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bubblehead
03-14-2007, 01:44 PM
My son has expressed an interest in trying aerial kite photography.· We've found lots of information online.

Most people use radio control systems to control their camera gear.· We already have the RC gear, so that is what we'll use at first.· But we got to wondering if there was another way to control the camera·rig.· An more specifically,·a way to send to use the kite string itself.· Were not going to use wire, so it can't be an electrical signal.· Maybe, tugging on the string in some kind of pattern, or vibrating the string?· We thought the wind blowing across the string would overwhelm any 'signal'.· Spread spectrum/wideband techniques to deal with the noise?· We'd probably·use·SX chips and/or BS2's for the airborne package to decode the signals and drive the camera.

This is a pretty diverse group of smart people, so I thought I'd see if anyone had any ideas?

Paul Baker
03-15-2007, 01:02 AM
Ah, come on, your not interested in repeating Ben Franklin's experiments? http://forums.parallax.com/images/smilies/devil.gif

Seriously though, Im imaginging your not really interested in downloading image data in flight, that you'll off-load after you have retrieved the kite, and you are mainly interested in triggering the taking of pictures. You might be able to use an IR transmitter/receiver for this especially since the reciever will be pointing towards the ground and would be less blinded by the sun.

If you are really keen on the whole vibrating string·thing, the signal to noise ratio will be greater in the transverse direction, IOW vibrating the string in the direction perpendicular to the air flow will have less of and effect by the air flow and will be less damped by the action of the air flow as well.

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

Post Edited (Paul Baker (Parallax)) : 3/14/2007 7:32:19 PM GMT

Beau Schwabe (Parallax)
03-15-2007, 01:36 AM
bubblehead,

How long is the kite string? My concern would be propagation delay not to mention reflections. I think it would be relatively easy to "tune out" most of the noise with a decent band pass filter if you choose a high enough carrier frequency. <-- I have no idea what that would be, but I would raise it at least an order or two of magnitude over the noise floor. I would think that most of the wind interference would be relatively low frequency.

Interesting·TIN CAN TELEPHONE concept!

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Beau Schwabe (mailto:bschwabe@parallax.com)

IC Layout Engineer
Parallax, Inc.

PAR
03-15-2007, 01:50 AM
bubblehead said...
My son has expressed an interest in trying aerial kite photography.· We've found lots of information online.

Most people use radio control systems to control their camera gear.· We already have the RC gear, so that is what we'll use at first.· But we got to wondering if there was another way to control the camera·rig.· ...[signalling via the kite string...] We'd probably·use·SX chips and/or BS2's for the airborne package to decode the signals and drive the camera.
What specific control do you want to have over the kite/camera/photography ?

Why would the RC gear not allow that kind of control ? (I.e., whether or not you integrate the RC gear with a·microcontroller and actuators that directly control the photography?)· Is the challenge for you specifically in how to use a kite string as a signalling channel ? Or, is the challenge to use other (than RC)·forms of·remote operation and perhaps two-way communications (for data/intelligence gathering and processing)?

Dumb camera, or smart?·Lots of (remote controllable) access to your camera's "smarts", or is it all manual ?

PAR


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Bean
03-15-2007, 05:16 AM
Aside from the noise I would think the wind would have a dampening effect on any vibrations ?
You'll have to try some experiments and let us know.

[edit] oops, I didn't see Paul's post, he already mentioned it...

Bean.

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bubblehead
03-16-2007, 04:51 AM
Paul, You are right that it wouldn't be for downloading images, just for control of the camera. I've seen spring loaded catches that can be used to drop parachutes and things when you tug on the kite string. So, I imagine that something similar could be adapted to send control signals.

PAR, An RC system would provide all the control we need--pan,tilt,take picture. My son and I were just brainstorming alternatives.