PLC5 Debugging

[grnick50]

Dear All,

A customer wants me to do some troubleshooting on a PLC5-40 PLC.
RSlogix5 with RSLinx is available on-site. What I need to know is:

1. What is the battery replacement procedure? I guess I change the battery while the PLC is powered.

2. What cable do I need to use at which channel and with which RSLinx Driver? Is the cable something special I need to order from AB or can I make it on my own?

3. Do I need to bother with the memory card?

4. At what position does the switch need to be so that I can upload and monitor only?

Regards Nik

 

[Mickey]

See link to the manuals, which will answer most of your questions.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1785-rm001_-en-p.pdf

1. What is the battery replacement procedure? I guess I change the battery

while the PLC is powered.

Yes, if you do it without power you will lose the program.

2. What cable do I need to use at which channel and with which RSLinx Driver? Is the cable something special I need to order from AB or can I make it on my own?

A null-modem cable. The RS232 DF1 devices driver should work if the 25 pin serial port is configured for DF1 protocol ( thats the default configuration). Page G-7

3. Do I need to bother with the memory car

I would make sure it has the most resent program is in it. Update to make sure.

4. At what position does the switch need to be so that I can upload and monitor only?

"RUN" see page 1-9 of manual

 

[Operaghost]

When you say "Monitor Only" we have to be careful. As Mickey notes, the RUN position for the key will allow you to go online and upload. Placing the key in RUN will prevent downloading or clearing memory on the CPU. It will prevent modifications to the logic and it will also prevent you from writing to the EEPROM memory card as well. Those are all good things and what you asked for. But.....

It will NOT prevent changes to data. You will still be able to manipulate set points, change timer/counter presets and force I/O.

Now you may be aware of all that, but I just wanted to be sure you knew that using the term "monitor only" with the key switch would only apply to the logic.

If you truly needed a complete Monitor Only, you could either implement security or take a look at RSLadder5 which comes with RSLinx. It allows you to view the logic and the data, but the tool will not allow changes to the data.

OG

 

[grnick50]

Thanks for your replies. I dont mind being able to alter setpoints. All I would like is not to be able to alter the code and the EPROM data.

Is the 1747-CP3 cable ok if I use 9-pin to 25-pin adapter at the PLC side?

 

[Aabeck]

I use a standard 9 pin serial cable with a null modem adapter and a standard DB-9 female to DB-25 male adapter, if you have a null modem cable you wouldn't need the separate null modem adapter

 

[Mickey]

Is the 1747-CP3 cable ok if I use 9-pin to 25-pin adapter at the PLC side?

Yes

 

[jdbrandt]

Yes

..on the assumption that the DIP switches on the processor are, in fact, set for RS232. (RS4xx is an option...highly unusual to find it, but still, want to mention it)

 

[jdbrandt]

See link to the manuals, which will answer most of your questions.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1785-rm001_-en-p.pdf



Yes, if you do it without power you will lose the program.



A null-modem cable. The RS232 DF1 devices driver should work if the 25 pin serial port is configured for DF1 protocol ( thats the default configuration). Page G-7



I would make sure it has the most resent program is in it. Update to make sure.



"RUN" see page 1-9 of manual

Did everybody not see the EEPROM module in the front?
It would be nice to know what it is doing there...does it have the default program image? Is it set up for some special purpose?

 

[Lancie1]

Did everybody not see the EEPROM module in the front?

Yes, and many times when a customer wants "troubleshooting", it turns out that the PLC5 has lost its program due to battery failure or electrical line surge. If so, the EEPROM may contain the only working copy of the customer program. Or not (the EEPROM could have an old obsolete program that has not been updated for the last 10 revisions).

 

[grnick50]

I built the cable and I succesfully did the troubleshooting I was asked for and the replacement of the batteries. I also did an upload of 7 out of 8 PLC5 PLCs.
The problem with one of them is that RSlinx could not see it.
Please see attached a screenshot of the RSLinx. When I hit the autoconfigure button RSlinx seems to get stuck for a while at the point where it says "Testing Mode: BCC".
Do you have any Ideas of what maybe wrong?

Regarding the content of the EPROM, is it possible to run a sort of compare command to check if it has the same program as the processor? How do I read - write on the EPROM? Do I need a Prommer as it is required for the Simatic S5?

If I need to remove the CPU from the rack, How do I do it? Given that there is a fresh battery on the CPU, is there a loss of data risk when the CPU is out of the Rack?

Regards Nik.

 

[Mickey]

The serial port on a PLC5 can be set to RS232 or RS422(rare) by dip switches on the processor.
The port can be set for DF1 protocol ( default) or ASCII. Is/was there anything connected to the port?

You might try configuring RSLINX manually for the default configuration of the PLC5.
Baud rate: 2400
Stop Bits: 1
Parity: None
Error Checking: BCC
Ptotocol: Full Duplex

If I need to remove the CPU from the rack, How do I do it? Given that there is a fresh battery on the CPU, is there a loss of data risk when the CPU is out of the Rack?

Power down flip up the small lever at the top, disconnect all wiring and pull it out.

With a good battery you will not lose the program. It will hold it for years.

See PDF for how to burn the EEPROM

 

[grnick50]

Nothing is/was connected to the PLC port. I already checked the manual and I saw hoe the DIP switches need to be set for RS232 comms.
As I am not on site at the moment, could you please tell me if you know if I need to remove the CPU from the Rack to change the DIP switches?
To change the DIP switches I guess I need to powerdown the CPU?


Regards

 

[Ron Beaufort]

before you pull the processor – let's go back to your first post for just a second ...

RSlogix5 with RSLinx is available on-site.

I'd be willing to bet (pocket change only) that somewhere at that plant is a computer running RSLogix 5 which is already connected to the Data Highway Plus network (blue hose) ... IF so (big IF) that's correct, then you can PROBABLY access the PLC-5 that's giving you problems over the DH+ network ...

in a perfect world, just pulling the processor out to check the switches wouldn't be a big deal ... but ... if that system has been "plugged together" for a long time – well, sometimes when you pull it apart and then put it back together again, the backplane connections don't always make good contact ...

if I were responsible for pulling the processor – I'd be sure to have a small can of quality contact cleaner handy ... WD-40 makes a good cleaner – but it can also dissolve some types of insulation, etc. ... personally I don't use WD-40 for this type of operation ...

some folks recommend the use of a "Pink Pearl" eraser to polish up the contacts on the module/processor – but Allen-Bradley says that operation removes a lot of the gold plating on the connections ... plus – you can't get the eraser back into the slots that the cards plug into – so you're only able to clean one-half of the connections that way ... (Knowledgebase article 17672 has some comments on this subject) ...

another common "trick" is to slide the processor/module in-and-out-and-in-and-out several times ... this sort of "wipes" the connections against each other and will often get you back in operation ...

basic idea:

if your system is in a relatively clean environment – and your battery is good - then pulling the processor out and putting it back in shouldn't be a big deal ... but ... sometimes things don't work out the way we expect them to ... personally I'd check to see if there's already a DH+ connection available that could reach that particular processor ...

good luck with your project ...