also, that can be used with compares to trigger events....check the manual. If you "build" your own internal clock, it can be used to do many other things in your program, including being a time base for trending, or whatever. Hope this helps.
 
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Ralphsnyder, Grayg

Set up your timer for 60 seconds.
Use the timer 'done' bit to cause a counter to count up.
Use the timer 'done' bit to reset the timer.
Set your counter to be 'done' at 360 counts (360 minutes = 6 hours).
Use the counter 'done' bit to reset the counter.
 
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David Wooden

Scott Boerman <[email protected]> wrote:
>Re: Programming Omron CQM1H. I need to activate an output (for 10
>seconds) upon either of the following: PLC startup, of if no input
>buttons are pressed for 6 hours. For the startup, my first thought is to
>use the "always on" work bit for a timer,

There is a first scan bit (P_First_Cycle, 253.15) that you can use for the
PLC startup.

>but for the "6 hours inactive"
>one, the Omron timer is max. 999.9 seconds (16.7 minutes) I guess I can
>have timer after timer with one timer as the input for each sequential
>timer, but that seems rather cumbersome and sloppy.

rather than cascading timers, you can use the same timer repeatedly and use
a counter to track how many times the time has elapsed.

>Any advice would be
>appreciated. Also - the 10 second output is for a "pre-charge" valve to
>counteract pneaumatic cylinder leak-down to avoid "fast-starting"
>cylinders after leak-down. Thanks for taking the time to
>respond!!!!!!!!!!!!!!

Hope this helps.

David Wooden
Senior Software Engineer, Systems Integration
Automation and Enterprise Solutions Group
TAS Division of Omron Electronics LLC
Office: (847) 884-7034 Extension 432
Fax: (847) 884-9383
E-mail: [email protected]
 
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