How to program to repeat timer output?

Hi folks,

I'll cut right to the chase. This is what I want to do...

Green pushbutton is pressed, an output comes on for 2 secs, turns off for 2 secs, turns back on for 2 secs, and repeats this cycle indefinitely until a specific condition is met (another input).

The catch is that I am using a CLICK PLC from Automation Direct. And to my absolute annoyance, their timers in this software are practically useless for more complex applications. There are no specific DN, TT, EN, bits. You have two options: TON TOFF. However, there are two types of TONs - One you can reset the current value with an additional bit, the other you cannot reset with an additional bit (called "retained" and "non-retained")

You can understand how CLICK's timers work from this video:
https://www.youtube.com/watch?v=7VpgURVaspU


[PS. You can DL the software for free from AD's website]



Thanks in advance!

So, what have you done so far?

From watching that video, can you at least do the first 4 second after the green button is pushed?

bmillerx94 said:

The catch is that I am using a CLICK PLC from Automation Direct. And to my absolute annoyance, their timers in this software are practically useless for more complex applications. There are no specific DN, TT, EN, bits.

Click to expand...

You won't find those in hardly any PLC aside from an Allen Bradley. While they are convenient, none of those bits are really necessary, since their functionality can easily be duplicated in other PLCs that don't include them.

This sounds like a classroom project. Is it?

Hi folks,

To answer your questions (sorry I didn't quote you).

1. I can turn the output on for 2 seconds and then off with some programming but I still cannot achieve what I am trying to do. Here is an image link of turning the output (GRN_LED) on for 2 seconds with a TON...

Note: the "Fake Output A" coil is an internal control relay for programming..



2. Oh, i wasn't aware that the TN and TT bits were not "real". I have briefly used RS LOGIX 5000 and did not see them there, but i have used some simulation software (LogixPro) and had them. I thought that those were normal functions of an AB PLC. Maybe not. To answer your question, this is a senior project for my bacehlor program. I went with the CLICK because its all i can afford.

I really wish I could solve this issue.


Thanks!

The T1 bit is your DN bit in the Click. If you want an EN bit, put a parallel branch on the Timer instruction with a "coil" to an internal address. If you want a TT, well that would be EN and not DN in series.

Try adding a second timer for your off period...

Alternatively, set the timer up for 0.01 second resolution, preset for 400 units of time, make it self repeat (DN bit in series with your start command) on the timer rung)and only light the lamp when the timer accumulated value is less than or equal to 199. (Compare instruction).

Well, good, you are very very close.

Hint: You want to start the clock again once LED lights up, right? So LED would be similar to pressing the Green button, right?

They make you buy your own PLC for "senior project"? You must be some really weird college.

With most PLCs, a timer will have a single discrete output, which is equivalent to AB's DN (Timer Done) bit.

To replicate the functionality of AB's EN (Timer Enabled) bit, simply look at the status of the logic that activates the timer.

To replicate the functionality of AB's TT (Timer Timing) bit, you could either look at whether the timer is enabled, but not done, or use a compare function to determine that the accumulator is less than the preset.

Some PLC timers use two rungs of logic for timer control, an enable rung, and a reset rung. This is especially true of retentive timers, which are capable of retaining the value of the accumulator even when the timer enable input is not true.

OkiePC, I guess I never looked at it that way. Well, that clears it up. I guess ill have to use that logic in my program to see if I can write it the way I want it to.


harryting, I want the button pressed once (thats why I latched it), then the LED comes on for 2 sec, then off for 2 sec, and repeats until another switch is true.

About the senior project, no i don't have to purchase my own. In fact, I didn't even have to do a PLC senior project. My major is MFG Engineering so controls and industrial electronics is really a sub-branch of my studies. I was lent a DirectLogic PLC and have it in posession but I wanted to learn the CLICK because i plan to use it for other home projects.


Regards

Hi folks,

Back again. I've done some experimenting. So with the help and comments on how to use these timers as if they had "DN, TT, EN" etc, i have been able to understand them a little better. Thank you for that.

I'm still a bit sketchy at ladder logic so i'm not quite sure how I can achieve what my OP says. I have, however, written a small program that pulses the RED_ALRM 3 times. The alarm is ON at 3 different time intervals for 100ms and then OFF for 2 intervals at a duration of 155ms. Thus, the alarm "pulses" 3 times. I simply used 5 TONs to achieve this.

However, this is tedious and quite inefficient to do such a simple task. I'm just struggling to figure this out. I know it has something to do with a reset.


Attached I have my ladder logic. Just to clarify, I couldnt fit it all in one screenshot. Basically, when FAKE OUT_A is energized, a 2 sec delay occurs, then the pulsing sequence with the remaining timers executes.

What I hope for is to find a way that I can just use one timer and repeat the pulse over and over (or two timers, either way).


Thanks for all the help.
Regards

You can use just 2 timers to generate a 2 second on, 2 second off square wave. A "flasher timer" and a "flasher reset timer". Set both timer presets to 2 seconds.

Let the "flasher timer" being done start the "flasher reset timer" and let the "flasher reset timer" being done reset the flasher timer.

Once you have that, then you only need to latch and unlatch a "run permissive" bit with your pushbuttons to start and stop the sequence.

Earlier, I misspoke about the timebase. 0.01 seconds is not an option but 1ms is. See if this gives you an idea:

Hi!

I have successfully got this to work with Bit_Bucket_07's flash timer reply. Such a simple concept, I don't know why I hadn't tried this. I'm not used to using timers with reset capabilities. Thank you very much for the help!

And thanks to all others who have contributed to the post. I always can rely on plctalk forums. I think I am ready to sit down and write some ladder!








Regards

There are usually several ways in which to program the same thing.
Here is the same thing but using the Drum instruction in the Click.

http://accautomation.ca/click-plc-drum-instruction/

https://www.youtube.com/watch?v=1_LUSZwADiM

Regards,

Hi,

I have tried to use the drum instructions, which is a really cool feature of the CLICKs but I couldn't quite figure it out. Although I didn't give it sufficient effort.

Thanks for the reply.

Here is another way using a counter and the pulse bits in the Click PLC.

Regards,