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 4/24/2012 5:27 PM, Karl Townsend wrote:
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

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my shoes?

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!

Tom Gardner mars@tacks fired this volley in
:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.

Lloyd

"Tom Gardner" mars@tacks wrote in message
...
On 4/24/2012 5:27 PM, Karl Townsend wrote:
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

I'm at the age where I feel the need to challenge my brain to keep
it functioning. What control scheme would you learn if you were in
my shoes?

If given the choice I code a state machine controlled by global
Boolean variables, which roughly correspond to the relay coils. The
comments that describe its operation come first and replace a
flowchart.

I learned to decipher and then design relay ladder logic shortly
before PLCs came out.

jsw

On 4/24/2012 5:41 PM, Tom Gardner wrote:
On 4/24/2012 5:27 PM, Karl Townsend wrote:
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

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my shoes?


Assembly language...

No secrets, not high level help, total responsibility,
but total control.


Then write any damned thing you want...

On 4/24/2012 6:13 PM, Lloyd E. Sponenburgh wrote:
Tom Gardnermars@tacks fired this volley in
:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.

Lloyd


I think I'm going to dig into the Arudino as well.
The Propeller is a hell of a lot more powerful processor,
but you don't always need that.

"Lloyd E. Sponenburgh" wrote in message
. 3.70...

Tom Gardner mars@tacks fired this volley in
m:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.

Lloyd

I found some good PDF files for Arduino, mostly just searching Arduino PDF.

I'm learning more useful Arduino programming with the gnu-c-manual.

I used to write ladder type rungs with the if() statement, now I kind of
like:

Output = (((A && B)||C)? 1:0) ;

instead of:

If((A && B)||C) Output = 1; // If (A AND B) OR C, Output is turned on
else Output = 0; // else Output is turned off.

Seems like an interesting little shortcut.

I was able to use pointers to structures to use one function with multiple
sets of data, I did PLC style timers with each instance of the timer having
it's own data so I can set multiple timers.

I'm not very good at it but it's been fun learning.

RogerN

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 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 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.

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!

On Wed, 25 Apr 2012 10:54:15 -0400, Tom Gardner mars@tacks wrote:

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.

Spehro has a good suggestion, use a microcontroller. Possibly simpler
instruction set and a lot cheaper. Some can later be integrated into
larger systems if you have a need.

Pete Keillor

"Tom Gardner" wrote in message
...
snip

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.

Are the two buttons in series to keep the operators 2 hands on the buttons
while the machine is running?

A nice way to do two hand trip control in a PLC.

Have a timer to start timing on these 2 conditions, button 1 is ON and
button 2 is OFF, OR button 1 is OFF and button 2 is ON. The timer may be
something like a half second or so. This timer rung will have a third
condition that holds it on, that is the timer is done and either button 1 or
button 2 is ON.

This prevents the operator from tying down a button and operating from just
1 button. Since the timer seals itself in if either button is ON, both
buttons must be released to reset the start condition.

Ok, the next rung would be if button 1 is ON and button 2 is ON and Timer is
not done, then start the sequence.

If the 2 hand trip control sequence is started the turn on clamp cylinder
low pressure.

If Clamp cylinder is extended to the clamp position, extend the insert wire
cylinder.

If wire insert cylinder extended then turn on high pressure to clamp
cylinder.

Dwell timer for high pressure?

if high pressure step complete then retract cylinders.

if cylinders retracted and buttons released then cycle reset.

The cycle start condition from the buttons will need to be in every rung
that causes motion so that when a button is released the cylinder stops.

Perhaps you could have it so that it remains in cycle unless both buttons
are released. That way if operator needs to he can release either button,
the motion will stop, but the sequence will continue once the operator holds
the other button again. This would sort of be like a jog mode allowing
operator to stop and continue the sequence.

Just some ideas.

RogerN

On Tue, 24 Apr 2012 18:41:52 -0400, Tom Gardner mars@tacks wrote:

On 4/24/2012 5:27 PM, Karl Townsend wrote:
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

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my shoes?

MAN I HEAR YA. If i don't use it, I'll lose it. I keep writing stuff
for my CNC control to try and keep it. It takes me ten times longer
than it used to and I just don't see mistakes in coding like I did
twenty years ago. Still, if I quit trying, I'd just as well fold up.

I almost bought the PLCs and software offered on automation direct.
I'd suggest you try that offer. You'd be real smart to *pay* for a
tutor.

