[sdiy] Controller design

[Ian Fritz]

You can look at my website for my breath-controller experiments to get 
more ideas.  The discrete approach using photosensors is possible, but 
there is alway a large amount of temperature drift.  I show an example 
of T compensation that works reasonably well, but you really need 
well-matched devices to get the best results.  The integrated P sensor 
approach works much better in that recent devices have T compensation 
built in.  But be careful -- you need to have a unit with a very low 
pressure range, which rules out the vast majority of available devices.

Ian

http://ijfritz.byethost4.com/Stealth/st_circ.htm
http://ijfritz.byethost4.com/SoS/sos_cir1.htm