Thermopiles can be used for horizon detection - FMA, Paparazzi, and the new boards Chris and Jordi have designed up.I believe these all output analog to the main board where they are digitized and acted upon. If true, are there reasons that digitization should not take place near the sensor and output a serial result to the main board?In this mode, a three wire connection (like a servo wire) could provide +,- and 3 degrees of data (2 thermopile pairs and a single thermopile sensor to determine if right side up compared to the other 4 sensors )Thoughts?Paul
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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. https://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.
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.
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 https://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
I may be mistaken, but I believe on the ATmega168 it takes more time to do an analog read than a digital one. So if you're really pressed for processing power and want to perform analog reads often, offloading the ADC to an external chip (very cheap!) might help.
Also, as Giles mentioned, the readings may be more resistant to noise if you convert it to digital closer to the source. But...that really shouldn't be a lot of code, they make chips designed to do exactly that.
If you wanted to have your themopiles a long way away from the autopilot then you might want to use an adc to reduce noise but you would have code a lot for it!!!
In general, it's a good idea to keep as much data as you can as long as you can so you can use the maximum amount of information in your filters. Analog has more information than digital, so it's better from that perspective. Also, the ATmega168 has loads of ADC pins, so doing the ADC conversion at the chip level is no computational hardship. In short, I don't see the advantage of converting to digital at the sensor level.
Replies
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. https://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.
I don't have an answer, but this seems to be the question being asked.
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
https://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
This has been particularly bugging me as I would like to be able to work on water.
Also, as Giles mentioned, the readings may be more resistant to noise if you convert it to digital closer to the source. But...that really shouldn't be a lot of code, they make chips designed to do exactly that.
Am I missing something?