Karl

On 4/25/2012 6:27 PM, RogerN wrote:
"Tom Gardner" wrote in message
...
snip

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.

Are the two buttons in series to keep the operators 2 hands on the buttons
while the machine is running?

A nice way to do two hand trip control in a PLC.

Have a timer to start timing on these 2 conditions, button 1 is ON and
button 2 is OFF, OR button 1 is OFF and button 2 is ON. The timer may be
something like a half second or so. This timer rung will have a third
condition that holds it on, that is the timer is done and either button 1 or
button 2 is ON.

This prevents the operator from tying down a button and operating from just
1 button. Since the timer seals itself in if either button is ON, both
buttons must be released to reset the start condition.

Ok, the next rung would be if button 1 is ON and button 2 is ON and Timer is
not done, then start the sequence.

If the 2 hand trip control sequence is started the turn on clamp cylinder
low pressure.

If Clamp cylinder is extended to the clamp position, extend the insert wire
cylinder.

If wire insert cylinder extended then turn on high pressure to clamp
cylinder.

Dwell timer for high pressure?

if high pressure step complete then retract cylinders.

if cylinders retracted and buttons released then cycle reset.

The cycle start condition from the buttons will need to be in every rung
that causes motion so that when a button is released the cylinder stops.

Perhaps you could have it so that it remains in cycle unless both buttons
are released. That way if operator needs to he can release either button,
the motion will stop, but the sequence will continue once the operator holds
the other button again. This would sort of be like a jog mode allowing
operator to stop and continue the sequence.

Just some ideas.

RogerN



Yep, that's the cycle, it can be even simpler without the added safety.
The HP cycle end is a limit switch and the operator can hit a switch
that's in series with it and reset the machine. No need to jog it or
troubleshoot, we get about 1 in 2,500 that something goes wrong. I
certainly like using the timers though!

"Tom Gardner" wrote in message
...

On 4/25/2012 6:27 PM, RogerN wrote:
"Tom Gardner" wrote in message
snip
Just some ideas.

RogerN



Yep, that's the cycle, it can be even simpler without the added safety. The
HP cycle end is a limit switch and the operator can hit a switch that's in
series with it and reset the machine. No need to jog it or troubleshoot,
we get about 1 in 2,500 that something goes wrong. I certainly like using
the timers though!


You can get the controller that you choose and write the program for it and
start learning and testing.

You can parallel all the inputs and outputs with memory bits.

After your control program, write some rungs that simulate the machine
operation.

Such as: If Cylinder_Extend_Valve start ~3 second timer, when timer done
turn on Cylinder_Extended_switch. That way you can "press the start button"
in simulation and see that the entire sequence works, before ever touching a
wire on the machine. If you have spare buttons you could even wire in your
2 hand trip control, if the timer is right it's easy to operate but
difficult to fool.

The difficulty I had in getting into ladder logic from other programming is
you have to program the sequence by knowing all rungs are scanning all the
time and the sequence is controlled by conditions like step 1 done enables
step 2, step 2 done enables step 3...

RogerN

On Thu, 26 Apr 2012 05:51:10 -0500, "RogerN"
wrote:

"Tom Gardner" wrote in message
...

On 4/25/2012 6:27 PM, RogerN wrote:
"Tom Gardner" wrote in message
snip
Just some ideas.

RogerN



Yep, that's the cycle, it can be even simpler without the added safety. The
HP cycle end is a limit switch and the operator can hit a switch that's in
series with it and reset the machine. No need to jog it or troubleshoot,
we get about 1 in 2,500 that something goes wrong. I certainly like using
the timers though!


You can get the controller that you choose and write the program for it and
start learning and testing.

You can parallel all the inputs and outputs with memory bits.

After your control program, write some rungs that simulate the machine
operation.

Such as: If Cylinder_Extend_Valve start ~3 second timer, when timer done
turn on Cylinder_Extended_switch. That way you can "press the start button"
in simulation and see that the entire sequence works, before ever touching a
wire on the machine. If you have spare buttons you could even wire in your
2 hand trip control, if the timer is right it's easy to operate but
difficult to fool.

The difficulty I had in getting into ladder logic from other programming is
you have to program the sequence by knowing all rungs are scanning all the
time and the sequence is controlled by conditions like step 1 done enables
step 2, step 2 done enables step 3...

