Deadtime on a digital signal

willxfmr said:
You just need to break things down in to bite sized pieces.

1) What instruction would you use for timing the 20 seconds from the button being pressed to the output turning on?

2) What instruction would let you keep the output on for X amount of time and then turn the output off? I'll give you a hint on this one, because many people get this wrong. The TOF instruction is a tool of Satan and should never ever be used. People who say otherwise, likely hate the Packers, brats, and puppies. Don't be that person.

Sort those two issues out, and post the code you came up with. From there we can help get the rest of the issues sorted out.


Bubba.
Click to expand...
To be fare. I like brats.
 
AB ladder solution

An RA/AB ladder solution is here: https://github.com/drbitboy/plc_deadtime_fifo; ZIP archive file is attached.

It only needed one TON timer running at 1Hz; the output hold is driven by that timer.

This approach could be refactored with minimal effort to use no timers and instead use the RTC:0.SEC word if an upper limit of 59s for deadtime was acceptable; even a limit of 86,399s would be straightforward. N.B. Using the RTC with MicroLogix 1100 PLCs would drop the resolution to 2s; the RTC-based approach will not work with Emulate500.


Caveats and limitations
  • Deadtime is limited to a range of [5:125] in 5s increments in this implementation
    • It could be [1:127] in 1s increments with the HMI proposed by the OP
    • The 2**n and ((2**n)-1) size limitations can be removed via actual modulus calculations and other busier coding techniques, instead of the bit-wise AND shortcuts used here.
  • The accuracy of timing is 1s or so
    • This could be improved by decreasing the time base of the TON timer to 0.01s (100Hz), but that might result in some missed transitions.
  • The RSS file in the .ZIP archive is configured for a MicroLogix 1100 Series B on ethernet with IP=172.16.240.240*
* It also works with RSLogix Micro Starter Lite/Emulate500
 
Last edited:
Phrog30 said:
In case nobody noticed, the OP hasn't made a post since the initial one on this thread. Time well spent... o_O
Click to expand...

I did notice. It probably was homework as sussed by Lare in the first response.

That said, it was a decent learning exercise for me.

I am unsubscribed now; I'll move on to the sine thread soon, but I have to use a Chebyshev because I only have ML1100.
 
Last edited:

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