Help Resetting PLC Code

[rob.adam.plc]

WE are Electrical Tech. Eng. Students who have created a pneumatic robotic arm for our Tech Thesis Program. THe arm is controlled by an Allen Bradley Micro Logix 1000 Unit, (RS logix 500 program).
WE have ladder logic which controls the arm as desired, but unfortunatly we cannot get the program to repeat. WE have tried various methods such as resetting the counters/timers, adding a contact before the code to open and reclose, but still no success repeating code. (WE have various limit switches for the I/P's and Solenoids for the O/P's)

If anyone could help us getting this code to repeat after it has completed it would be EXTREMLY appreciated as if it does not work we will be marked uncomplete on the project (even though the program works correctly on one run and manual override works flawlessly).

Rob & Adam

 

[Oakley]

If I were the instructor and knew this, it would definitely get an incomplete.

The key is repeatable code - for the robotic arm to do a task and repeat it.

What happens when you complete the action? Does the robotic arm return to home? Think through your flow chart ... you did a flow chart and control philosophy prior to writing any code - right?

 

[rob.adam.plc]

Yes the arm does return to it's original position.
Also, just to add, we have formal trainin on Siemens only, This is our first time using A-B.

We know the program must repeat. That is a no brainer, but the problem is we don't know HOW to get it to repeat.

Thanks for your input though/.

 

[rsdoran]

Use the report option in RSLogix and print a report of your ladder into a pdf file. You can obtain a free pdf program at http://www.pdf995.com/Then you can post the pdf file here and anyone can look at it and offer assistance.

 

[Ken Moore]

What starts the process?
You will need an "or" condition added to your existing start.

If start_PB OR (last step completed AND system_ready) then start.

 

[rdrast]

I am firstly curious about what you mean by 'Repeating' the code. If this is programmed in Ladder, than your code is 'Repeated' many times every second.

I'm sure you mean, 'Repeating your desired sequence'.

Trying to randomly reset things is, well, silly. YOU programmed the system, YOU know the initial conditions required to start the sequence, and YOU know the terminating conditions of the sequence.

Does it work when you first power it up? And then never again? What flags, timers, etc have you changed? What was their initial condition?

Create a subroutine (I'm shocked you don't already have one, how do you HOME the system?)... Call it 'INITIALIZE'. Use it on the first scan of the program, and also when the program is complete to resequence your arm.

I guess school's back in session.

 

[rsdoran]

I am not sure about some statements. A plc does not repeat, it scans (or reads, the code many times per second. The "process" the code controls may or may not repeat depending on how it is programmed.

I am not sure about the need for a subroutine in a plc as small as an ML1000.

Post a copy of the code by either zipping it or creating a pdf as I mentioned above and someone will help.

 

[adamtuffin]

got it workin

hey, we got our process to reset, i guess we will get our "complete" mark after all.

we used the "RES" option for timers and counters, implemented them with another counter and timer, we needed a timer to delay the reset (.25 sec). process works fine.

thanks for the feedback. peace out

TooGood