RogerN


But unlike hardwired relays, executes sequentially, just over and
over. So only define each output once, or last definition always wins.
Also, write rungs as series for AND conditions (inputs) and parallel
for OR conditions, just like wiring relays.

On 4/25/2012 8:06 PM, Karl Townsend wrote:
On Tue, 24 Apr 2012 18:41:52 -0400, Tom Gardnermars@tacks wrote:

On 4/24/2012 5:27 PM, Karl Townsend wrote:
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

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my shoes?

MAN I HEAR YA. If i don't use it, I'll lose it. I keep writing stuff
for my CNC control to try and keep it. It takes me ten times longer
than it used to and I just don't see mistakes in coding like I dide are a couple of local vendors that of
twenty years ago. Still, if I quit trying, I'd just as well fold up.

I almost bought the PLCs and software offered on automation direct.
I'd suggest you try that offer. You'd be real smart to *pay* for a
tutor.

Karl

There are a few local vendors that offer training on their products, do
you have any preferences like AB or such?

Tom Gardner mars@tacks fired this volley in
:

There are a few local vendors that offer training on their products, do
you have any preferences like AB or such?

Fifteen or twenty years ago, AB and a couple of others were the only
decent PLCs around, and everyone used them for everything.

Now there are lots of Pacific Rim companies making dandy, inexpensive
PLCs.

You might investigate TRI-Plc. They are inexpensive "board" solutions
(no fancy plastic cabinet). Despite that basic nature, they're capable,
reliable, and easy to learn. They have hundreds of sample programs in
their downloads area to help you learn.

They're also readily expandable, with extra ports, extra program or data
memory, and a real-time clock. It has an event-triggered BASIC language
extension built-in, and all the programming utilities and simulator come
with it for free. It's also web-enabled. Just plug it into your
network, and you can access and program it from anywhere you have an
internet connection.

It's a cheap way to get into the groove. Then if you want to go to a
'classic' brand, you'll have some experience under your belt.

"Lloyd E. Sponenburgh" wrote:

Tom Gardner mars@tacks fired this volley in
:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.


Have you looked at at Aurdino G-code software?


--
You can't have a sense of humor, if you have no sense.

Richard wrote:

On 4/24/2012 6:13 PM, Lloyd E. Sponenburgh wrote:
Tom Gardnermars@tacks fired this volley in
:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.

Lloyd

I think I'm going to dig into the Arudino as well.
The Propeller is a hell of a lot more powerful processor,
but you don't always need that.


The Aurdino family has a lot of boards to chose from, and there is at
least one website that shows you how to convert one of the super cheap
Aurdino proggrams into a controller by cutting a few traces, and adding
a few jumpers. Those boards are under $10, and sometimes under $5.

'USBASP' or 'USBISP'. I have the articles saved on a backup drive, but
I can find the links or email them to you.

--
You can't have a sense of humor, if you have no sense.

"Michael A. Terrell" fired this volley in
m:


Have you looked at at Aurdino G-code software?


No! Tell me more!

Lloyd

"Lloyd E. Sponenburgh" wrote:

Michael A. Terrell wrote:

Have you looked at at Aurdino G-code software?

No! Tell me more!


I'll have to look for the websites again, but I was looking for
'Aurdnio+CNC' when I stumbled across a reference to it.


--
You can't have a sense of humor, if you have no sense.

On 4/26/2012 10:30 AM, Lloyd E. Sponenburgh wrote:
Tom Gardnermars@tacks fired this volley in
:

There are a few local vendors that offer training on their products, do
you have any preferences like AB or such?

Fifteen or twenty years ago, AB and a couple of others were the only
decent PLCs around, and everyone used them for everything.

Now there are lots of Pacific Rim companies making dandy, inexpensive
PLCs.

You might investigate TRI-Plc. They are inexpensive "board" solutions
(no fancy plastic cabinet). Despite that basic nature, they're capable,
reliable, and easy to learn. They have hundreds of sample programs in
their downloads area to help you learn.

They're also readily expandable, with extra ports, extra program or data
memory, and a real-time clock. It has an event-triggered BASIC language
extension built-in, and all the programming utilities and simulator come
with it for free. It's also web-enabled. Just plug it into your
network, and you can access and program it from anywhere you have an
internet connection.

It's a cheap way to get into the groove. Then if you want to go to a
'classic' brand, you'll have some experience under your belt.


