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Lake-bed scientific research photography

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Re: Lake-bed scientific research photography
« Reply #10 on: 03 / July / 2013, 08:57:02 »
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I don't have any experience here other than thinking that my external flash batteries would be dead after only a few shots if the recharge power was 60W for the duration of the charge cycle.  You could probably get a better estimate based on the approximate time to charge the flash,  the number of charge cycles from fresh batteries and the amp-hour rating of the battery pack.
The flash is kind of a challenge, it has to be external and consume very little, but it doesn't have to be very powerful as the sediments will reflect light and if too intense it'll be like a picture of falling snow with a flash, that is useless. So the flash power has to be calibrated to what I need, which I don't know yet. As I said I will probably build a LED flash of some sort and drown it in some hot glue or something.

I'm guessing that you could probably just use the Ultimate intervalometer for a month with that size of a battery - so using your ATtiny should leave you lots of headroom.
I've looked at it and it's probably what I'm going to use.

I'm still a bit hesitant to acquire an expensive camera for the sole purpose to hack it so does what I want, but I guess I don't have a choice. A script would have to load preset settings each time it powers up for consistent pictures and wait for a signal on USB line from the MCU to take a picture (for additional future feature) according to the Wiki all this seems to be possible with CHDK.

Re: Lake-bed scientific research photography
« Reply #11 on: 03 / July / 2013, 14:29:32 »
The flash is kind of a challenge, it has to be external and consume very little, but it doesn't have to be very powerful as the sediments will reflect light and if too intense it'll be like a picture of falling snow with a flash, that is useless. So the flash power has to be calibrated to what I need, which I don't know yet. As I said I will probably build a LED flash of some sort and drown it in some hot glue or something.
Sounds like you are looking more at a "lamp" than at a "flash".  Experiment with intensity and camera ISO & Tv settings.  You can probably afford a very slow shutter speed as you are on a permanent mount ( aka tripod) and the lake bed is not likely to move much during the exposure.   This will let you limit the lamp intensity needed and thus the power.

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I'm still a bit hesitant to acquire an expensive camera for the sole purpose to hack it so does what I want, but I guess I don't have a choice.
You lost me here.  Is the issue buying an expensive camera ( a $100 Canon P&S is not really expensive) ?  Or that you have to add a hack to perform an obscure function that the general public does not want or need and thus is not commercially available?

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A script would have to load preset settings each time it powers up for consistent pictures and wait for a signal on USB line from the MCU to take a picture (for additional future feature) according to the Wiki all this seems to be possible with CHDK.
All very possible and easy to implement.
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline ahull

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Re: Lake-bed scientific research photography
« Reply #12 on: 03 / July / 2013, 15:07:59 »
Quote from: Nurgak
I'm still a bit hesitant to acquire an expensive camera

If the cost is a genuine concern, you might consider a second hand camera from ebay or wherever, although as Waterwingz pointed out, in the great scheme of things, even a new P&S Canon is not *that* expensive (and has the advantage of a warranty).

Canon also have their own outlet on ebay here,  and affiliated stores here where there are often good deals to be had on refurbished items (generally with warranty).   
« Last Edit: 03 / July / 2013, 15:16:23 by ahull »

Re: Lake-bed scientific research photography
« Reply #13 on: 27 / August / 2013, 10:45:00 »
I finally bought the camera and I'm playing with it.

The microcontroller idea won't work unless I either add a servo that pushes the On/Off button or I open the camera and hard wire the On/Off button to my microcontroller to turn it on. Both solutions are shoddy IMO.

So now I'm looking for a way to lower the power consumption of the camera as much as possible during idle time so that the camera could take care of this mission by itself.

Currently is draws 2W without any optimisations. I can lower it to 0.8W with the display off. I read from multiple threads that you can "assign" a sleep mode to the print button and that can lower the power consumption even further, I wasn't able to find any documentation on the how-to though.

With my 12V, 12Ah camera I can realistically get about 100Wh, if that needs to last 3 months I need an average power consumption of 100Wh/(3*30*24)h=0.046W. Is that even possible with currently known methods?


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Offline ahull

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Re: Lake-bed scientific research photography
« Reply #14 on: 27 / August / 2013, 11:45:32 »
You may be able to do this without altering the camera. Most Canon cameras come on if you hold down the power button at the same time as you power on the external power source. 

