On 07/12/2010 02:27 PM, RogerN wrote:
"Tim wrote in message
...
On 07/11/2010 10:58 PM, Buerste wrote:
I'm working on a design for a machine that will make a number of
different
yet similar products. There will be 2 servos and a stepper to do the
bull
work yet there is one air cylinder that will provide pressure on
material.
The amount of pressure will vary from one product to another and from one
kind of material to another. I'd like to automatically change the air
pressure within the program for each product/material. Such a thing?
No,
I'm not going to build one. If it ain't off the shelf, it won't happen.


Aw, c'mon. You just need a solenoid valve, a fancy PLC with high-speed
PID, an accumulator and pressure feedback. Oh, and several days of
dinking around, but it'll be fun so that won't matter.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Well, if there were only a few pressures you could set each pressure with
manual regulators and select with valves.

A person might be able to do a pretty good job with a small air tank, a
pressure transducer, and a valve or two. Inflate tank to pressure, shut off
valve, when tank gets low, turn on valve automatically. Maybe an op amp
with some hysteresis to compare setpoint and transducer?

That would be one way. It's basically what a mechanical regulator does,
except that the mechanical regulator does it -- well -- mechanically,
and powered by the pressurized gas:
http://en.wikipedia.org/wiki/Pressure_regulator.

I have no clue if anyone actually does this, mind, or if there's any
sane reason to do so when mechanical regulators work so well.

But it'd be fun...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html