Funny you mention them, I have a 8 I/O relay model kicking around here
somewhere. I had forgotten all about it and I forget exactly what we
got it for...probably some hair-brained idea that got shelved. I'll dig
it out and re-reserech it.

"Lloyd E. Sponenburgh" wrote in message
.3.70...

Tom Gardner mars@tacks fired this volley in
m:

I'm at the age where I feel the need to challenge my brain to keep it
functioning. What control scheme would you learn if you were in my
shoes?

Both, Tom. It's the only way I stay at "medium alert" as opposed to just
plain "old and dumb"! I'm learning on an Arduino chip now, as an
alternative to PLCs.

Lloyd

I'm gradually working toward trying to make a library of functions to make
it easier to write PLC type programs in an Arduino. This will allow the
Arduino to control several things at once instead of doing one thing at a
time. I think the correct name for it is non-preemptive multitasking. The
loop runs through continuously as fast as it can, like PLC scans, and
conditions control the sequence. So far my biggest "PLC like" addition is a
time on delay. I also made a counter function using the same data structure
type as the counter. Anyway the timer is a single function that can be
called multiple times using a different timer data for each event I'm using
a time delay for. If I want to read a sensor every 0.1 seconds, read
another sensor every 5 seconds, and update the display every half second, no
problem.

I got my load cell scale working pretty good so far but still have several
things to add. For one l only have it displaying in decimal pounds, I want
to add units later. I'm wanting to be able to plug in different load cells
to this scale display depending on what I'm wanting to weigh. Once I get a
load cell set up and calibrated, I want to be able to name that load cell
data structure an appropriate name and save to eeprom. Then if I change
scales I should be able select the load cell data name from the display and
load the relevant calibration data and is should be ready to go.

RogerN

"RogerN" fired this volley in
m:

his will allow the
Arduino to control several things at once instead of doing one thing
at a time. I think the correct name for it is non-preemptive
multitasking.

Most PLCs that have an event-triggered extension language would have to be
qualified as doing "preemptive multi-tasking". Once off in a module, you
can't service the ladder until the routine returns. Some don't even permit
servicing I/Os _during_ the routines, only setting internal registers that
will be transferred to the hardware once the ladder loop resumes.

Lloyd

\"Lloyd E. Sponenburgh" wrote in message
.70...

"RogerN" fired this volley in
om:

his will allow the
Arduino to control several things at once instead of doing one thing
at a time. I think the correct name for it is non-preemptive
multitasking.

Most PLCs that have an event-triggered extension language would have to be
qualified as doing "preemptive multi-tasking". Once off in a module, you
can't service the ladder until the routine returns. Some don't even permit
servicing I/Os _during_ the routines, only setting internal registers that
will be transferred to the hardware once the ladder loop resumes.

Lloyd

Right off the bat I can't think of a single PLC instruction that I can't
duplicate in an Arduino. The key to the whole idea is that you NEVER go
"off in a module" where you can't service the ladder. I linked a program I
wrote for a bulb machine I wrote using a Mitsubishi PLC that operates 16
stations. There isn't any part of the program I wrote that needs any kind
of multi-tasking, even though all 16 stations do their thing at the same
time. It's just a matter do doing one thing at a time, but doing it so fast
that it appears to be done all at once. You simply don't program to make
the processor wait for something to happen.

Here's an example from radio control, if you've ever messed with a somewhat
modern radio control system, with an 8 channel R/C system, you can have 8
servo's connected to the receiver and they will all do what you command them
to do simultaneously. In actuality, the transmitter sends a 4.5 millisecond
sync pulse then a series of 8 pulses (for 8 channels) ranging from 1 to 2
milliseconds. A 1.5 millisecond pulse sends the servo to mid position, a
1ms pulse sends the servo all the way one way, a 2ms pulse sends the servo
all the way the other direction. So in millisecond time, one servo is
controlled at a time, but in human time all servos are controlled at once.
Same thing with the PLC program I wrote for the bulb assembly machine, it
has over 5000 instructions, only 1 instruction is executed at a time but
since all instructions are executed dozens of times per second, it appears
everything is happening at once.

I guess the point I'm trying to get at is that in machine control you can
write a bad programs that use multi-tasking, that has a thousand threads
each holding up execution until the programmed event. Or you can have a
single loop that is written to detect the conditions you are looking for to
process the program. The only time I need interrupts is to do something
like serial communication or track an encoder position. Seems like the more
modern technology I see, the more I'm amazed with the Commodore 64.

