Program help.

[XxLinkxX]

Anyone know how to use comparator and timer to set up a pulsing frequency?
I've been using two timers to do this but im trying to cut down on my code.

 

[Steve Bailey]

On the first rung, a single timer that resets itself.
On the second rung, a "Less Than" comparison that controls the output pulse. One value in the comparison will be the timer's accumulated value. If you want a square wave pulse, the other comparison value will be half the timer's preset.

 

[tragically1969]

Anyone know how to use comparator and timer to set up a pulsing frequency?
I've been using two timers to do this but im trying to cut down on my code.

Using what exactly, a PLC I presume, in which case which one ? Show your code........

 

[XxLinkxX]

On the first rung, a single timer that resets itself.
On the second rung, a "Less Than" comparison that controls the output pulse. One value in the comparison will be the timer's accumulated value. If you want a square wave pulse, the other comparison value will be half the timer's preset.

How would I go about doing that? As in ladder logic. Im using Allen Bradley ML 1100. So how do I set up rung one as a reset and rung 2 for the compare. I understand in perpective what you are saying, just don't know how to put them in ladder logic term.

 

[Steve Bailey]

The TMR instruction resets when the logic preceding it evaluates as false, so use a normally closed contact addressed to the .DN bit of the timer.

 

[danatomega]

Looks something like this

---[/]---[t1]--

    T1    10

 

--(cmp)----(out)

   T1>5

 

[Mickey]

A the free running clock will do this also. See pdf.

Or see link, last example.

http://www.theautomationstore.com/allen-bradley-plc-flasher/

 

[XxLinkxX]

Thanks everyone for all your help. Currently working on it.

 

[XxLinkxX]

The TMR instruction resets when the logic preceding it evaluates as false, so use a normally closed contact addressed to the .DN bit of the timer.

Was this what you meant? I got it to work, but i'm curious if I did it correctly. I know you can do it several ways.

Basically I want it to turn on for 1 second and off for 1 second.

 

[Steve Bailey]

To have the output on for one second then off for one second your preset for T4:0 needs to be 2000 instead of 1000.

 

[Ken Roach]

I do this with two rungs and four instructions.

 

[XxLinkxX]

To have the output on for one second then off for one second your preset for T4:0 needs to be 2000 instead of 1000.

Thanks steve, forgot to update that part. I noticed after my first trial. then I changes it to 2000.

 

[XxLinkxX]

I do this with two rungs and four instructions.

Ahh so you used >=. except you start off with off, instead of on, correct?

 

[Ken Roach]

I use the ordinary Greater Than (GRT) instruction. The Greater Than or Equal (GEQ) would work as well.

When the .ACC accumulated value is 0 to 100, the output flasher bit is OFF.
When the .ACC accumulated value is 101 to 200, the output flasher bit is ON.

My preference is to have the flasher bits start in the OFF state when the controller goes into RUN mode. It's usually unimportant but it's my standard method.

If you really needed this to be super-accurate, you can use the timed interrupt routine feature of the controller, but for ordinary flashing lights, an ordinary timer is the way to go.

 

[XxLinkxX]

Agreed. Thanks guys for all your help.