KAP images of Parramatta High School- How to

Kite Aerial Photography
—A Design Brief —

The Cradle

Specifications for the cradle. Under remote radio control, it must allow for control of:

tilt from horizontal (horizon) to vertical (plan);
pan around the full 360°;
shutter release, reliably on demand.

More details below

All the above must be achieved with a reliable and robust construction which will withstand the considerable buffeting under a skittish kite and the pressure of a strong wind.
As well, it must be light enough to allow easy lifting under the kite.
Field repairs, if needed, should not be out of the question. The camera should be easily removable (for, among other things, replacement of batteries.)

Solution
The standard RC servo provides 90° of rotation - perfect for the tilt axis, from horizontal to vertical.

The pan axis, however, is a little more troublesome. In order to provide full coverage of the horizon, the rig must be able to pan through a full 360°. The servo can be geared up 4:1 to do this (as attempted last time) but this placed an unacceptable strain on the servo, and makes the movement much too fast and difficult to control.

Modifying the servo to rotate continuously.
This is suprisingly simple... very easy and effective.

This is the final drive spur gear from a typical servo. Arrowed is the lug which prevents the gear from rotating too far.
Its a simple matter to remove this lug with a sharp knife.

When the servo is reassembled, remove the short nylon piece which connects that gear (at left) to the feedback potentiometer in the servo.

This allows the servo to continuously rotate, without feedback pulses preventing the signal and stopping the rotation.

Click here for more details on constructing the cradle.

Return to Design Brief page 1.
Return to the camera modification page.