[Q] Omron CPM2A + SMC SY3160 Pneumatic Solenoid Valve

Hi,

I'm new to PLC so really need your help!
I'm using Omron CPM2A PLC and trying to control a SMC SY3160 24DC Pneumatic Solenoid Valve. Here I attacehd its PLC routine.



Now I can activate the valve on and off only one time using set, rset and timer function like the above.
But next I would like to activate the valve on and off very fast like digital pulses for about 2 seconds.
I know C and VB has a LOOP function to do that but I wonder if the PLC has the same kind of LOOP function to repeat the above routine for fixed time of duration.
Then I'm waiting for your any help!
Thank you,

Sunny
[email protected]

Really need more information on what you are trying to do.

20.07 is an internal bit for the CPM2A. This code should work for your one time situation as long as bit 20.07 is turned off before the timer is complete.

For the second example, how quickly do you want to turn the valve on and off? You will need to take into account the response time of the plc output and the valve.

Hope this will help.

Thank you for your quick response.
Here is more explanation about what I am trying to do with our "paddle sampler".
This paddle sampler is hooked up to the pneumatic air valve and this valve is connected to PLC output 10.00.

1. Paddle sampler moves out of stow position (0 degrees) and to collect position (~ 90 degrees) in about 2 seconds. --> Here I want to activate the valve on and off like pulse actions during 2 seconds.

2. Paddle sampler pauses in collect position for user settable time ~ 2 sec
3. Paddle sampler moves to press position (180 degrees) in ~ 2 sec
4. Paddle sampler remains until the scan head has passed, ~ 5 sec
5. Paddle sampler moves back to stow position in ~ 4 seconds. On the way to stow the sampler is purged off with compressed air or simply slids off due to the high velocity pneumatic transport air.


Time summary:
1. 2

2. 2

3. 2

4. 5

5. 4

15 sec

Then I hope it explains more about what I am trying to implement but if you need any other information also then I will answer it.
So now I belive you have any further comment or suggestion.
Thanks,

Sunny

So basically you want to rapidly turn the valve on and off until you get into position? Is that correct?

How do you know that you are in the different positions?

What is the complete part number for your CPM2A unit?


Just would like a little more information before we go too much further.

Yes, first the complete components of my system include the Omron Sysmac CPM2A-20CDR-A, NCR B100-180 actuator and SMC SY3160 24DC pneumatic solenoid valve.
And you are exactly right I only want to turn the valve on and off to move the actuator on the right position(angle here from 0 to 180 degree).
But as you mentioned the problem will be how we know the actuator is on the right wanted position. So first I want to use the fixed cycle time scheme as I mentioned above previous reply if possible. I want to test this to see if it works by next week.
Thanks, I think you are very experienced so I expect to hear more interesting next time.

Sunny

I am not sure that you will want to control this as you are describing. This will cause a great deal of wear on the plc output and the valve.

The CPM2A you have has relay outputs. Those outputs are rated for 100,000 operations. With the rapid on/off sequence the relay will be worn out with in a few days.

Options would be to simply turn on the valve for a period of time, or a better method would be to use a sensor to send a signal to the plc when the paddle is in the correct location. That way you know for sure that the paddle moved to the desired position. The timer method will not insure you are in position.

Just a thought.

Yes, as you said that's what I was afraid also but I didn't know that the PLC relay output has that small operation lifetime cycles. Then I think it is worthless to test the timer method at all. Right now I don't have any input signals because I use the timer methods. But as you said I also agree that it is possible to add a kind of contact switch on 90 degree position of the actuator so that we can confirm that the paddle moved the desired position. But I think we need to use these as PLC inputs. I will post here to ask for your possible comments as soon as I find the substitute method to replace its timer method.
Thanks a lot.

You could still use a timer, just do not pulse the output during the timing cycle. You could set a timer to turn on the valve just long enough to move to the 90 degree position.

The problem comes from the rapid pulsing of the output.

Good Luck and let us know if you have any other questions.

Please comment about this new logic!

Sorry again to bother you but I think we still need to make the output valve to be pulsing when the paddle reaches the 90 degree position and it hits the limit switch for detecting the desired 90 degree position.
Because after it reaches the 90 degree position the paddle need to start moving back and forth like oscillatiing motion and at the same time this limit switch's signal starts the Pressure or Force Transducer and wait there until when the pressure reaches the preset threshold value then the paddle rotates to all the way end 180 degree.
So here in this new scenario I wonder how I can make the ladder logic fot the valve output to be on and off somewhat radpidly so paddle moves up and down until the pressure transducer sends the stop signal for this paddle's oscillating motion. Then I would like to hear your comment for this question again.
Thank you.

Not sure I understand what you are doing.

When the paddle reaches the 90 degree position, you need to oscillate the paddle back and forth at that 90 degree position? So for example, move rapidly from 85 degrees to 95 degrees until you receive an input from a different device? Is this what you are trying to do?

Just trying to understand.

Yes, exactly you are right as you said. We now consider to use additionally a limit switch to detect 90 degree position and also a kind of pressure or force sensor to detect the paddle plate's pressure.
If the paddle reaches the 90 degree then it needs to be oscillating as you said for example between 85 degrees and 95 degrees until another input from the pressure sensor is activated. Here if I use just one valvle and the its PLC output is OFF then as you know the rotary actuator to rotate the paddle goes back to the original position (0 degree), of course if it is ON then it tries to move all the way up to 180 degrees. So I think this simple rapid on/off of the PLC output can make the paddle to be in oscillating mode. But here I could raise the questions about PLC ladder logic such as how I can make the PLC output on/off within variable time interval(~0.5 sec) continuously until another input is ON. I wonder these logics can be implemented easily in PLC ladder program so that I can test.
Thank you for your comments and please comment more about this issue

You should be able to create this in ladder with little problem. The standard TIM instruction is a 1/10th second timer.

You can set up two timers to set an on time and an off time. First timer will start the second timer and when the second timer times out it will reset the first. Time value will be important.

I would still be concerned about the cycling of the output. You may want to consider changing the plc to a unit with a transistor output.

Hope this will help.

Thank you for all your valuable comments.
Then I will write the PLC codes for the test according to your suggestions and let you know how it works. And as you recommended if I change the PLC from the current relay output to transistor output, can I have the same CPM2A model with just different output option? Or do I have to get totally different PLC model?
Thanks,

PLC model number would be either:
CPM2A-20CDT-D NPN output, PLC powered with 24vdc
CPM2A-20CDT1-D PNP output, PLC powered with 24vdc

Hope this will help.

OK,thank you for all your help again.
And I tried to test that on/off oscillating (flickering) mode using 2 timers as you recommended so far it looks working fine, now I set on/off interval time to 0.5 sec. But I still worry about that 100,000 times of CPM2A output replay life cycles as you mentioned before. Anyway when I told my supervisor about this possible issue, he didn't care so I am not sure I can use those two other Omron PLCs your recommended. But I really appreciate your great help. Thanks and I will let you know how this goes. I know I would have some questions soon again. lol