The Amp Hour #571 - Rube Goldbergs in Spaaaace - Who's using PLC's?

[IanJ]

Dave asked, who's using PLC's?

Back in the 90's/2000's I did a lot of PLC programming using Mitsubushi System-Q/Q-Series PLC's & IEC Developer software. This wasn't ladder logic (but you could still write it), it was more graphical.
Really nice to use, you designed or used existing blocks and tied them together. You could still go online with IEC and see all your live data.
I played with Siemens, Allen-Bradley and Toshiba PLC's a little.........but no comparison IMHO!

This is IEC Developer:-

[HuronKing]

My day job involves PLC programming and troubleshooting. It's mainly Allen-Bradley stuff, RSLogix500 and RSLogix5000 programming environments.

A lot of that is being gradually upgraded to Beckhoff CX2030 in TwinCAT3 Visual Studios though.

[H.O]

Yeah, these days most development environments for industrial PLC supports the IEC-61131 standard which in turns defines a couple of different "languages" that can be used, Ladder Diagram being ONE of them. The IEC in GX IEC Developer that Ian shows a screenshot from comes from the fact that tool is IEC-61131 compatible where the older version, simply called GX developer was not. Today I think their (Mitsubishis) recommended tool is GXWorks3. 

I'd say that for anything but the most basic projects you end up using a mix of the different "languages". Dave mentions a state machine for example, that's pretty much what SFC is, you don't need to do an FSM using discrete ladder logic.

Anyway, yes Ladder Diagram is definitely used each and every day but its "definition" might have changed a bit since the 70's. It's not just contacts and coils. In fact, what Ian shows IS Ladder Diagram (as shown by the [LD] designator next to the POU (Program Organization Unit) name in the project tree)