Help with rising timers.

[grimluck]

Given two temperatures and a time span, I want to create a timer that counts down to either add or subtract one from the current temperature (making a ramp). I am correctly setting TD 29 to this value (s/ 1 degree C), but the timer is never triggering the block of code. How can I fix this? Have you seen other solutions to a smooth temperature ramp? 

[Joe Tauser]

First off, break that into three  networks.  Putting a contact referencing a timer and the timer coil in the same network is bad juju.  The compiler allows it but is tripping over itself.

Put the timer coil in a network before the transitional and the resets.

Let us know if expanding the code solves the problem.

Joe T. 

[grimluck]

Hi Joe, I tried expanding the code into 3 nets a couple ways and none of them have worked yet. 

[Joe Tauser]

Put a NC of TD 29 in front of the coil and it will reset itself, giving you a pulse every 0.6 seconds.  If you're going for a 60 second pulse, you need to change your formulas to output 6000.  Timers work in 0.01 sec units.

MI 999 should have increased to 1 when the timer finished.  Make sure you're not clamping it to 0 somewhere else in your program.

You could also use the INC and the DEC blocks at the top of the Math menu.

Joe T.

[sgull]

Hi Grimluck

Is this subroutine being called in the main routine.

Not sure it will do the calculations if not called but it probably not run any outputs.

regards

Denis

 

[grimluck]

Thanks for the responses everyone, I believe that the program was using TD 29 in a way that was 'clamping' it to 0 elsewhere since deleting every other occurrence solved the problem. I am having some problems with MI 999 not reaching the value that it should (because of the delay in resetting the timer(?) ) but I think I will use a check point strategy to detect when I have reached temp 2 vs setting a timer which would be less reliable due to laggy software.