Program help.
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Steve Bailey
Lifetime Supporting Member + Moderator
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.
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
Member
Using what exactly, a PLC I presume, in which case which one ? Show your code........
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
Lifetime Supporting Member + Moderator
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
Lifetime Supporting Member
Looks something like this
---[/]---[t1]--
T1 10
--(cmp)----(out)
T1>5
Mickey
Lifetime Supporting Member
A the free running clock will do this also. See pdf.
Or see link, last example.
http://www.theautomationstore.com/allen-bradley-plc-flasher/
Or see link, last example.
http://www.theautomationstore.com/allen-bradley-plc-flasher/
Last edited:
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
Lifetime Supporting Member + Moderator
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
Lifetime Supporting Member + Moderator
I do this with two rungs and four instructions.
Thanks steve, forgot to update that part. I noticed after my first trial. then I changes it to 2000.
Ahh so you used >=. except you start off with off, instead of on, correct?
Ken Roach
Lifetime Supporting Member + Moderator
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.
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.
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