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Sam
Joined: 18 May 2008
Posts: 135
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 Posted: Thu Dec 17, 2009 9:33 am Post subject: Kind of off topic. Speed sensor needed. |
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The box would be the width of the runway, with the pilot striving to stay pretty much on the center line. Probably as low as 20 feet and as high as 100 feet - maybe 75.
On Thu, Dec 17, 2009 at 10:41 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
| Quote: | The use of radio to tie the ends of the system together
is quite practical. There are inexpensive, off the shelf
timers available with micro-second resolution/accuracy.
The proof of the pudding is in the sensor array.
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What is the size of the "box" that the aircraft must stay inside
and what height above the ground is the lower edge of that box?
I occurs to me that if you have a 100' wide by 100' high
box with lower edge at 100' agl, the number of sensors
required to cover that up-look area with any resolution
could be pretty big. Fortunately, they're cheap and easy
to build. So is the electronics for resolving the presence
of an airplane "shadow"
Bob . . .
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Sam Hoskins
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david.nelson(at)pobox.com
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| Posted: Fri Dec 18, 2009 3:26 pm Post subject: Kind of off topic. Speed sensor needed. |
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Hi Sam,
How about a Wii game console remote? These little remotes have a 3-axis
accelerometer, Bluetooth, and an IR camera all for the cost of about $40/ea.
They are durable and available at any Wal-Mart so replacements easy should they
ever get lost, damaged, etc.
There are several examples of interfacing these guys w/ PC's, also. In fact,
some scientific communities are using them instead of high dollar/special
purpose sensors:
http://www.wired.com/wiredscience/2009/12/wiimote-science/
Some more example usage and some Wii remote specs:
http://johnnylee.net/projects/wii/
More info on the remote can be found here:
http://en.wikipedia.org/wiki/Wii_Remote
What I was thinking was:
1) With the accelerometer, they can be accurately aimed straight up thus
ensuring that the distance between the two points is accurate regardless of the
height of the aircraft.
2) Provide a good IR source pointing up.
3) Place some reflective tape on the bottom of the aircraft in such a manner
that it won't affect the surface.
4) Do this on both ends of the runway, throw in some WiFi (to allow
communications and to synchronize the time) , some WiFi and Bluetooth enabled
laptops (Bluetooth dongles cost $20/ea), some programming (there are C, C# and
python libraries available for free), and I'd think you'd have a fairly
inexpensive setup assuming that equipment could be donated, borrowed, and/or
purchased as used.
Some testing would have to be done if a target could even be detected at 100'
AGL in strong daylight. Given that, everything else is doable.
One could go so far as to build dedicated enclosures using micro-ATX
motherboards with all the included components for very reasonable prices.
If you know of anybody with a Wii remote and a Linux based PC, have them look
into the "CWiid" package. It comes with a 'wmgui' demo program so that you, or
anybody else, can get a feel for how things work.
Regards,
/\/elson
Austin, TX
~~ Lately my memory seems to be like a steel trap .... without any spring. ~~
On Mon, 14 Dec 2009, Sam Hoskins wrote:
| Quote: | Aeroelectric listers,
We're looking for a bright idea. Preferably an inexpensive one.
The Sport Air Racing League, http://www.sportairrace.org/ is trying to develop an accurate and reliable way to time the speed of an aircraft zooming down a runway, at 50 feet or so. They are
looking for some kind of trigger that will start the clock at one end, and stop it at the far end.
We don't really want to erect pylons to fly through to break a beam, that would be unwieldy. Some of the guys have looked at airborne systems, such as GPS tracking, but it's not accurate
enough.
The SARL group is having a hard time coming up with something. Anybody have any thoughts how we might accomplish this?
Thanks for any ideas.
Sam Hoskins
Race 22!
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