Pulse Train

carlisn · Jul 11, 2014

Hello everyone, is there a way to simplify this program using maybe 2 or 3 commands only? I need to add even more pulse trains but the program then becomes too long!

Luke_Mages · Jul 11, 2014

could you simply use compare instructions?

carlisn · Jul 11, 2014

Probably but how...? The ladder should create a simple pulse train.

Luke_Mages · Jul 11, 2014

would something like this work? you can tailor the lim instructions to create whatever pattern you need.

carlisn · Jul 11, 2014

Ok I'll try that and let you know if it works or not. Thank you.

cornbread · Jul 11, 2014

What about using the internal clock?

Lancie1 · Jul 11, 2014

Ok I'll try that and let you know if it works or not.

Using one timer will work, and if we knew what your pulses should look like, then someone could work out the LIMs for you. I will try to run your program on the LogixPro simulator and see what it does.

EDIT: Your program does this:
1. When Start bit goes ON, nothing happens for 1.5 seconds, then the Output goes ON.
2. Nothing else happens until the Start Bit B3:0/0 goes OFF, then after 1.5 seconds, the Output goes OFF.
3. That is all it does. I am sure there are simpler ways of going that!

If you told us the nature and purpose of these "pulse trains", then we can come up with some good suggestions.

Here is one way to simplify your program: remove the extra timers that are not doing anything.

Lancie1 · Jul 11, 2014

Studying the original program, it appears that you might be trying to come up with a way to start up a sequence of equipment, then shut that same equipment down in the reverse sequence. If so, a good easy way is to set up two timers, a TON "START-UP TIMER" and also a TON "SHUT-DOWN TIMER". Then use Start-Up timer LIMs in your start circuits, and for Shut-Down use a Shut-Down Timer TT bit in series with a LEQ for each piece of equipment. That way only 2 timers can start up and shut down any number of motors or devices.

I have examples that I can post, if this is what you are trying to do.

carlisn · Jul 11, 2014

Lancie1 said:
Studying the original program, it appears that you might be trying to come up with a way to start up a sequence of equipment, then shut that same equipment down in the reverse sequence. If so, a good easy way is to set up two timers, a TON "START-UP TIMER" and also a TON "SHUT-DOWN TIMER". Then use Start-Up timer LIMs in your start circuits, and for Shut-Down use a Shut-Down Timer TT bit in series with a LEQ for each piece of equipment. That way only 2 timers can start up and shut down any number of motors or devices.

I have examples that I can post, if this is what you are trying to do.

Thank you guys, Thank you again Lancie! This is a graphical representation of what I'm trying to accomplish. My solution works but too many timers... B3:0/0 is connected to an OSR so B3:0/0 is really always a short pulse.

carlisn · Jul 11, 2014

carlisn said:
Thank you guys, Thank you again Lancie! This is a graphical representation of what I'm trying to accomplish. My solution works but too many timers... B3:0/0 is connected to an OSR so B3:0/0 is really always a short pulse.

Here is a better resolution ladder program screenshot showing the OSR added.

daba · Jul 12, 2014

Carlisn, you can do this with just two instructions....

Put an SQO in an STI file...

The other instruction is to OTU the SQO control's .EN bit, otherwise it locks up as the SQO never sees more than the first false-to-true rung transition.

Using the STI will also give you better timing accuracy. You may also need an IOM to update the output module if the pulse train has to go to an output.

daba · Jul 12, 2014

Here is how I would do it...., and the picture shows the data in the SQO data file

carlisn · Jul 12, 2014

daba said:
Here is how I would do it...., and the picture shows the data in the SQO data file

Is O:1.0 an output? I tried replacing it with O:1/0 instead which is the usual format but rslogix doesn't seem to like it... where can I take the output from?

Lancie1 · Jul 12, 2014

Here is another way using 1 timer. Only the last 2 rungs 4 & 5 are needed. The other rungs are only for setup and monitoring.

Adjust the number of pulses by changing T4:0.PRE, and the pulse width by changing the S:4 Bit up or down from S:4/0 to S:4/15. With this setup, LogixPro produced 4 pulses starting at 1.5 seconds after the Start Pulse.

carlisn · Jul 12, 2014

Lancie1 said:
Here is another way using 1 timer. Only the last 2 rungs 4 & 5 are needed. The other rungs are only for setup and monitoring.

Adjust the number of pulses by changing T4:0.PRE, and the pulse width by changing the S:4 Bit up or down from S:4/0 to S:4/15. With this setup, LogixPro produced 4 pulses starting at 1.5 seconds after the Start Pulse.

Ok great. I will try this one. The previous one you posted somehow wasn't working on my setup. I don't have a stop button wired to the plc but now I see is a good idea to have it so I will do that today. I'll let you know how it works later on today. Thanks.

Pulse Train

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