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Basic Stamp PLC style applications — Parallax Forums

Basic Stamp PLC style applications

ArchiverArchiver Posts: 46,084
edited 2000-06-10 17:44 in General Discussion
FYI

This particular project involved changing a machine out to do a
function it was not programmed by the original manufacturer to do. The
original vendor did not wish to support our needed changes (it would
have a nightmare they should not support) to our process.

The reason for doing the board was to eliminate the proverbial rats
nest of as-built projects, which some technicians will turn out, they
work, but are not pretty, nor are they very easy to support. Thus
designing a generic building block module to perform tasks which are
needed to be added to equipment, eliminates all sorts of issues: of
what to build, how to support, spare parts and such.

Everyone should realize that in some cases large I/O are not needed
for a machine function change. In other cases machines can be broken
up into building blocks with each block performing a function.

I am working on several other models and architecture which would
allow BSII modules to perform industrial tasks on a larger scale, with
ever larger I/O capability, 16I & 16O with various addressing schemes
for larger units. This module is simply the smallest of them all. Plus
other modules will have the ability to nicely integrate analog process
functions as well. Thus even if the programming size becomes a
constraint a BSIIsx could be used to expand the programming.

Personally I like distributed processing, as this model of programming
is easier to make changes.

The separate relay you may have seen in the picture was used due to
interface required, not because all outputs need a relay.

In this case we needed to put in a relay who's contacts would parallel
another vac switch which had 2.5-3.0 volts on it which needed to be
pulled to ground, to control a standard logic machine input. If the
machine design by the vendor was different we probably would have
simply put the logic line to the open collector of the output and
would have been done with it. Retaining as much of the original
machine functionality was desired while changing as little as
possible. In our case we used 3 inputs and 3 outputs and a very short
program to accomplish the desired flexibility in this particular
machine project.

In the bypass mode this module was programmed to pass a signal
straight through, thus when the machine is in run mode for this
specific process, this same signal initiates a squence of events based
on other inputs.

This message was sent out as a test for interest in such products and
problem solving. Obviously there is an interest here, so I will be
updating everyone who has replied later on this week with the
specifics they have requested.


*******************************************

On the topic of reliability, I have found the stamp (BSII module) to
be very reliable. I have one application which has been running 7 days
a week, 24 hours a day for the last 19 months. You may have another
definition of reliability, but I find this to be nothing short of
excellent. It speaks well of both Microchip and Parallax and their
products.

Having experience with Allen Bradley, Direct Logic, Keyence and other
PLC and PLC controlled equipment, the issue many times is not always
the brand but the ease of programming and the ability to adapt. The
cost of software is sometimes an issue especially if the vendor deems
their software (for the equipment) is off limits, a black box if you
will.

The cost of sensors for PLC style industrial projects will out strip
the cost of the controlling modules (as previously shown here) with
industrial proximity and optic sensors in the range of 35 to over 200
dollars each, depending on type and needed application.

Most industrial processes occur in a logical order and this can be
easily programmed into a PIC or BSII module. With processes having a
logical order, when I'm waiting for "x" to happen, I could care less
about the other inputs and need not scan them as a PLC does. Thus the
programs look for the specifics during a point in time and should
these conditions be met the appropriate output state is then triggered
and the process continues on. The ease of adding an LCD to this module
is a breeze by comparison to the hoops to be jumped with other PLC's.

Thanks,

Ron Anderson
President
Digitial Design Solutions, Inc.


Original Message
From: "webmaster" <webmaster@k...>
To: "Ronald Anderson" <basicstamps@egroups.com>;
<webmaster@k...>
Sent: Saturday, June 10, 2000 9:20 PM
Subject: [noparse][[/noparse]basicstamps] basic stamp PLC


>
>
> hey ron -->
> your little plc board is very COOL
> i have been playing around with the stamps for 1/2 a year now
> never seen anything like what you made!
> i thought about building one just like yours at one point
> then i started making projects with the stamp
> i realized the stamp is no match to any PLC for the matter of
> reliability
> you can do many great things with a stamp interfaced to a plc
> i currently have a project that involves a 11 channel - 12 bit - 0-5
vdc
> analog
> input chip that sends serial to the stamp then the stamp sends
serial to
>
> a chip that converts it to 5 vdc TTL parallel then in to a TTL PLC
input
> card
> it is pretty good speed wise (but not as fast as a (expensive)
analog
> PLC card)
> also you can go on eBay and buy a AB micrologix for $100 or so
> (with has 20 ins and 12 outs)(granted you have the software and
cable)
> i can see in your picture(one in the panel) the separate relay--
> so if you want to use all 7 outputs as relays you have 7 seperate
relays
>
> or do you have different modles such as the PLCs?
> i'm wondering generally what kind of stuff you control with these?
> i'm wondering what brands of PLCs you have delt with
> and do you know of any plc groups like this stamp one?
> i don't have pictures of it right now but i will soon
> below is a link to a picture of one of my projects
>
>
>
>
>
> http://kevinkuehn.com/main/plcpics/images/row4/row4pic12.jpg
>
>
>
>
>
>
>
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