My can opener problem.

Hi all.
I was wondering if someone here could look this over and offer any suggestions for changes. Anything you might see as a problem.

I am using a Micrologix 1000, program using RSLogix 500. The outputs are 3 Double acting solenoids, where if one side of it is on, then the other cannot be, thus the use for location inputs. This is alos the reason why the output does not have to be latched in. This is excluding the one single acting solenoid, which has its Latch/Unlatch commands.

I've attached a rather crappy drawing of the can opener. Just for visuals. Hope it helps.
And I hope you can help me.
Thanks.

~Norm

One problem that might give you a headache is the One shot bit B3:0/2 that you energize in rung 2 with an OTE and in rung 3 you have used the OSR instruction with the same bit address. That is not recommended by AB but if it works for you then no harm no foul. I hope those double acting solenoids have time to move with the logic you show, and I assume they do with the associated inputs that give their location prior to moving. Other than that, it looks like a well laid out and simple program. If it works, then who could ask for more?

You are using an OSR incorrectly. The address which is the operand for the OSR should not be referenced anywhere else. It is only a memory of the state of the rung leading up to it. A rung which uses an OSR should be:

  

 

  LOGIC OF SOME TYPE                  OUTPUT BIT

---------||--------------[OSR]-----------( )

 

The 'output bit' will be on for one scan as the 'logic' changes from false to true. Then the 'output bit' is used as needed.

Opps. Yeah I forgot to change that. I was doing some other edits and forgot about that. So to get this straight should it look like this....?
That way it won't constantly make the other output, not until this can is cleared and another is inserted. I'm really not familiar with one shots. In fact this is the first program I've had to build, the only thing I normally do is edit.

A real world output on for 1 scan??? Be lucky if it does anything.

So can someone tell what would work to make this trigger once and not repetitively.

PeterW said:

A real world output on for 1 scan??? Be lucky if it does anything.

Click to expand...

Another problem, even if you remove the One Shot would be with OPENER IS UP i.e. the output would go off as soon as OPENER moves away from the UP sensor.

This may be a case where an OTL needs to be used for the output, then it would work even with the OSR.

It may also be necessary to use or learn about what I call WAS BITS: http://www.plctalk.net/qanda/showthread.php?t=30590&highlight=BIT

maintain the output until the other sinsor is detected or a timeout failure.

Actually I already see some faults.
For example in rung 5, the output is going to happen as soon as the can is put in, not when the can goes BACK up.

I may have to have some kind of counter, saying when this equals 1 do this, when this equals 2 do this. Would this be a feasible way to do this?

Tell me if this is any better...

Do you have a written "sequence of operation" for this? If so, I suggest you look at the logic as follows:

1) Figure out each action as a series of "steps". For example, pushing a start button initiates the first action.

2) The feedback devices (usually limit or prox switches) confirm the action and initiate the next steps while at the same time, drop out the previous step.

3) If you wish to add some kind of "dwell" timing in any step, use a timer either alone or in conjuction with your feedback device(s).

You have multiple instances of the same outputs.

You do not want to do that, use internal bits to create instances and then parallel it on the one and only output rung.

For eg. Assign B3:1/5 to retract all devices upon start button pressed for the first time. The use it (B3:1/5) in parallel to trigger all your retract solenoids.

______

The start button I assume is a momentary pushbutton which means you will have to hold it down for the devices to go home. In other words you do not really have a "START" and the only stop is the ESTOP.

I do not understand some of the devices but Rung 0008 if Pusher IN is a position sensor for Pusher pushes then as soon as it moves both outputs will turn off.

Rung 0009 will have the same problem. It is also a bad habit placing output coils on multiple rungs.

You gave a partial description of what you are doing but not enough for me to understand the outputs, can you describe what will happen thru the process? Could you also describe how the double acting solenoids work?

The ESTOP ckt is hardwired and any safety actions should work from that end, it depends but an estop usually disables the output power. You can monitor the estop in a plc to cause it to reset but (for this type endeavor) should not need to output an action. Why do you need to purge the air out of the system and how do you stop it without using the ESTOP, an ESTOP is for emergencies and should not be used for ordinary stopping.

All I can think of right now.

rsdoran said:

Could you also describe how the double acting solenoids work?

Click to expand...

Ron,

I doubt this is the exact valve he is using, but here is an example of a dual solenoid valve.
http://www.machinedesign.com/ASP/viewSelectedArticle.asp?strArticleId=59311&strSite=MDSite&catId=0

I once worked for an outfit that thought these types of valves could be used for safety. I don't work for them any more. They can be hard to troubleshoot when they get balky ( they add another layer of complexity).

milldrone said:

Ron,

I doubt this is the exact valve he is using, but here is an example of a dual solenoid valve.
http://www.machinedesign.com/ASP/viewSelectedArticle.asp?strArticleId=59311&strSite=MDSite&catId=0

I once worked for an outfit that thought these types of valves could be used for safety. I don't work for them any more. They can be hard to troubleshoot when they get balky ( they add another layer of complexity).

Click to expand...

LOL, I reckon I know what a double solenoid is but there can be differences i.e. spring loaded center return, shift maintained or could require power be applied to maintain shift. This would make a difference.
http://www.patchn.com/fluidsymbols.htm