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D20's, hall effect sensors and stereo-photography

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Offline reyalp

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Re: D20's, hall effect sensors and stereo-photography
« Reply #20 on: 13 / January / 2014, 17:28:48 »
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the hall-effect-sensor itself is used to make a sync signal pass a waterproof case, right? But why is it connected to the sd-card? To power it only or is the sync signal fed into the camera this way? Thanks a lot for helping someone at a completely lower level! :-)
Connection to the SD card is only for power. The sync signal uses the battery temperature sensor input. If you don't need the door sealed, you don't need to use a hall sensor. See this thread for earlier discussion http://chdk.setepontos.com/index.php?topic=10385.0
Don't forget what the H stands for.

Re: D20's, hall effect sensors and stereo-photography
« Reply #21 on: 13 / January / 2014, 19:19:36 »
Aaaaah! Okay, I did not get it that these freds belong together in some way. Okay, I'll post my questions in the other thread. :-)

Re: D20's, hall effect sensors and stereo-photography
« Reply #22 on: 27 / January / 2014, 13:18:56 »
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 here


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As 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).


Re: D20's, hall effect sensors and stereo-photography
« Reply #23 on: 27 / January / 2014, 13:33:45 »
I have a few anaglyphs uploaded here


Good depth and carefully positioned stereo window.

There is something not quite right with last image, the clump of foliage at middle left.



Re: D20's, hall effect sensors and stereo-photography
« Reply #24 on: 27 / January / 2014, 13:59:12 »
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There is something not quite right with last image, the clump of foliage at middle left.
I'm not quite sure what happened there, I took two stereo images of that tree and they both had that same problem. Perhaps the trigger was behaving badly at that time and triggered one camera before the other on both occasions (as it did quite a few other times on the trip due to a bad connection with the batteries)

BTW, the location was the 'Valley of the Giants' treetop walk

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Offline reyalp

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Re: D20's, hall effect sensors and stereo-photography
« Reply #25 on: 27 / January / 2014, 16:39:54 »
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?
I'm no expert on SD, but I don't think that follows. From the wikipedia page, it appears that 4 bit mode pre-dates UHS by a long time (since it was part of the MMC and original SD standards), it just becomes mandatory for UHS. The cards all start in 1 bit mode, and then the controller negotiates.

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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?
Leaving aside whether this pin is actually unused, I don't recall ever coming across anything related to controlling the card at this level. On the other hand, I haven't gone looking for it...
Don't forget what the H stands for.

 

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