Sequencer issue

italian_virus · Jan 30, 2008

Hello all,
I was hoping if you guys can help me out.
The situation that i have is that i need to control 6 pistons that have two solenoid valves (one to advance and one to retract) now i need to control these pistons in a curtain sequence. I plan on using sequencers though the catch is i CAN NOT use timers to control them. Now i have 12 outputs (solenoid valves) and 12 inputs (sensors showing when the piston is fully advanced and fully retracted). Also this must be done in RSLogix 500.

Any help would be greatly appreciated
Thanks

Lancie1 · Jan 30, 2008

Italian,

Make a try at it. Use the Advance and Retract sensors to advance the sequencer through each step.

Please explain what you mean by "curtain sequence". Do you mean that you advance Piston 1, when it is fully advanced (Piston 1 Advanced sensor made), then Piston 2 is activated, and so on until Piston 6 is advanced, then Piston 6 retracts, then Piston 5 retracts and so on until Piston 1 is retracted, at which point the cycle restarts?

ZIP you RSLogix program and post it here and we will critizize it for you--no charge!

BobB · Jan 31, 2008

I think he meant 'certain sequence'.

mordred · Jan 31, 2008

probably be a lot easier to help you if you can also explain what sequence requirements you need is it engage valvel then when valve1 disengages engage valve two etc?????

cjd1965 · Jan 31, 2008

Maybhe the pistons open and close his curtains

only joking

Lancie1 · Jan 31, 2008

I CAN NOT use timers to control them.

Is that a customer specification requirement? I don't mean to insult you, but that sounds a lot like a homework requirement....

I think he meant 'certain sequence'.

Spelling errors (and also sloppy speech) that actually make up some reasonable word cause many great misunderstandings in this old world. A "curtain" sequence seemed to make sense, if you imagine how the 6 cylinders could mimic the waving of a curtain as it unfolds. Or perhaps his customer described it this way to mean a curtain that rolls down from the top, then rolls up again (as the 6 cylinders extend one at a time in sequence, then retract one at a time)

What would be a good description for a "curtain sequence" for a bunch of cylinders?

I know just the group that can come up with one. Is the Chief Bottle Washer for the old Smoke & Mirrors Corporation still hanging around?

italian_virus · Feb 22, 2008

"The situation that I have is that I need to control 6 pistons that have two solenoid valves (one to advance and one to retract) now I need to control these pistons in a *certain* sequence. I plan on using sequencers though the catch is I CAN NOT use timers to control them. Now I have 12 outputs (solenoid valves) and 12 inputs (sensors showing when the piston is fully advanced and fully retracted). Also this must be done in RSLogix 500."

Sorry for taking so long to responded guys, I’ve been busy running errands for my client. This is the situation as of right now. I figured out that I can control my SQO (solenoid valves) by using an SQC (the input sensors I talked about before), with my SQO binary sequence one step ahead of my SQC. This is done so that the process can loop itself until the user pushes the stop pushbutton. Now this is where I have the problem. Two requirements that are needed are when the stop pushbutton is pressed all cylinders must stop in their respective positions (pretty simple) but when the start pushbutton is pressed all cylinders have to be retracted so the process can start over from the beginning. The thing is though how can I implement retracting all the cylinders on the start pushbutton without throwing off my binary sequence for the SQC and the SQO. I have added two programs that I have done so far. One has the stop button retracting all the cylinders though the bad thing to that is if the process stays off for a long period of time the solenoid valves stay on in their retracted positions, which in turn would cause them to heat up. In the other program I tried to get the start button to retract all the cylinders but in doing so it throws my binary sequence off making the SQC not able to match up with my SQO.

Again any help would be greatly appreciated
Thanks

P.S. hopefully the isn't no spelling mistakes this time around

Lancie1 · Feb 23, 2008

This is where I have the problem:

Two requirements that are needed: when the stop pushbutton is pressed, all cylinders must stop in their respective positions (pretty simple)..

but when the start pushbutton is pressed all cylinders have to be retracted so the process can start over from the beginning.

The thing is though how can I implement retracting all the cylinders on the start pushbutton without throwing off my binary sequence for the SQC and the SQO?

