Newbie question. Boolean algebra and ladder logic.

So hey guys, new here. Long time listener first time poster. Have a question for you. I'm looking to get into some rudimentary programming. Currently I am a second year electrician with a basic background education in electronics. Generally my only experience with plcs is connecting the inputs or possibly adding things with a programmer present. I've recently come across the need for a small controller 8 inputs 5 outputs that I think would be simplified by the use of a ab1200 or a seimens s7200? Rather than using a bunch of relays. My question is... from what I've seen of plc programs ( and that's not alot)are very reminiscent of my boolean algebra/ digital electronics days. Without any specific training in PLCs but understanding the logic is the programming language that difficult to pick up? Furthermore if I was to take a course primarily on Allen Bradley PLCs could I assume that others such as. SEIMENs are mutually intelligible? I'm not sure how intimidated I should be. Your advice is much appreciated.

A good place to start would be Hugh Jack's online book Automating Manufacturing with PLCs. He covers Boolean algebra as a design method. It's a useful design tool but don't get too caught up with it as for many thins it's not necessary.

Unless you already have the Software for the AB or Seimens then I would recommend starting with Automation Direct. I think you can use Directsoft for free if your program is under 100 words. You could download the programming software for free and write your program. If it ends up being less than 100 words then all you'll need is a couple hundred for the controller.

I would say that Siemens (Simatic Manager) and Allen Bradley are completely different from a GUI point of view. Someone with experience in one would be better equipped to tackle the other but there aren't many parallels between them with regards usage etc.

To answer the question of 'what to learn' I would look around at what your local factories primarily use. Look for jobs in the industry you want to work in and look at the requirements for the jobs. If the majority say 'Allen Bradley experience a plus' etc then that will answer your question.

Good luck with it all and, as TConnolly says, don't get too hung up on the abstracts of it all. Just get hold of a copy of the software and have a go at it. Or study print outs of other peoples software and ask questions in this forum and from other experienced people.

;-)

Furthermore if I was to take a course primarily on Allen Bradley PLCs could I assume that others such as SIEMENs are mutually intelligible?

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If Allen Bradley PLCs are mostly the brand used at your workplace, then that is the one to study. All the brands are different in a lot of different ways (that is competition and capitalism and we wouldn't want the government dictating what PLC to use) but that does make it more difficult for a guy just starting to learn about PLCs.

Also, instead of an AB Micrologix1200, the AB MicroLogix1100 would be a better choice. Programming software for the ML1100 is free. The 1100 also offers online programming and Ethernet connectivity.

Wow you guys are awesome. I will definitely study that site thank you T Connelly! I was looking at the seimens because I heard the software was cheaper. I will look at the 1100 as well as the automation direct as well. Thanks for the tips! Also anybody know a good cheap 4-20 display with start stop capability I see alot of carlo gavazzis out here but I dont like them. Was a fan of Precision Digital and have the programmer but I don't know how they are for pricing. Also, if I use transitor outputs for my LED warning lights do I have to worry about leakage current, and would a diode fix this?

For a cheap HMI look at the Optimate from Nematron. I believe AutomationDirect sells them also. For something with more capabilities I'm a big fan of Redlion G3 terminals.

Are you talking about LED lamps or single LEDs? Chances are you won't have a leakage current problem with LED lamps, but with a single LED it might glow a little. A resistor in parallel will help.

As I recall, Allen-Bradley use to have a free version of their 500 software.

http://www.ab.com/linked/programmablecontrol/plc/micrologix/downloads.html

OdinIII said:

Unless you already have the Software for the AB or Seimens then I would recommend starting with Automation Direct. I think you can use Directsoft for free if your program is under 100 words. You could download the programming software for free and write your program. If it ends up being less than 100 words then all you'll need is a couple hundred for the controller.

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The Directsoft programming software is free, with no restrictions. You'll only need to purchase a programming cable.

Bit_Bucket_07 said:

The Directsoft programming software is free, with no restrictions. You'll only need to purchase a programming cable.

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DirectSOFT5? How do you get it for free?

Directsoft has a free demo version limited to 100 steps. Other AutomationDirect platforms, Click, P3000 and DoMore have actually free software.