Lake-bed scientific research photography

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Lake-bed scientific research photography
« on: 19 / June / 2013, 05:35:26 »
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Hello, my task is to take photos over a very long time (2-3 months) of a lake-bed that has some interesting features. The camera would take one picture every 6 hours minimum. Currently the Canon G12 is being looked into as it's CHDK compatible and takes great pictures. This is for academia research and not a commercial project.

I cannot find any information about the camera's (Canon G12) power consumption and battery capacity, for some reason this data seems to be taboo. I need to know if the camera's battery will suffice, if not I will probably need to build some additional circuitry with an external battery. The external battery would not be an OEM part, so I need to know if the Canon cameras can run on non-OEM battery or run while charging (with the DC plug).

Re: Lake-bed scientific research photography
« Reply #1 on: 19 / June / 2013, 06:59:15 »
« Last Edit: 19 / June / 2013, 07:01:13 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

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Offline ahull

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Re: Lake-bed scientific research photography
« Reply #2 on: 19 / June / 2013, 08:29:58 »
I think you will need the Canon ACK-DC50 for the G12 (or an after market clone thereof). You can then power the dummy battery from this with a external DC source (a large lead acid battery for example) regulated to the correct voltage (that link suggests DC 7.4V 2A, but check this carefully to avoid nasty and expensive smoke), and all packaged up in such a way as to protect everything from the environment of course.

If the standard NB-7L 1500mAh Battery for the Canon  G12 does give you 24hrs, then you would need a battery of more than 60 times this capacity to shoot for 2 months. A car battery looks like the most likely candidate as these can have capacities >120Ah which would from my quick back of an envelope calculation last about 80 days. 

You will of course keep us posted with the results  :D
« Last Edit: 19 / June / 2013, 08:41:25 by ahull »

Re: Lake-bed scientific research photography
« Reply #3 on: 19 / June / 2013, 13:57:59 »
A car battery looks like the most likely candidate as these can have capacities >120Ah which would from my quick back of an envelope calculation last about 80 days. 

Well, I can tell you I recently completed a number of one-month-long  time-lapses using a Canon A620 that shot for just eight hours a day and the LCD screen (not just the backlight) was powered-down for the rest of the time.
Nevertheless, using a 12AH sealed lead-acid battery I still had to change it every five days.
It is not advised to use more than 70% of the batteries amp-hour capacity.
For the G12 you would need to obtain a dummy battery, probably by purchasing the ACK-DC50 AC adapter.
At least for the G12 you can turn off the LCD screen.

In addition, the camera may stop for unknown reasons or unexpected 'events' may occur so a frequent visit is essential.


David


Re: Lake-bed scientific research photography
« Reply #4 on: 19 / June / 2013, 14:22:43 »
In addition, the camera may stop for unknown reasons or unexpected 'events' may occur so a frequent visit is essential.
That's why the ultimate intervalometer can reset the camera on a daily basis.  Not 100% guaranteed but certainly a good step for improving reliability.
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Lake-bed scientific research photography
« Reply #5 on: 19 / June / 2013, 14:37:22 »
That's why the ultimate intervalometer can reset the camera on a daily basis.

Sure, but by "unexpected events" I am not referring to the camera or CHDK.

I am referring to the "unknown unknowns".

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Offline reyalp

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Re: Lake-bed scientific research photography
« Reply #6 on: 19 / June / 2013, 16:17:40 »
For a 6 hour interval, it might be worth some external device to power the camera on / off as required instead of running it all the time. This could either be done by a servo, or by wiring the power switch into your controller. In this configuration, the external battery requirements should be very modest and some of the other potential reliability issues would be mitigated.

You might be able to use the internal battery in this scenario, but it would be advisable to cut the external power source a few seconds after the normal shut down is attempted, so the camera will actually get rebooted even if it's hung. A normal shutdown using the power switch or scripting should be attempted first though, because cutting the power can corrupt the file system.
Don't forget what the H stands for.

Re: Lake-bed scientific research photography
« Reply #7 on: 19 / June / 2013, 18:13:44 »
For a 6 hour interval, it might be worth some external device to power the camera on / off as required

I have such a setup (on my kitchen table) at present.

For some reason, after turning off it turns on again about ten seconds later.

Just an electronics problem .........



Re: Lake-bed scientific research photography
« Reply #8 on: 03 / July / 2013, 04:31:17 »
Thanks for the information. The best solution, with this camera, would probably be external control as reyalp said. Some ATtiny and a power-MOS. The ATtiny in sleep mode consumes less than 2uA which is quite good.

From the links waterwingz posted, and I take the power consumption of the G12 is similar to some extent, with some margin I'd evaluate the power of one picture at 1A for 10 seconds at whatever voltage the battery is. Similarly to the external flash (which has yet to be found/made) I'd evaluate a hefty 60W for 10 seconds with a 12V lead/acid battery, although a LED flash will very probably be used and would consume a fraction of that.

So the total power consumption, assuming everything eats 12V (some high-efficiency switching regulators needed), would be:
  • 24h*30day*3months=2160 hours total runtime
  • 24/6pictures*30days*3monts=540 pictures over the 3 months
  • 540pictures*1A*10secods*1h/3600seconds=1.5Ah for pictures
  • 540pictures*60W/12V*10secods*1h/3600seconds=7.5Ah for the flash
  • 2160hours*2uA=4.32mAh for the MCU

Total: 9Ah.

I've got some 12Ah, 12V lead-acid batteries and I have yet to see the consumption of the switching regulators, but it seems manageable... what do you think?

Re: Lake-bed scientific research photography
« Reply #9 on: 03 / July / 2013, 08:10:50 »
From the links waterwingz posted, and I take the power consumption of the G12 is similar to some extent, with some margin I'd evaluate the power of one picture at 1A for 10 seconds at whatever voltage the battery is.
This will certainly give you a conservative estimate.  For example,  when shooting,  my A1200 draws about 600 mA at 3V - that's 1.8Watts.   At 12V,  1,8 watts  means the camera will only draw 0.15A. Throw in DC-DC converter efficiency and you are still below .2A

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Similarly to the external flash (which has yet to be found/made) I'd evaluate a hefty 60W for 10 seconds with a 12V lead/acid battery, although a LED flash will very probably be used and would consume a fraction of that.
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.

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I've got some 12Ah, 12V lead-acid batteries and I have yet to see the consumption of the switching regulators, but it seems manageable... what do you think?
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.
Ported :   A1200    SD940   G10    Powershot N    G16

 

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