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ladder logic for PLC

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haxor5354

Fri Oct 29 2010, 02:44AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

i've picked up an old misubishi PLC from a junk pile at an surplus store, the model number is FX1s-10MR-001
i got the programming cable and softwar, and tested a sample program
anyone here knows how to program PLCs with ladder logic

the worst thing i hate about programming in ladder logic is that the outputs don't have registers
i need a program that when input 1 is activated, output 1 turns on, if input 1 is activated again output 1 turns off

dmg

Fri Oct 29 2010, 03:44AM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

hello,
Ive got a mitsubishi FX2N series, not the FX1s, but IIRC, they are pretty simular.. do you have a picture of the thing? im sure it has two sets of screw terminals, being X and Y.

X are inputs and Ys are your outputs, also, what program are you using for it?
I used GX developer.
most of them have pre-set functions that you can select (for example: M8032 (not exact #, but started with M.. im a bit rusty on this) for my PLC, which is a coil that is a preset function for a 1 second pulse.
writing on ladder logic for these functions will look something like this:

----------{x001}----[M8032]---------------- (Y001)-----
-------------------------------------- ----[END]------------

where the terminal on the X side (labeled 1) will be an input (mine is just wire shorted from RUN to X terminal/s used)
Y is the outputing relay, where it will be opened/closed at 1 second intervals,
and M, is the preset function that exists on the PLC.

usually there are "blocks" of screws, where they have a common point for a set of relays.
so you will have to wire Y1 and COM to have a relay to do something, which for example can open/close another X input, so lets say 1 second wait, Y1 closes, which is a relay for X2, and it will perform another function, and so on so forth, or they can be controlling whatever you want it to do.

At least thats how my PLC was working.
try finding a manual on the thing, it should have a full list of preset functions for you to mess with before writing your own commands.
if someone else here used these ones before, and you spot an error, let me know. It has been too long since ive played with it.

haxor5354

Fri Oct 29 2010, 06:59PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

and i just picked up a variable frequecy "thngie" that takes 50/60 Hz 3 phase AC and make them 0.2-400Hz AC
and are 9600uf 400v electrolytic capacitors for $15.00 each a good buy?
Dsc00996mn

[Edit: Image size]

Renesis

Sat Oct 30 2010, 05:24PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

I've written a few programs in ladder using Simatic Step 7. I havent tried Mitsubishi or GX developer yet.

The program you describe is basically a "toggle". Often ladder programs have a function block for the toggle function that you can use, especially if the PLC is of a newer date.

I had the same problem once, and if i remember correctly, i ended up using two counter functions. One counting to 1, the other counting to 2. Like this:

Â Â Â Â I0 Â Â Â Â Â Â Â C0
---[Â ]-----[CÂ Â Â Â Â Â Â ]
Â Â Â Â Â Â Â Â Â Â Â Â [Â CupÂ Â ]
Â Â Â Â C1 Â Â Â Â [Â Â Â Â Â Â Â Â Â ]Â Â Â Â Â
---[ ]-----[RÂ Â Â Â Â Â Â ]-1

Â Â Â Â C0 Â Â Â Â Â Â Â Q0Â Â Â Â Â Â Â Â
---[ ]--------( )

Â Â Â Â I0 Â Â Â Â Â Â Â C1
---[Â ]-----[CÂ Â Â Â Â Â Â ]
Â Â Â Â Â Â Â Â Â Â Â Â [Â CupÂ Â ]
Â Â Â Â C1 Â Â Â Â [Â Â Â Â Â Â Â Â Â ]Â Â Â Â Â
---[ ]-----[RÂ Â Â Â Â Â Â ]-2

In Simatic the inputs are referred to as In and the outputs are referred to as Qn. Cn are counters, Tn are timers and memory bits (or fake outputs if you will) are Mn. All of them can be used as switches within the program.

Ladder is a language that is really easy to learn, and you dont need to know anything about processors and registers and such to use it. Thats why it has become so popular with PLC's.

You say you miss registers in ladder programming, but you can still use memory's on the outputs. Again, in Simatic:

Â Â Â Â I0Â Â Â Â Â Â Â Â Q0
---[Â ]---- --(S)

Â Â Â Â I1Â Â Â Â Â Â Â Â Q0
---[Â ]------ (R)

Here you have a program for say, office lighting. A signal on the input I0 turns the light on (output Q0), and a signal on the input I1 turns the light off. Basically a Set-reset latch. And in Simatic there is also a function block for the SR-latch:

Â Â Â Â I0Â Â Â Â Â Â Â Â Â Â Â Q0
--- [Â ]-----[SÂ Â Â Â Â Â ]
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [Â S/RÂ Â ]
Â Â Â Â I1Â Â Â Â Â Â Â Â [Â Â Â Â Â Â Â Â ]
--- [Â ]------[RÂ Â Â Â Â Â ]

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