Firstly a big thank you waterwingz and reyalp for all the help you've given me with this project so far.
Well I've done some field tests with the setup below. I haven't actually taken it underwater yet, simply because I haven't visited an appropriate location yet (so I didn't bother waterproofing the trigger). Basically it's just a switch that connects 8 volts (from two li-ion cells) to the two solenoids which are attached to the mount using the same screw that threads into the camera's plastic tripod mount (not a good idea really). I kind of built it in a hurry since I left it to the day before the trip. There's also a 400mm piece of right-angle aluminium that I used to mount them further apart.
(that's the only photo I could find of it; it's now been completely dismantled)
I have a few anaglyphs uploaded
hereAs an FYI, if you were using a conventional USB remote, that's what the TwoPush switch setting does for you.
Thanks for that tip, otherwise I probably would have spent hours/days programming a micro and modifying CHDK code and wouldn't have got the setup done in time for the trip.
Anyway, now comes the next phase. I don't really like the largeish solenoids hanging off the cameras, I think it would be much better if I had a somewhat more wirless remote with a reciever inside the battery compartment. I'm not exactly sure how I'm going to do this, but I have a few ideas under my sleeve including amplified hall-effect sensors and maybe band pass filters, or some sort of receiver that works on a UHF or SHF
ISM band (yes I know that won't work underwater, if I do this the hall-effect sensors and solenoids will still be usable).
I have a question about the SD card interface though. As the camera doesn't use UHS-I write speeds, it uses
One-Bit SD Bus Mode right? There is an unused interrupt pin; is it possible that the camera hardware is capable of communicating with this pin, and that (with a bit of work maybe) CHDK could allow me to send or receive data from this pin? Or if there's another unused pin that may work instead? Just an idea, would make it easier rather than have to connect sensors in the SD card to the temp input pin (and if it can output, I could have the cameras in a wireless master/slave configuration).
