From flowchart to schematic to ladder

I can design machine control circuits using relay logic but it's a
grueling job for me. I don't do it often enough to be proficient.
Typically, my circuits have 8 or less 344PDT relays with about as many
switches and as many outputs like valve coils and such. I can do a
flowchart in minutes but can't easily translate to a schematic.

We only have a couple of PLC controlled machines. I did the flowcharts
and hired a company to do the programming. I would very much like to
become proficient at doing the whole job in house. I can think of a
number of applications that using PLCs to replace relay boxes would be
very beneficial.

I use a bunch of stuff from "Automation Direct" and I've been looking at
their "Click" line of PLCs. They seem inexpensive and powerful.

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

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

--

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...

--

On Mon, 23 Apr 2012 19:24:07 -0500, dpb 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.

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

Pete Keillor fired this volley in
:

Ladder is my
least favorite, but might be the best choice for your case.

I was a machine language programmer when I was first thrust into the
ladder logic world, and it was a rough transition.

My path was eased when the team decided on a PLC with an event-triggered
BASIC language extension capability. I don't have experience with many
different PLCs, but from what I've seen, most of them offer some such
ability.

It allows you to place the most fundamental cyclic state checks in
ladder, and do the nitzy (and perhaps arithmetic-based) control in the
'higher' language.

In the case of the BASIC I was given, it was severely crippled, and
required that I write my own floating-point math package to support the
precision of work we were doing.

The learning curve was pretty steep, but short.

LLoyd

I'll chime in on this PLC thing. I have a lot of experience using
different different computer languages to control equipment.

I always found PLC ladder logic to be difficult and arcane. I do know
the folks that do this can whip out a control program quickly.

If you don't have a fella with great aptitude for this sort of thing
in house, I'd hire it out. An expert will charge ya, but it will be
worth it.

Karl

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?

On Tue, 24 Apr 2012 18:36:55 -0400, Tom Gardner mars@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

On 4/23/2012 8:24 PM, dpb 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...

--

Thanks, lots of good stuff here!

On Mon, 23 Apr 2012 18:34:09 -0400, Tom Gardner mars@tacks wrote:

From flowchart to schematic to ladder

I can design machine control circuits using relay logic but it's a
grueling job for me. I don't do it often enough to be proficient.
Typically, my circuits have 8 or less 344PDT relays with about as many
switches and as many outputs like valve coils and such. I can do a
flowchart in minutes but can't easily translate to a schematic.

We only have a couple of PLC controlled machines. I did the flowcharts
and hired a company to do the programming. I would very much like to
become proficient at doing the whole job in house. I can think of a
number of applications that using PLCs to replace relay boxes would be
very beneficial.

I use a bunch of stuff from "Automation Direct" and I've been looking at
their "Click" line of PLCs. They seem inexpensive and powerful.

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

Start simple and build on it! Start by replacing a single timer or
something like that. Don't start with a whole machine unless you can
block out a whole bunch of uninterrupted time to bootstrap things.

PLCs are the right tool for your applications, IMHO, you just have to
play with them a bit more. You might want to start with a micro-PLC
that doesn't have zillions of features, and then move to something a
bit overqualified for your applications that you can standardize on.

The nice thing about being in full control of the programs is that you
will be able to tweak them without getting someone in.

BTW, I would be sure to implement any safety-related requirements
outside of the PLC. For example, don't route an e-stop switch or an
overtemperature alarm through the PLC logic, make it actually shut
things down positively if human safety could be compromised. That way
a PLC failure, glitch or programming error can't hurt anyone.

Spehro Pefhany fired this volley in
:

That way
a PLC failure, glitch or programming error can't hurt anyone.


Yeah... and they do happen, even if your code is pristine.

LLoyd

On 4/25/2012 10:11 AM, Spehro Pefhany wrote:
On Mon, 23 Apr 2012 18:34:09 -0400, Tom Gardnermars@tacks wrote:

From flowchart to schematic to ladder

I can design machine control circuits using relay logic but it's a
grueling job for me. I don't do it often enough to be proficient.
Typically, my circuits have 8 or less 344PDT relays with about as many
switches and as many outputs like valve coils and such. I can do a
flowchart in minutes but can't easily translate to a schematic.

We only have a couple of PLC controlled machines. I did the flowcharts
and hired a company to do the programming. I would very much like to
become proficient at doing the whole job in house. I can think of a
number of applications that using PLCs to replace relay boxes would be
very beneficial.

I use a bunch of stuff from "Automation Direct" and I've been looking at
their "Click" line of PLCs. They seem inexpensive and powerful.

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

Start simple and build on it! Start by replacing a single timer or
something like that. Don't start with a whole machine unless you can
block out a whole bunch of uninterrupted time to bootstrap things.

PLCs are the right tool for your applications, IMHO, you just have to
play with them a bit more. You might want to start with a micro-PLC
that doesn't have zillions of features, and then move to something a
bit overqualified for your applications that you can standardize on.

The nice thing about being in full control of the programs is that you
will be able to tweak them without getting someone in.

BTW, I would be sure to implement any safety-related requirements
outside of the PLC. For example, don't route an e-stop switch or an
overtemperature alarm through the PLC logic, make it actually shut
things down positively if human safety could be compromised. That way
a PLC failure, glitch or programming error can't hurt anyone.


Good ideas, thanks!