How do I fix this?

[iwire]

This is partly why the NEC now requires nameplates on 'control panels'.

For sure.

I would check with a local AB automation distributor. They probably have a customer list that includes a 'system integrator' that could download and print the program for you. Heck, they might even have an in house tech support person.

I will keep this is mind, thanks.

 

[iwire]

999 time out of 1000 if the PLC is up and running for years and years you can fix the problem without going online with the processor. Its some physical I/O that has gone bad.

I agree, I am not looking to 'fix' the programing.

Of course it makes it much easier to trouble shoot if you can see the logic.

No one on site knows how the machine is supposed to work so without seeing the programing I am in a tough spot.

Thanks.

 

[iwire]

161222-1234 EST

iwire:

Call the photo-detector location where the original detector failed Photo-1, and the next location after it Photo-2.

After the new photo-detector was installed at Photo-1 it worked. I assume this means that the input LED at the PLC for this detector also worked as expected in a direct on-off respect, and with no time delays.

Correct, when I replaced photo-1 the LEDs on it and the input at the PLC changed state instantly when blocked and unblocked with my hand.

Then a bin was moved on the conveyor and when it reached Photo-2 position something did not work. What did not work?

As I did explain above now with photo1 replaced when a bin breaks the beam of photo2 all motors stop and cannot be restated until the bin is removed from the beam.

Previous to my arrival and replacement of photo1 the machine was delivering bins nonstop and breaking the beam of photo2 had no effect on the machine.

At this time does changing the state of Photo-1 detector produce a corresponding expected change in the Photo-1 input at the PLC?

I do not know.

Also at this time and before did the LED at the PLC for Photo-2 work as expected?

Photo 2 changed state but had no effect on the machine previous to the replacement of photo1

.[/QUOTE]

 

[iwire]

Got a make and model on the photo eye? Not sure why it might matter, but you never know.

Allen Bradley 42GRU-90002-QD

One possible thing to look for is that sometimes in systems like this; a photo eye not working gets the entire sequencing out of whack and it can't recover on it's own. SMART programmers will put in a "Reset" or "Homing" function, often initiated by a simple switch and in many cases, that switch is NOT on the door to avoid having operators use it incorrectly. It may be a switch or button INSIDE of the panel.

Could be but very small and simply control cabinet and I do not see one.

Thanks

 

[iwire]

Call your local Allen-Bradley distributor. They will usually have an A-B teck-rep on staff. Ours is very helpful. I don't recall seeing which A-B PLC is involved. Is it a PLC5, SLC500 or micro-logix, Control logix or what? A-B (Rockwell Automation) software licensing IS pricy, but if it's a PLC5, you can usually find a software download for RSLogix5 that gives a 7 day activation. The software download is free, it's the license thats expensive!

I will keep this in mind but pretty much not my call to make.

I tried to pass on this job but I am stuck with it.

Thanks

 

[iwire]

Another question I might ask is about said abandoned limit switch. Was that removed to make the machine functional after the PE failed? With the PE replaced, is it possibly waiting for something to "make" that limit switch?

Its all questions because there is no documentation, there no one that knows how it is supposed to function.

It is delivering bins today as it has been ... with broken photo eyes and limit switches. My only concern is making the safeties work again.

 

[iwire]

It is a ML1000. I have several used ones on the shelf.
Software does you no good if they protected it. I've never worried about doing that but some do.

I could send you an old laptop with software and cable if you're hurting, but the suggestion about the local AB distributor is a good one. They will know who.

What a kind suggestion, really thank you but if it comes to that this customer can afford to pay for / buy what they need.


But thank you again. Bob

 

[iwire]

I work in a paper mill and we use these same sensors for sheet detection. If they both seem to work correctly, which it sounds like they do, verify the "light/dark" setting. Or simply change it from one to the other and see if it fixes it. The Photo eye will still function correctly even if it is on the wrong setting but the PLC won't recognize it. I agree with others that unless the PLC logic has been flawed from the start, it is extremely unlikely your problem.

I missed that setting when I installed it. I am going back Tuesday and will be checking that.

 

[mike_kilroy]

Silicon Labs makes the bridge (driver) to make usb to serial work and it's free. I don't understand how there can be a counterfeit of something that's free. Cables are cheap. The hardest part is checking what port picked it up in Device Manager, and that takes all of 10 seconds.

