GXDev: If I write some code, will it overwrite the PLC code?

[Mas01]

Hi, complete novice here. GXDeveloper:

I work in a test facility controlled by Q-series PLC.

I want to do some self-training on ladder logic.

If I write an example small piece of ladder logic and convert it and write it to the PLC CPU (as per the training material), will it overwrite the PLC software that's already on there that controls the rig?

Daft question, I know, but I want to make sure the rig doesn't grind to a halt because I wrote some small code. Obviously I will give my code/project a different name to the rig control software.

How can I run a software simulator to see what happens i.e. lamps going on/off, timers and counters incrementing etc.?

Thanks

 

[parky]

Yes it will if this is a new project, If you have the existing project or an upload from the PLC you can modify it and then download it but if you create a new project with just a bit of code then it will overwrite it.
Suggestions:
If you have a copy of the code that is in the PLC already then compare it with the PLC to make sure it is up to date, if there only a few small changes then upload it to your PC & save it as a new filename. If your backup (assume you have one) is up to date then save it as a new file, do your mods & download it this way you will still have a backup of the original. You can do on-line changes but only if the original is up to date with what is in the PLC. For an online change (just small changes like a couple of inserted rungs then change to edit mode, and do an on-line change), this will not stop the processor but add the extra code to the original. If this is a test rig then I think you need a bit of practice, do not do it on a live system without having a way back as your not experienced.

 

[Mas01]

Thanks for all of this, but I just don't understand. Surely there's a way for me to write a bit of code (just practice code) that's nothing to do with the rig control code, just so I can get some ladder logic writing experience.

 

[Mas01]

Edit: is there a free download of gxdeveloper I can install on my home PC for example?

 

[parky]

GXDeveloper is not free and I don't think there is a free version. If you have it at work and GXSimulator you can practice writing code and downloading to the simulator. If I remember correctly simulator comes bundled with GXDev.

 

[drbitboy]

Thanks for all of this, but I just don't understand. Surely there's a way for me to write a bit of code (just practice code) that's nothing to do with the rig control code, just so I can get some ladder logic writing experience.

I don't understand. If you ask The Google to search for [mitsubishi gxdeveloper], the first result takes you to a page that has a gx simulator link in the left panel, is that what you are looking for?


I don't know if Mitsi has trial downloads or anything like that, but if all you want is to poke around with ladder, then other manufacturers has low-cost or free entry-level ladder programming and PLC emulators; they will not use the GXDev instruction set or IDE, but the basic principles will be the same.

 

[parky]

GX Simulator is part of the package for GXDeveloper and is not free Ahem...
The simulator will not work on it's own. there are links that show GX for free but like if you search for RSL (AB) most of them are just ways of getting you to their website and there are no real links, yes you could chance on finding some (I will call them Dark Web) sites but most of them are files that will destroy your pc, you take the chance, I know one or two people who have been caught out.
Learning PLC programming on any platform is a good idea, but each one is different for uploading, downloading etc. and going on a live system you have no experience on could cause you to loose the program, a big no no if you do not have an up to date backup. Even though I'm an experienced programmer dealing with many different types, going to a PLC I have never worked on and making any change is not something I relish just in case I make a mistake, I have done many like this but there is something always in the back of your mind, thankfully never lost one yet.

 

[Mas01]

Thanks for the replies. I'm not trying to do anything dodgy. I created an account on MyMitsubishi and selected download for gxdeveloper. All seemed to go ok, got a zip file on my hard drive, unzipped and doubl-clicked on setup.exe....it seemed to work until I got to the point where I had to enter the product key...and there wasn't one supplied (surprise surprise) hence got to a dead end. LoL.
Anything really, as drbitboy said above, will do me, just so I can get some experience of writing small programs. Maybe an online simulator or freeware is what I'm after, just so I can mess around with it.

 

[parky]

I believe there are a number of free plc IDE's & simulators, if you register with Rockwell I believe you can download a free version of Logix500 + simulator + RSLinx communication software. The ladder is not the same but you will soon get used to it.
This site has one too to try

 

[PLCnovice61]

Mas01, Just to clarify about playing with the code at work. If you download ANYTHING to that plc running your test rig, you have altered the code that it runs on. If you write a small test code and download to that plc, the test rig is now running on the code you downloaded and if you don't have a copy of the original code to redownload back into, you just wrecked that test rig. The plc will only run on the code that is downloaded to it, so tread very carefully, or you won't be working there for very long and you may cause a machine to act dangerously and then you will really be in the poo. Do not touch that machine until you understand plc's, don't just having a play

 

[Mas01]

Mas01, Just to clarify about playing with the code at work. If you download ANYTHING to that plc running your test rig, you have altered the code that it runs on. If you write a small test code and download to that plc, the test rig is now running on the code you downloaded and if you don't have a copy of the original code to redownload back into, you just wrecked that test rig. The plc will only run on the code that is downloaded to it, so tread very carefully, or you won't be working there for very long and you may cause a machine to act dangerously and then you will really be in the poo. Do not touch that machine until you understand plc's, don't just having a play

Understood thanks. I thought that maybe the PLC was like a normal PC where you could write as many programs (eg in c++) as you liked as long as each had its own uniquely named executable .exe file.
PLCs clearly don't work like that it seems.

 

[drbitboy]

Understood thanks. I thought that maybe the PLC was like a normal PC where you could write as many programs (eg in c++) as you liked as long as each had its own uniquely named executable .exe file.
PLCs clearly don't work like that it seems.

Wow.


No, they do not.


Best to stay on a simulator not connected to anything for now, Baba Louie.

 

[parky]

Most PLC's have limited memory and if a full download was initiated it will put the plc in stop, clear the ram that holds the program and replace it with the new code. Siemens S5 was different, you could download a full program while the processor was in run. As S5 was split into blocks PB's FB's & DB's it downloaded into spare memory, removed the file table that pointed to the old location in ram and replaced it with the new block location. S5 was unique in it's day and on the early processors too many on-line changes would fill spare memory with blocks not being called and you had to do a compression to remove them, later this was done automatically, a bit like hard disks that do not remove files when you delete them they just remove the allocation but unlike the S5 plc eventually they will get overwritten. That is why in Mitsi on-line changes can only be a few hundred bytes as it has to shift the program to insert it.
So to re-iterate, if you have a copy of the source code but it is not up to date and you try to make a change it will not let you during on-line edits but will let you download it fully so destroying the old code. in essence, if your copy is different to the one in the plc it will be replaced, therefore always do a comparison with the PLC, If you do mods keep a previous version including uploading any data in the data memories in case you have to go back to the original. Version control is important.

 

[Mas01]

GXDeveloper is not free and I don't think there is a free version. If you have it at work and GXSimulator you can practice writing code and downloading to the simulator. If I remember correctly simulator comes bundled with GXDev.

I missed this reply, sorry.
I'll check if we've got GXsimulator.

 

[parky]

It may not be installed, if you can find the disk and run the auto run it should be one of the installs on the disk it should be the same serial number as GXDev.