It is probably easier than you think.

When STOP is pressed:
1. Reset all SQO's (as you are now).
2. Reset the new staging relay (used for start-up).
That means that all Outputs go off and all cylinders remain where they were.

When Start is Pressed:
1. Inhibit SQO's until cylinders are retracted (use a staging relay),
2. Then Retract all cylinders one time, then
3. Enable SQO's and cycle normally.

Cylinder Retract is only enabled until all are retracted, so there is less danger of burning out the solenoids.

Here is a modified ZIPped RSLogix version with the above changes, and a PDF for those who want to look at it.

leitmotif · Feb 23, 2008

Lancie1 said:
I know just the group that can come up with one. Is the Chief Bottle Washer for the old Smoke & Mirrors Corporation still hanging around?

Yeah he went to the engine room for a bucket of steam and relative bearing grease.

Dan Bentler

leitmotif · Feb 23, 2008

italian_virus said:
" Two requirements that are needed are

when the stop pushbutton is pressed all cylinders must stop in their respective positions (pretty simple) but when the start pushbutton is pressed all cylinders have to be retracted so the process can start over from the beginning. The thing is though how can I implement retracting all the cylinders on the start pushbutton without throwing off my binary sequence for the SQC and the SQO.

I have added two programs that I have done so far.
One has the stop button retracting all the cylinders though the bad thing to that is if the process stays off for a long period of time the solenoid valves stay on in their retracted positions, which in turn would cause them to heat up.

In the other program I tried to get the start button to retract all the cylinders but in doing so it throws my binary sequence off making the SQC not able to match up with my SQO.

You can order solenoid valves in either fail open or fail close with no power.
In stop mode the solenoids would be deenergized to prevent the coils from burning
and the valve portion of them would be open (closed) whichever you need.

Seems to me you need a
START where all cylinders start from position 0
PAUSE (and or HOLD ?) mode which will let you stop this wherever in the process and restart at the same point when interrupted (similar to opening lid on washing machine).
SINGLE CYCLE or REPEAT which will let you select
automatic CYCLE COMPLETE and stop it at end of a cycle OR repeat cycle
STOP which will stop it wherever and return to position 0

Dan Bentler

Lancie1 · Feb 24, 2008

You might need to add a couple of "Ready to Run" blocking contacts to your Block Mover program on Rungs 1 and 3, as shown.

italian_virus · Feb 26, 2008

Still a problem

Thanks Lancie1 for reviewing my plc program but I got another situation that has come up. I ran the program you gave me but the thing that happens is that after the first SQO retracts the cylinders the next SQO doesn't advance the first piston, which in turn makes the next step for the SQC unable to find its match (as shown in the picture I uploaded in the zip file). The only thing I can think of at this point is that the first SQO is still controlling the outputs preventing the second SQO from advancing the first piston. If that's the case then I’m back at square one with trying to find something to retract those cylinders on the start pushbutton.

Lancie1 · Feb 26, 2008

Well, after getting your program downloaded, I see that you did add the "Ready to Run" relay. I think now you need to add an XIO for "Ready to Run" to the right of the Safe Start contact on Rungs 001 and 002. This will prevent those rungs from trying to retract all cylinders (except for the first time).

Try this version.

I labeled the bits in I:6.2 to show which is Advanced and Retracted cylinder sensors. Check these for accuracy.

italian_virus · Feb 26, 2008

Thanks for all your help Lancie1 but I ended up solving my problem by cutting of the power to the first SQO by putting in normally closed contacts on the same rung and moving the resets of the first SQOs to the stop button (as shown in the zip file). I only have one quick question for you, for my program to communicate with the flex i/o I needed to configure my module's RIO scanner (G Data) to 1/2 rack. Why is it that the flex i/o can only communicate in 1/2 rack as compared to full rack or 1/4 rack. I included a picture of the flex i/o that the process is connected to.

Again thanks for all your help

Lancie1 · Feb 27, 2008

I am glad you solved the problem. I can't answer your question about the Flex I/O. I don't have the manual, but I am sure someone else here knows the answer.

Sequencer issue

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