Opinion/advice for replacing ageing PLC

I hope this post doesn't start a deluge of opinions and arguments...
I have a Toshiba EX40Plus and EX20 Expansion.
Is there a modern counterpart that will drop straight into it's place please?
Thanks.

Not probably drop directly as connectors may be different, however, the Mitsubishi FX range is probably the nearest, in fact you may even find pin outs almost the same. They do not tend to have block extensions as standard rather 16 way input/output cards wired from bottom, however according to MEU they do FX2N powered extension blocks these are similar to the ones you want to replace (FX2N was superseded by FX3), but it appears these extension blocks are still in production & have not been renamed FX3.

Thanks for the suggestion. The connectors are the stripped wire ends, but if they could connect to a new PLC in roughly the same places it would be helpful. I just need an engineer to come and fit it all now....

It's not just a case of fitting, it needs programming & you will need one of the following: a copy of the original program (well at least an upload) assuming it's not been protected, a disk or copy of the documented program either on disk or printout, In none of these are available then either if the PLC is still powering up then copy of the software to upload the code or the alternative is to re-write based on knowledge of the process but this would be costly.

I have 17 A4 pages of printout of the program that I found in the cabinet. I assume it hasn't changed... I scanned them so I have a jpg backup. There's no PROM with the PLC and I think the Programmer interface is faulty. I've put an oscilloscope and a multimeter on the contacts and I get +5v on pins 1 - 4, and 0v on pins 5 - 8. Nothing else, whether during power-up, or running.
I have all the software for programming it, with an RS232/RS422 converter, on a specially built XP laptop and it all appears to work, just not the EX40.

Another factor is what HMI is connected, if any. Is it possible to reprogram, or does it need to be replaced as well? Depends on the brand and model.

There's no HMI as such, I don't think. I've attached a photo of the Control Panel for your examination.
The two displays just show temperature in diffent parts of the Drier. They're old red 7 segment l.e.d. displays.

If you have a printout that is the current version of the program, then you could replace it with pretty much whatever you want. One model I can recommend is S7-1200 from Siemens. A 17-page program is not so huge to manually enter again.... I did a 500-page manual entry before.

You would need to pay very close attention where the existing wires are, in order to match them to the new replacement PLC. If you don't have a good wiring diagram, make sure the existing wire labels/numbers are clear (or make your own labels with white stickers), and take photos, then you have a good backup of the existing wiring before you start changing it over.

Maybe this link will help:

http://plc.gtprototype.com/toshiba_ex100/manuals/EX20_40%20Plus%20Manual_506.pdf

From this manual, you have 24 digital inputs and 16 digital outputs on the EX40plus CPU and 12 digital inputs and 8 digital outputs on the EX20exp, for a total of 36 DI and 24 DQ. Also, it looks like all the inputs are at the top of the existing modules, and all the outputs are at the bottom. The S7-1200 CPUs are similar with inputs at the top and outputs at the bottom, as well as the S7-1200 DI/DQ combo expansion modules. This is the S7-1200 system manual:

https://cache.industry.siemens.com/dl/files/465/36932465/att_106119/v1/s71200_system_manual_en-US_en-US.pdf

I still recommend the Mitsubishi, if you are not familiar with PLC's the FX range has inputs & outputs that are the same i.e. X for inputs Y for outputs in octal format (X0-X7 then X10 -X17 etc.), the only real difference is Mitsi has M for internal relays where the original uses R, timers are generally the same. The I/O terminals are almost identical except the outputs are in groups of 4 i.e. a common supply for each group of 4 where the Tosh has individual feeds I believe (you need to check that for each group i.e. Y0-Y3 has the same supply and so on).
One other point, you mentioned the problem is one output not working, generally if the LED for that output is on but no feed through relay then it could be assumed that the output relay is faulty, however if the output LED is not lit then it is more common that the logic that controls that output may not be energizing the relay. In that case there may be a signal not true within the logic so it could be it's not the PLC (other possibility is that an input is faulty have had this before). If the output relay is the culprit then it is possible to replace these with care, however, I assume because of the age the battery backup may not be very good, It is possible this is battery less memory but unlikely as these are generally later additions.
Dismantling the PLC to replace the relay may mean disconnecting the battery backup then the program may be lost. If Eprom then no problem.
Depending on the output that has failed it may be possible to tag it onto another output that contains the same logic if it does, then this will get you out of a mess, however, this system has I presume gas burners so be aware of the control i.e. Purge, Interlocks etc. that are needed for safe operation.

Thanks for the prompt and helpful responses again all.
@sigmadelta:
I already have the EX40 Manual but thanks very much for the Siemens equipment manual, and recommendation.
I don't have any wiring diagram, but I do have a labeller and plenty of time, so if it comes to it i'll definitely use both whilst I create it ;-)


@parky:
As my major unfamiliarity is the programming, (although I have done my share of perl, bash, B.A.S.I.C, x86 assembler, C++, DOS batch files), anything that makes the conversion easier is attractive. However if hardware replacement becomes the goal then I'll ask a professional to take over, and bow out of the fix. If I could talk to the EX40 then I could pull off the program and check that it's correct, (I'm willing to learn it to try to fix this).

The misbehaving output is actually switching on when it shouldn't, so the hardware is working. I've disconnected the output wiring and the equipment doesn't come on, proving the cause back into the controller, and not an external wiring short. If the program tuns out to be correct I'm willing to try to change the output, and program to suit, to try to fix this.


If only I could get the comms working.....

If you like, post the program (it would be better to convert the jpg pictures to pdf) and tell us which output is the problem. Outputs can misbehave because of an input device(s).

EX40Plus has relay outputs, you could try to access the PCB to replace the defective relays. I used to do that with Siemens S5-101U PLCs wich is very similar to this museum piece.
I am assuming you conclude the output is defctive because the LED goes on, but the output does not change.

Of course, doing anything to this dinosaur is only to buy time to do a proper upgrade to something modern. Any small PLC will do. S7-1200 could be a nice fit. 17 pages of simple ladder logic is trivial to recreate.

Which output is it Y xx I could look at the printout and see if it's something in the program, I have looked at the listings & it's obvious that the printout is probably the original, who ever commissioned the plant has made a few mods (as per biro on the drawings), however, there could be others that they have not modified the printout and some seem to be a little confusing.
Here is the hardware manual for the FX3G PLC Looking at the I/O count you could get away with a FX3G-60xx The manual gives you drawings & Terminal connections there are DC/AC transistor output types etc.
Assume the original is 110-240v Power with 24v DC inputs & relay outputs then the FX3G-60MR/ES would suit without an extra I/O module.

https://docs-emea.rs-online.com/webdocs/0e62/0900766b80e62898.pdf

I would also replace the arcaic operator panel for a touch screen.
You then can have real alarms with detailed alarm descriptions, logging of alarms, trendcurves, ease of making changes to both PLC and HMI without the need to shut down, possibility for remote support, etc.

A reasonably inexpensive but still reasonably good touch screen costs approx 500 €.

fixit9660,

I may have misread some of the posts, but just because you have a printed copy of the program, doesn't mean it is the current version with program changes, timers, counters, real numbers.....
the master copy is the plc program itself.
what I would do is this.
go to the machine and watch it run (for 30 minutes or more, each station).
watch the operator and all his actions.
start writing down what you see on paper and in order.
ask lots of questions, the operator and maintenance is a valuable source of info.
then when you are comfortable with what you wrote down, look at the program and see if it matches what you see.

I did an upgrade several years ago and was told the printout they gave me was current. I was fortunate enough the have the software on a very old pc we kept and downloaded the program. Good thing I did. lots of changes.

james