PLC novice in need of advice

[Nathan1978]

Hi everyone. I am an absolute novice when it comes to PLC's and am in need of some expert advice and i'm not sure where to start asking questions so i thought here might be the best place to start so i'll try to give the best description of symptoms.

I recently powered up a stone masonry machine that runs a Siemens Simatic S5 115U CPU 941. The machine hasn't had power in about 3 years.

Upon power up the stone masonry machine would not respond to any of the commands through the operating console. An electrician has confirmed the PLC is in "STOP" mode and upon investigation we have discovered the Backup battery is dead (removed, tested and reinstalled) while the machine was powered and the low battery light is indicating on the PLC. I purchased the machine as is and have no back up of the program on the PLC. The machine to the best of my knowledge (while similar units were constructed) was one of a kind. I also noted lights were signalling on the input side of the PLC in response to operating console functions- i'm assuming it was reading my input commands, though while in STOP mode would not execute them.

I am very apprehensive about playing with any components (like the PLC) that could render my machine useless.

I have since learned the machine has an "EPROM". Does this mean my program is still there and i simply need to replace the battery prior to powering up the machine again? Can anyone suggest how i can get my stone masonry machine running again? Any advice would be very much appreciated. Attached is a photo of the PLC while powered if that helps. Thankyou again.

 

[KalleOlsen]

Hi, and welcome to the forum.

You might be in trouble, but let's try some first aid.

Push and keep the lower switch to OR and
with the upper do RN - ST - RN - ST.
Release the lower switch.
Pray to the local gods and do a ST - RN.

Any luck?

Kalle

 

[TurpoUrpo]

I love the orange.

But yeah, you my friend are in need of gods or some other higher powers.

 

[Nathan1978]

Thanks Kalle and thanks for your patience in regards to my ignorance of all things PLC! I will try that in two days when i can replace the battery. Now just to clarify, the whole machine was running when dismantled and is currently unpowered and will only be powered when in use (as i'm running all power through a diesel generator).
From your post i gather you recommend (while powered) that i hold down the lower switch on the CPU side and toggle between Run and Stop twice then release the switch and then finally switch from stop to run?

 

[Nathan1978]

Thanks TurpoUrpo. What is the purpose of the EPROM? My understanding was that it was something of a memory card or cartridge to store the programming details specific to the machine's functions and only erasable by UV light? Does the lack of power also remove these programs from the EPROM? I am hopeful divine intervention will not be my only salvation and any constructive advice is most welcomed.

 

[KalleOlsen]

Thanks TurpoUrpo. What is the purpose of the EPROM? My understanding was that it was something of a memory card or cartridge to store the programming details specific to the machine's functions and only erasable by UV light? Does the lack of power also remove these programs from the EPROM? I am hopeful divine intervention will not be my only salvation and any constructive advice is most welcomed.

You are right about the EPROM. But it doesn't necessarily contain the complete program - let's hope it does. The moves I suggested will delete any trash in the RAM and do a complete restart. If there is any code in there generating DBs, the RAM will now be empty and provide space for that.

Btw, can you tell the MLFB number of the neighbour card of the CPU? I cannot read it from the picture even with my welding goggles on.

Kalle

 

[ktmtragic]

Do this:
Remove the battery.
Power down the system.
Hold down the Run stop copy switch below the Eprom
Power up system while holding switch down
When lights are stable flick into Run
Install battery and you should be good to go

 

[Nathan1978]

Thanks Kalle and Ktmtragic. Kalle i think the number you were enquiring is 6ES5000-1AA1. On a further note I am relatively sure the machine (while it was running previously) would have been switched off regularly as it has a rather loud and noisey cooling fan that operates inside the control enlcosure of the masonry machine which i highly doubt would have been left to run around the clock. My very limited understanding leads me to believe the CPU system and device programming would be on the EPROM entirely (fingers crossed!)although my inner sceptic also wonders why still utilise a battery...

I'm not exactly sure what the run stop copy switch is Ktmtragic. Is that the same as RN ST switch immediately below the EPROM on the CPU? Or is it the NR RE OR switch towards the bottom of the CPU? Also both methods are quite simple but is your method any safer than what was suggested previously? I can kinda comprehend Kalle's suggestion and dump the ram, reset and reboot. Is you r method roughly speaking achieve the same?

Btw. I cannot thank you guys enough. I am truly out of my depth here and your input is appreciated.

