[Paparazzi-devel] Airspeed, and Altimeter Sensors

[Steve Turner]

Hi David,

> for PCBs from advanced circuits, you can use the $33 special for 
prototypes.  I have used
> that in the past and am very pleased with the results.  
https://www.4pcb.com/!33each1.asp

These guys do look like they know what they are doing. The $33 does 
not look as bad, but with a minimum quantity of 3 it is still $100. 
Not too bad, but eurocircuits still looks cheaper. Even after paying 
the shipping.

> Something different...  I am starting on a project simialar to the 
altimeter you have
> listed on your web page.  I was wondering how that turned out, if 
you have used it and if
> you have any hits beyond what is on teh web page?  Same for the 
airspeed indicator.
> 

I did play around with my altimeter, and airspeed sensors for a while. 
They work ok, but could be better. Actually I am rather happy with how 
the airspeed sensor turned out. It seemed to work pretty good, and had 
a decent resolution.
The altimeter could have been done much better however. I did not 
account for non-standard atmosphic conditions like the real airplanes. 
This made things simpler, but the altitude was not always accurate. I 
also could have done better at limiting circuit noise. With the sensor 
I used, a very small voltage variation represented a fair amount of 
altitude. This makes things a little tricky, and my altitude tended to 
move around a bit. I should have also used something more than a 10 
bit ADC, a good clean op amp, and very good voltage references. That 
was the hardest part for me, trying to clean up the signals. I kind of 
gave up on the PIC's because of their frustrating lack of easy math 
capabilities. It's been a while since I have updated the site with 
info.

Steve Turner
Fort Collins, CO
http://www.steveonweb.com