RogerN

"RogerN" fired this volley in
m:

I guess the point I'm trying to get at is that in machine control you
can write a bad programs that use multi-tasking, that has a thousand
threads each holding up execution until the programmed event. Or you
can have a single loop that is written to detect the conditions you
are looking for to process the program. The only time I need
interrupts is to do something like serial communication or track an
encoder position. Seems like the more modern technology I see, the
more I'm amazed with the Commodore 64.

Your point is well taken, and anyone experienced in low-level programming
( say interrupt-driven M/L) would be easily able to do what you
prescribe.

You may easily be able to do that in an Arduino programming environment
(in which I presently have insufficient experience), but it's not always
possible in commercially-available PLCs. This conversation was taking
the tack about how you can do things like that with a PLC.

I am from the old-school M/L situation, where I not only wrote the
application, but usually wrote the underlying OS and designed the
hardware. In that scenario, it is "easy" to do simultaneous control of
numerous processes. Just get out the assembler, and DO it!

LLoyd

"Lloyd E. Sponenburgh" wrote in message
.70...
snip

I am from the old-school M/L situation, where I not only wrote the
application, but usually wrote the underlying OS and designed the
hardware. In that scenario, it is "easy" to do simultaneous control of
numerous processes. Just get out the assembler, and DO it!

LLoyd

That's awesome, if you have seen the example programs these days you know
where I'm coming from.

I was taught things like:

Loop:
If start_button_not_pressed then goto Loop
motor_run_contactor = 1
Loop2:
if stop_button_not_pressed goto Loop2
motor_run_contactor = 0
goto Loop

Things like that completely tie up the processor waiting for a button to be
pressed, and the processor will do nothing else unless there are interrupts
or some sort of multi-tasking operating system to handle it.

What they should be teaching would be more like

Loop:
If start_button_pressed then motor_run_contactor = 1 (or do other
processing that button press requires) // no holding up processor waiting on
a button to be pushed
if stop_button_pressed then motor_run_contactor = 0

.... //here you can do things that need to be done if the button has been
pressed or not.
.... // or add other code that can execute every loop
....
....

goto Loop

Now to prevent something like the processor being tied up, and not
responding to the buttons, you would use a watchdog timer to reset if a
single iteration of the loop took too long.

I learned to stop programming like the typical examples and start
programming free running loops by both a more experienced programmer and by
learning to program PLC ladder logic.

I can't speak for others but I know learning by bad examples made it more
difficult for me to get a program to handle more than one thing at a time.

RogerN

"Lloyd E. Sponenburgh" wrote in message
. 3.70...
snip
LLoyd

A little off the topic here, but do you think that INA125 board would be
able to work with a single 5V supply? Maybe with a little modification?

RogerN

"RogerN" fired this volley in
:

A little off the topic here, but do you think that INA125 board would be
able to work with a single 5V supply? Maybe with a little modification?


Sure, it will. The reason I don't like to do that is most DAQs handle
swings of at least +-5v, and many +-10V. If you use a DAQ with +-10V input
swing, and a load cell amp that only swings +0.5v to +4.5 volts, you've
'wasted' a lot of bits of precision on the DAQ.

Lloyd

On 4/28/2012 8:37 AM, RogerN wrote:
....

I can't speak for others but I know learning by bad examples made it more
difficult for me to get a program to handle more than one thing at a time.
....

A source of value...

http://www.eetimes.com/design/embedded

I've followed Jack's "Embedded Muse" from its inception--interesting
ideas come through frequently and the tales of experience are worth the
look if for no other reason...

http://www.ganssle.com/

Not directly applicable to PLCs but if you're writing embedded code or
otherwise involved w/ hardware/software interfacing, it's good stuff...

From a distant past, did a lot of work for Remotec on early versions of
what evolved into the Andros Mark V robots. The specific version we
shipped was for man-replacement use in commercial nuclear power plants
and was equipped w/ a manipulator or optional instrumentation package.
It was three Motorola 68k's (two onboard/one operator console) in VME
bus running under CP/M w/ the control software written in Forth...

That was about 10 years prior to this press release when Remotec was
still a relatively new startup...

http://www.policeone.com/police-technology/press-releases/83197-Remotec-Announces-the-ANDROS-MARK-V-A1/

--