 

[ktmtragic]

Sorry the procedure I mentioned was for a 90U. Try holding down the bottom switch OR on power up with the unit in stop, and then put the top switch into run after about 10 seconds. Here is a link to the switches on the CPU.
https://www.dropbox.com/s/pdan22pju47s7cv/115%20CPU.png. See explanation lower rt
If it is too small click in the bottom right corner and click view original.
Does the bottom switch return to center or is it 3 selectable positions? It is 20 years since I played with these beauties. If I recall holding the button down on OR is overall reset. Don't worry if the Eprom is ok you will lose nothing. If I recall correctly by holding down the OR button on power up it bypasses 2 starting blocks OB1 and OB2. The Eprom stores all of the factory settings and how the program works. Like a sim in your phone stores network info and carrier settings. The battery powers volatile memory and stores all user info used in a process program ie cut block 300x300x40 as sizes and parameters change this info changes constantly. The down side is no battery no remember. Hope this helps you understand a bit better.

 

[Nathan1978]

Thanks ktmmagic. What you are saying regards the machines setup and the way the PLC stores various sizes and parameters on its RAM that are interchangebale makes perfect sense as it does have an automated pseudo cnc type function with a numeric keypad to enter process profiles and distances on the work piece. I guess for its age (commissioned in 1986) it was quite cutting edge in the stone sawing business! No pun intended.

To answer your question the bottom switch does have 3 selectable positions. The top two positions on the switch will hold position and the OR switch position at the bottom must be held down.

Just to clarify to a newbie like myself the technique you described is to;

a) power up the machine in STOP whilst holding the bottom switch in the OR position then whilst doing so,
b) after 10 seconds switching the top switch to RUN and then releasing the OR switch

or should i;

a)power up the machine in STOP whilst holding the bottom switch in the OR position then,
b) after 10 seconds of the OR switch being depressed, release the OR switch and change the top switch to RUN

As you mentioned hopefully the EPROM is still ok. Ideally i would like to connect with the PLC and copy the EPROM programming to at least have a back up and in readiness to transfer to an S7 PLC at some later stage, which correct me if i'm wrong is possible.


BTW. Thankyou so much again, your assistance has been invaluable for someone like myself trying to set up a small hobby. I know its not much but be sure to let me know what you drink and i'd be more than happy to send you a bottle or carton! Same to you kalleolsen!

 

[ktmtragic]

Ok My experience is mainly with the 90-95U.
The Eproms are pretty bullet proof so I don't think it will be a problem. Power down pull the Eprom out power up wait 30 seconds.Power down install Eprom .
Hold down OR switch on power up. With top switch in stop. Led's will flicker when all is steady release OR switch. Now switch to run.In my opinion Siemens were the ducks guts back then but definitely not now. The S5 to S7 conversion is not backwards compatible so you will need new HARDWARE and SOFTWARE. (This is where Siemens lost the plot)in brackets got greedy and we all, to use the Aussie vernacular ****ed off. Please post back what happens
Good luck

 

[KalleOlsen]

Hi!

Here is a link to the manual:
http://plc.scetc.net/down/zz/plc/siemens1/SIMATIC.S5－115U.pdf

The startup and overall reset is described on page 49 and 116.

I've overlooked one thing that you could try after the overall reset and before startup. You might find forever happiness if you switch the lower one from RE to NR (remanent to not remanent) before you try to start.

If the power/battery is out, a restart with the switch in RE is prevented cause the remanence is not possible without a voltage source. But NR is allowed because all markers, timers and counters are reset to zero - a defined state.


I hope all this info about how to manipulate those two poor switches hasn't confused you too much

.

Kalle

 

[Nathan1978]

Hey guys,

Quick update. Purchased a new battery today. Mixed results as follows.

Step 1/ I powered up the machine and while running installed the new battery.
Step2/ While powered i switched the machine into RUN. PLC remained in STOP.
Step3/ Attempted ktmtragics solution. PLC remained in STOP
Step 4/ Attempted overall reset according to manual. PLC remained in STOP
Step 5/ Attempted overall reset according to kalle's first suggestion. PLC went into RUN!!

But....... just when i finished celebrating and began to attempt to input into controller...Nothing. Not a thing. I did notice some of the input relays light up however. And i did notice on the input cards that even with no input into the console there were two lights that were remaining lit.

Now... I have checked on the 30 year old and very yellowed schematic i have obtained that input E7.3 and E8.7 are lit up and indicate "control voltage off" and "emergency stop" respectively. I have no idea what control voltage off input might be but i'm guessing it may be tied to the emergency stop? i am also guessing that there may be a damaged emergency stop button (there are at least 3 that i'm aware of) may be stuck on? Does this sound like a possible scenario to you guys that might prevent the machine from roaring into life and allowing the PLC to output my input commands?

 

[ktmtragic]

Great to see you are in run.
Does it show whether the inputs should be open or closed on the schematic? A control voltage failure or E stop will stop it dead and they may be tied to the same thing. Can you post the schematic?
cheers

 

[Nathan1978]

Here they are ktmtragic. They are of the input side. I hope you can see them clearly enough.