On 4/25/2012 8:47 AM, Pete Keillor wrote:
On Tue, 24 Apr 2012 18:36:55 -0400, Tom Gardnermars@tacks wrote:

On 4/24/2012 7:12 AM, Pete Keillor wrote:
On Mon, 23 Apr 2012 19:24:07 -0500, wrote:

On 4/23/2012 6:56 PM, dpb wrote:
On 4/23/2012 5:34 PM, Tom Gardner wrote:
...

So, how do I get from flowchart to Ladder programming?

http://engineeronadisk.com/V2/book_PLC/engineeronadisk.html

BTW, I ran into the fellow who wrote this at an Embedded Systems
Conference in SF/SJ quite a number of years ago...

http://claymore.engineer.gvsu.edu/~jackh/

He's on faculty at Grand Valley State U in Michigan...

There are lots of other languages that might be suitable, such as
function block, structured text, and phase diagrams. Ladder is my
least favorite, but might be the best choice for your case. AB's phase
diagram programming was undergoing some changes about the time I
retired a couple years ago. I did a lot of AB and some Siemens.
each bump.
If you can do the flowchart, you've done the tough part. Describing
exactly what you want the program to do is a large part of the work.
Still, I found it more and more difficult to focus while programming
after the age of 55 or so. Before that, if you came in my office
while I was working, I probably wouldn't hear you or notice you at
all. I'm a lot easier to interrupt these days.

Pete Keillor

What are phase diagrams? My cousin would make a diagram that would have
square "bumps" on a line that would show if a relay contact or a switch
was on or off. Each contact set would have a separate horizontal line
and somehow he would create the logic by the state of each bump. Is
trhat a phase diagram?

Rockwell has a phase manager, but it was just coming out when I
retired. I played with it a little when one of their software gurus
came out to visit for a couple of days to bounce the concept off me.
Phases are like "Load ingredient A, Load Ingredient B, Stir, Cook,
etc. One I left off that I used more was sequential function chart.

On the projects I worked on I used a lot of function block, some
structured text, a little sfc, and damn little ladder. You can get
most types to do a job, but some are easier for a type of job than
others. For continuous processing (flow meters, pumps, etc) function
block beats ladder hands down. For discrete manufacture(more on-off
type logic), ladder may be the way to go, although I don't like the
stuff and would probably use a different tool. You can find a
downloadable demo for RSLogix 5000 for playing around good for 90
days. It'll give you a good idea of the different types and what they
do, but cost for a working license is what you'd expect for corporate
type projects. They do have cheaper products for smaller jobs. All
of the big control software outfits pretty much conform to S88 now, so
the tools are similar overall, although there are considerable
differences in the details. I sure preferred rockwell to siemens. I'm
guessing there is no german equivalent to "user friendly".

When I first started using Rockwell's software, as a beginner they
reviewed my code under a secrecy agreement. Then they drove over with
the software guru mentioned above. Strange meeting, he sat with me in
my office, showed me some tricks to get everything to work (involving
some vestigial ladder), and the other five people including other
Rockwell folks and our local vendor stood around trying to figure out
what the hell we were talking about. Then they invited me to do a
presentation at one of their user conferences. Fun days.

The guru is a brilliant guy, but they'd moved him to management by the
time I retired.

One thing I'd want is a system that supports indirect addressing. You
name the variables names that make sense and don't worry about where
they're stored. That was not the case in old plc programming, like
plc-5's. Variables were named by their location, which is a real pain
in the ass.

Sorry to run on, you got me going remembering the old days. My job
description was never programmer, but r&d technical leader. I
programmed stuff I designed because I liked it, although it's a poor
career choice. Mostly they hire contract programmers, cheap.

Pete Keillor

Everything I ever need a machine to do is simple. My target project
controls two hydraulic cylinders. The machine makes solid-fill end
brushes. One cylinder holds the cup in a die, the outer cylinder
inserts a bundle of wire, then the first cylinder goes to high pressure
and pushes the cup further into the die that crimps it. As it is now,
there are 3 hydraulic valves, five limit switches and two palm switches
in series. Eight 3 to 4 pole-double throw relays and a 24VAC
transformer is all that's in the control box. This is fairly simple
with a bit of trickiness. It runs fine now but it seems like a good
project to cut my teeth on while eyeing more complex machines.