It's been awhile since I posted any progress in the other thread:
http://chdk.setepontos.com/index.php?topic=10385.0 due to school commitments so I thought I might need to start a new thread.
I have recently obtained a second (and previously a first) D20 waterproof camera, with plans for underwater stereo-photography. Of course this also presents the problem of syncing the cams without compromising the waterproof aspect of them. I don't want to risk a DIY seal solution; the doors must both be closed.
I've come up with four ideas that may work; if anyone has any others they would be appreciated aswell.
1. Use a Hall-Effect sensor (with an external electromagnet to trigger it). It will be permanently attached to the back of the battery. As Hall effect sensors draw a continuous current of about 15mA, it will drain the battery over time. I have tested an unamplified hall-effect sensor attached straight to the battery and temp-input, and it measures a magnetic field change without too much trouble using
print(peek(0xc090004a,2))2. Same as above, except that I open up the cameras and put the sensor inside (I got them second hand anyway so no warranty to void) and power the sensor from somewhere that loses power when the cam is off, so no need to worry about battery drain while off. Has anyone else ever opened up a D20? (maybe to try to fix one?)
3. Use an inductive coil pickup (rectified to dc) attached to the temp-input. Another external coil will send out a pulse or two which will be picked up by the internal one. A small Zener diode will protect the voltage from going too high. I'm not sure whether or not the image stabilizer will be interrupted by the pulse though.
4. Use a lightening-capture motion sensing script and a flash. However I plan on using this rig mainly to take photos in daylight settings where there's moving subjects and no need for a flash, so not sure how this would work. Also I don't imagine they would be synchronized that well.
I'm thinking the hall effect sensor sound the most pleasing, the sensors (obtained out of old floppy-disc drives) are only about 3x1.5x1.5mm in size and are quite versatile; mounting one on the battery or inside the camera will not be a problem. If anyone has any other ideas or suggestions they would be greatly appreciated too.
Also, in order to make it usable, I will need to modify the CHDK code somehow to monitor the A-D temp input for changes like it currently monitors the USB voltage input. Previous attempts at using scripts to read the temp-input were no where near fast enough to sync properly. If anyone could set me off in the right direction here with where to that would be great.