PicDude wrote:
> I can electrically control the compressor on/off, and get an 
> electrically-actuated valve to bleed the pressure.  What I need is a software 
> program that (a) has output lines to control the valves, (b) can read an LED 
> display (as I suspect that modifying the application circuit to produce a 
> serial or other output would/could affect the calibration of that circuit),  
> (c) has a simple programming/scripting language so I can automate the 
> process.  

Not sure what your budget is, but I would lean towards and E/P regulator 
instead of cycling your compressor on/off.  These typically take a 0-5 
volt, or 0-10 volt signal and give a proportional pressure output.  
(Watch out, though, as some are not zero based.)  Most require an actual 
pressure transducer as a feedback device for the controller.  (Some do 
have built-in pressure transducers.)  The  pressure transducer would 
eliminate the need for a way to read your pressure gauges... simply use 
an A/D converter.  Use a PIC to control it all and and spit the data out 
to your PC via an RS232 port for logging. 

You should be able to get an E/P regulator and transducer for 
$300-500ish.  Check out:
http://www.marshbellofram.com/PCD/3110_3120.htm  (Looked promising last 
time the sales rep visited.)
http://www.controlair.com/transducers.html   (I've used their open-loop 
T500x controllers, but they aren't zero based.)
http://www.proportionair.com/family_pressure.asp  (I've used their QB1 
before.)

Aaron
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