There are a lot of different chip and driver mfgrs... Google "counterfeit usb serial adapters" if you wish to learn more about this big counterfeit problem. Some examples:

http://www.epanorama.net/newepa/2014/10/23/on-counterfeit-usb-serial-chips/

http://www.eevblog.com/forum/review...d-with-prolific-(pl2303)-usb-serial-adapters/

http://www.portlandiacloudservices.com/usb-to-rs232-serial-port-adapters-clones-counterfeits/

 

[iwire]

View attachment 16350Having the actual file vs upload from PLC.View attachment 16351
These are pretty small but having the file would give you names and notes of each I/O vs just the logic the PLC uses.
It might help but its still a PIA.

I do not understand, my PLC work is pretty limited.

 

[iwire]

At a guess, I'm inclined to think it isn't a PLC problem.

Again I do not think it is the PLC, but without manuals for the equipment I do not know how the safety / fault systems are intended to operate.

 

[iwire]

Go buy a cheap laptop at WalMart. Spend whatever money you need to. Do the job and leave the laptop with the manager at the store. He will now have what is necessary to maintain his equipment. Do it all at his expense.

I do not know what to say to this one. Have you read along?

This is a supermarket, no one there is qualified to be using a lap top with the PLC.

 

[iwire]

There are a 'boat load' of wires between the PLC and the field terminal strip, however it looks like there are only a handfull of field devices.

I noticed that as well.

My guess is that the PLC is 'out of sequence' with the real world. For some reason, these are often hard to re-establish if you do not know the secret handshake.
Heaven forbid, if the original program designer expected this to be job security where they had to be called in for servicing. Proprietary systems are definitely a bad idea when the 'proprietor' is no longer in business.
Any PLC ladder diagram is better than nothing.

That may well be the case.

 

[iwire]

161223-1338 EST

iwire:

I don't want to go back thru the thread and look at details.

This is what I think I remember:

1. You have a customer with a conveyor system that failed.

]

They noticed the LEDs on photo1 were no longer illuminated. The machine never stopped delivering bins.

3. You observed that Photo-1 appeared to not work, and replaced with an identical unit, and adjusted the sensitivity. Changing the state of Photo-1 produced a change in state of the input indicator at the PLC.

Yes

Can you provide any information on what the this conveyor is supposed to do?

It delivers bins of groceries from the store down one level to a parking garage. That is all it does.

It has three parts, a standard horizontal conveyor on each level and vertical conveyor between them like this one. A very simple machine, a total of three motors and maybe eight safety switches.

Only for smaller bins.

 

[iwire]

Silly question... if it is out of sequence, would powering it down and back up reset it?

This has been done and no change.

 

[mgookin]

I do not know what to say to this one. Have you read along?

This is a supermarket, no one there is qualified to be using a lap top with the PLC.

It will always be there for you or whoever is working on the system. You could lock it in a cabinet near the conveyor and put the key inside the panel.

 

[iwire]

Dumb question, but how do you know that getting it to work will equate to getting it to work safely?

:lol:

Its working now, it never stopped delivering bins.

However if the employees do load the bins into cars fast enough I see nothing that is going to stop the machine from trying to push more out. It will get ugly fast. The bins will get eaten by the vertical conveyor.


My entire purpose is to restore all the factory safety switches to operational.

 

[iwire]

That particular PLC should have nothing to do with machine safety. It is not a safety rated PLC. The machine safety system should be controlled by another source in this instance.

You never want e-stops, safety limits, light curtains, etc going to a regular PLC for safety purposes. I'll often times run a secondary control circuit on an extra set of contacts from those devices to inputs back at the plc just for monitoring and alarms, but the primary control circuit through them is what actually shuts the machine down.

No true, modern safety relays on this old equipment. The E-stops are signals to the PLC in the picture.

 

[Ultrafault]

If you check every input device and they are all functioning and in propper alignment it can't be any thing other than the plc. Check your input devices and you are halfway done.

 

[iwire]

So get a map of the PLC inputs and outputs. Figure out what input should create what output and use a meter to read the signal.

Where am I getting this map?

:?


Are you suggesting making dozens of input combinations and noting any output changes?

With all the internal trickery that can be done in the programing I do not see that as realistic.