Replies to This Discussion

ModeratorPermalink Reply by Chris Anderson on August 1, 2008 at 4:41pm

I think as long as you have six thermopiles, you should be okay. With all six, they work fine in everything but fog and rain.

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Permalink Reply by helder on August 4, 2009 at 10:01am

Hi Paul,
I have the new FMA copilot2 sensors which happen to do the digital thing.(Didnt know it was different??)
So i wanted to know if you ended up using digital thermopiles also as im stuck!
You see, on the main page
http://diydrones.com/profiles/blogs/ardupilot-main-page
it says 6 "spare" analogue and 6 "spare" digital i/o.
But on
http://api.ning.com/files/DLK488CztD53XnoYvHZWMgYIHASthJCwBpLCYY4qh...*DVQQwo0kiC9gzSME0iZmPO8v6JZ8GR/DSC05807.JPG_website it looks like there is only 1 analogue "available" and 1 digital "available?
How do i get 6 digital thermopiles to connect to 1 digital i/o or ardupilot?
Should i try this way?
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1231672744
But i dont know if digital i/o is the same as i2c i/o!
Any ideas would be great.
Thanks

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ModeratorPermalink Reply by Chris Anderson on August 4, 2009 at 10:28am

Helder,

I don't know any way to use the FMA digital sensors. Even if you could figure out the communications standard, ArduPilot with the shield has used all the digital pins. I'd suggest you use it as ArduPilot 1.0 (navigation-only) and let the FMA CoPilot do its job.

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ModeratorPermalink Reply by Sgt Ric on August 4, 2009 at 10:53am

Good point Chris,
The thermopiles, by defintition, do not supply any logical input other than on/off and are not needed for the GCS or OSD really, so why try so hard to integrate digital into the A/P?

Not being an elctronic engineer (or good speller), I don't know why FMA (Revolectrix) uses digital signal?
(Obviously finer resolution, but what would Ardupilot need with that data?}

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ModeratorPermalink Reply by Giles Barton-Owen on August 5, 2009 at 2:12am

But you could use one of the then unused Analog I/O pins as digital (pins 4,5 are I2C). U have to address them as pins 14,15,16,17,18,19,20,21 (I think).

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Permalink Reply by bGatti on August 5, 2009 at 7:13am

I think more prescient than analog or digital to the processor is n signals, or n/2 signals to the processor where n is the number of thermophiles. In the current configurations, a pair of thermos are differentially amplified on the board resulting in a single signal to the co-/auto-pilot. One cannot be blamed for thinking that 3 sensors at 60 degrees are in fact as sufficient as 4 at 90, and that 4 in a 3-pyramid formation may well be as good as 6 in cubic (in each case using the computed average against the individual sensor.) But this requires all signals to be amplified and converted, resulting in more wires, more amplifiers, and more processor time against lower cost and weight.

I don't have an answer, but this seems to be the question being asked.

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Permalink Reply by Dave_fr on August 22, 2009 at 2:32am

Are the thermopile readings linear ?
I watched a video of attopilot flight and the attitude control seems to be much more accurate when the plane is straight and leveled than when it is in a turn with some bank.
You can watch this video where the guy went round that problem by creating a tiltable platform. http://www.youtube.com/watch?v=Vpf21XS09TQ&hl=frhttp://www.yout...

I'm learning on thermopiles because, if it's possible to use them to accurately determine the bank, then it would also be possible to determine the rate of turn (we know the airspeed). In my opinion, knowing the rate of turn is crucial information, because by combining this with a gps headings through a Kalman filter we would be able a have an instantaneous reading the heading. Even with 1hz gps, we could have as many readings as possible and ardupilot would be able to set course to next way point within a flick of a finger lol.

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