Therefore if you run the camera from an external battery, you can control the camera power on and off with a simple switch ( a relay or MOSFET) connected to your micro-contoller. I am working on a similar idea in this thread.

You can hold down the power button with a bit of heavy duty tape, or a suitably crafted clamp. Keeping it pressed doesn't affect the camera operating in the normal fashion. There are a number of other suggestions in the thread.


« Last Edit: 27 / August / 2013, 11:48:17 by ahull »

Re: Lake-bed scientific research photography
« Reply #15 on: 27 / August / 2013, 12:10:39 »
I read from multiple threads that you can "assign" a sleep mode to the print button and that can lower the power consumption even further, I wasn't able to find any documentation on the how-to though.
Take a look at this : http://chdk.wikia.com/wiki/Ultimate_Intervalometer
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline reyalp

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Re: Lake-bed scientific research photography
« Reply #16 on: 27 / August / 2013, 13:10:01 »
With my 12V, 12Ah camera I can realistically get about 100Wh, if that needs to last 3 months I need an average power consumption of 100Wh/(3*30*24)h=0.046W. Is that even possible with currently known methods?
Almost certainly not. See http://chdk.setepontos.com/index.php?topic=9049.msg97241#msg97241 lowest measured consumption was 50mA in sleep mode. At 3.4 V that's 0.17 W. It's *extremely* unlikely that a software hack could cut this by a factor of ~4.

There are some other power measurement linked from that thread.

Also see http://chdk.setepontos.com/index.php?topic=10551.0 for more options for controlling the screen. This allows you to turn the screen off completely in playback mode, which may save slightly more power than backlight off (though I would guess that's not better than "sleep", if available)
Don't forget what the H stands for.

Re: Lake-bed scientific research photography
« Reply #17 on: 27 / August / 2013, 15:47:36 »
if that needs to last 3 months

Today is Tuesday.
That means time to swap the lead-acid battery on my time-lapse rig that has been running for five months.
It also means that I can clean the enclosure window, ensure the camera is still saving images, no foliage, creatures or other unknowns have affected the rig, etc.

A lot of 'stuff' can happen in three months.


David


Re: Lake-bed scientific research photography
« Reply #18 on: 29 / August / 2013, 09:10:53 »
You can hold down the power button with a bit of heavy duty tape, or a suitably crafted clamp. Keeping it pressed doesn't affect the camera operating in the normal fashion. There are a number of other suggestions in the thread.
Yep, that's exactly what I needed. I have access to a 3D printer and I have to make a mount for it anyway, so I can include a suitably crafted clamp.

I was also able to power the camera with 5V instead of the 7.4V, since it's the same as the MCU I'm planning to use I need only one switch-type regulator.

if that needs to last 3 months

Today is Tuesday.
That means time to swap the lead-acid battery on my time-lapse rig that has been running for five months.
It also means that I can clean the enclosure window, ensure the camera is still saving images, no foliage, creatures or other unknowns have affected the rig, etc.

A lot of 'stuff' can happen in three months.


David
I think it's not supposed to move during all this time and I'm not qualified to dive 300m for maintenance...

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Offline reyalp

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Re: Lake-bed scientific research photography
« Reply #19 on: 29 / August / 2013, 14:02:57 »
I think it's not supposed to move during all this time and I'm not qualified to dive 300m for maintenance...
If this is serious, I think you need to carefully consider whether a Canon P&S with CHDK is really an appropriate solution for your application. If the camera hangs 10 days into your project, what are the consequences? How do those consequences compare to the costs of a properly engineered solution designed for your target environment?

Canon P&S are mostly decent quality, but they aren't engineered for months of continuous operation or mission critical reliability. If the camera crashes, the consumer just has to press the power button again, or at worst take the battery out. On top of that, CHDK is a hack. It operates by poking the guts of a complex, completely undocumented system, using techniques that were often discovered through trial and error with limited understanding.

At a minimum, you need to arrange for the ability to hard reboot the camera by cutting the power, and then re-applying it with the power button pressed. You could still end up with a corrupted SD card, which would require physical access to the camera to resolve.

I'm not trying to discourage you from using CHDK. I love to see all the weird and wonderful things people do with it. It might work fine. However, it is important to have realistic expectations.
Don't forget what the H stands for.

 

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