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Posts from — December 2011

Free PLC Simulators

I recently decided to see what kind of free PLC simulators and integrated development environments (IDE) I could find that run on Windows.  A free IDE+simulator is great for teaching; for example, I can give examples that any of my readers can try out, but if I use a real PLC, I’ll be using what I have (Panasonic), which probably isn’t what most of my readers have.

Here is what I found:

  • Tri-PLC’s i-TRiLOGI free development environment supports both ladder logic and their version of BASIC and includes a simulator.  Tri-PLC also sells low cost PLCs.
  • Infoteam’s OpenPCS free development environment supports all the IEC61131 languages (including ladder and structured text) and includes a free PC-based simulator.  Infoteam’s business model is similar to CoDeSys:  customizing and charging money for the OpenPCS runtime.  (CoDeSys also has a simulator, but their free download is time-limited to a maximum 1 hour continuous run time.)
  • EasyPLC is basically a soft-PLC with a HMI builder and is free in demo mode (simulation only).  It’s worth a look: for example, its simulation mode includes 3D.  The commercial license is affordable, starting at 50 Euros).
  • I vaguely recall rumors of being able to use an Allen-Bradley simulator for free, but couldn’t find anything when I searched (besides,  I don’t think the development software would be free….) Note 3/15/2012: see next paragraph for A-B link
  • Via MrPLC, I found a link for Allen Bradley MicroLogix 1000/1100 free starter software and RSLogic Emulate 500 simulator.  I haven’t tried this combo out, and I don’t know the limitations, but in theory you should be able to learn some A-B programming for free.
    • Update 11/25/2014: this link no longer works, although the download might still exist elsewhere.p 
  • Automation Direct’s Do-more Designer is a free download and includes a simulator.  It appears to only support ladder logic (no Structured Text).  It can drive I/O (such as Ethernet I/O) from a computer, so it will only run continuously for about an hour.  (Added 7/17/2013)
  • Codesys has CODESYS Control for Raspberry Pi SL.  The free version is limited to 2 hours continuous run-time; a license for 35 Euros removes that restriction, but it’s still restricted for training and testing use only.  Capabilities include EtherCAT master, Modbus TCP Master/Slave, Ethernet/IP scanner, Web Visu, and SoftMotion CNC.  It supports the Raspberry PiFace digital I/O module.  It’s not realtime; expected jitter is 50 to 400 μs.  (Added 11/4/2014)
    • If you’re interested in learning IEC61131 PLC programming, playing with EtherCAT drives or I/O, etc, it’s an interesting product, since you can get started with real hardware for $65-$120 (RPi+PiFace for ~$65, Codesys SL license ~$50).
    • has an online PLC simulator (signup required).
    • And, if you have sophisticated safety requirements, at least three safety PLCs have free simulators.  However, these three are all based on block diagram (like a Siemens’ Logo!), not ladder logic, and are definitely not usable as a standard PLC.
      • Leuze’s software is on this page.  We are currently using the MSI-202, and before we bought it, I successfully used the simulator.  However, it’s not instantly intuitive.  As far as I can tell, the Phoenix PSR-TRIFASE is the same controller, and its software is also free.
      • The Sick Flexi-Soft Designer software is here.  The Flexi-Soft is also sold by Mitsubishi (it is a joint product).  I evaluated this software, too, but we decided the Leuze was a slightly better fit.
      • The Banner XS26 software downloads are available here; I haven’t used it but saw it at Semicon West 2015.
    • Although it’s not free, I should give a mention to Siemens’ Logo! Softcomfort, since its simulator is very easy to use – and very useful, since none of the Logo! models I have used provide any on-line debugging information.  I believe Siemens do offer a free trial.

I choose to download and try out OpenPCS because I really like having support for all the IEC61131 programming languages.  I haven’t used OpenPCS enough to be able to discuss it intelligently, but hopefully I’ll be able to write more in a month or two.

If you really want to learn PLCs, then at some point I think you have to buy a real PLC and connect it to real sensors and outputs.  Simulating stuff just isn’t the same.  Real PLC’s can be quite affordable; many manufacturers (including IDEC and Siemens) sell complete kits (PLC and software, plus sometimes a HMI) for $250-$400, Tri-PLC and the Automation Direct Click! series are <$150 and have free software, Panasonic FPWinPro 6 Basic is free (but code size limited), etc.

Beyond PLC’s there are some interesting options.  For example in the PAC world Opto 22 has a free IDE and control simulator, but you need Opto 22 I/O since there’s no I/O simulation.  In the robotic world, Denso Robotics has a free 3 month trial of WinCaps III which includes 3D robot simulation with no controller required.

Back in the PLC world, I’ve finished reading Cascading Logic; it’s a good book, and I hope to get a review up fairly soon.

December 5, 2011   5 Comments

Notes On Fixing Rubber Dome Keyboards

I recently fixed some older compact computer keyboards: two Unicomp Mighty Mouse M keyboards with separate numeric keypads and a IBM/Lexmark SpaceSaver.  One keyboard had some keys that didn’t work at all, and the others had a couple that didn’t respond reliably.

All three keyboards are pretty similar.  They use a collapsing rubber dome to press together contacts laid out on two sheets of plastic separated by a plastic spacer.

I’m not going to give detailed steps, since other keyboards are probably a bit different, but here are my notes:

  • I used Aqua’s Key Test which I found via to test each key so I knew where to look for problems.  It’s very hard to test all the keys using a normal program like Notepad.
  • I highly recommend taking plenty of pictures at each stage.  OK, I didn’t, but I had two other keyboards I could look at when putting everything  back together.
  • I used CaiKote 44 to repair broken traces and re-coat unreliable contacts.  I paid ~$6 for the 1.0g jar at Fry’s.  It worked well, although it’s hard to apply precisely, especially using the included applicators, and worked best with a long time to dry (I let it dry for a day before re-testing the keyboard).  The jar looks small, but it does last: I was able to fix up all my keyboards, and a friend fixed a musical keyboard, without running out.
  • I took all key caps off.  I think there’s a chance you could get the keyboard apart with the keys still on, but in any case, I needed to see how I could take everything apart and I wanted to clean the keyboar

Was it worth it?  Yes, because I like the size and feel of these keyboards, and you can’t buy either model today.


December 4, 2011   No Comments