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CHDK in the stratosphere

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Offline fudgey

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Re: CHDK in the stratosphere
« Reply #10 on: 03 / January / 2009, 09:05:11 »
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I believe the camera will run off just USB power. 

It's highly likely that it will not work from USB power without exceeding the 500 mA USB spec, not even if you step down to whatever your battery voltage is using a high-efficiency switching regulator. Even if you never use zoom or flash during your flights, you'll have a hard time starting up the camera and shutting it down safely before landing because the lens motors require lots of current.

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Offline fbonomi

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Re: CHDK in the stratosphere
« Reply #11 on: 03 / January / 2009, 09:27:11 »
I don't think the camera runs at all from the USB power.

Other cameras (such as the a570) have an external supply jack that could be used. I used it with a wall adaptor or with a motorbike battery for ver long timlapses...

Anyway, we must consider that we are using the USB 5v line as a "data" line to signal to the camera, so we couldn't anyway turn it off without turning off the whole system :-)

Re: CHDK in the stratosphere
« Reply #12 on: 03 / January / 2009, 09:38:21 »
maybe there's even other things in the rig keeping the camera warm? And it's so much colder that one just can't expect extrapolate linearly that far with confidence.

There is.   If you look here http://dcshrum.ais.fsu.edu/images/IMG_0022.jpg you can see we have a voltage regulator attached to a heat sync.  That was a result of having a 14 volt li-poly battery and a 12 volt motherboard.  The heat sync does get pretty hot.  I never measured it but I'd say after an hour you do not want to touch it.

Curious, has anyone ever wired an external battery?  It would be more efficient to use a voltage regulator off the larger battery.  Actually now that I think about it you could just wire a 5 volt regulator to the USB cable.  But then you would not be able to send signals to the camera.  I believe the camera will run off just USB power. 

I used the AC Adapter Kit ACK-DC10 (same for my TX-1s as your SD1100). Cut the cable from the Vdc output side of the adapter, attached connectors and used larger capacity batteries.

Used something like this I found at Radio Shack:

Horizon Hobby: Connector Set 7.2V by Tamiya America, Inc (TAM50106)

By putting matching connectors on the ac adapter as well, I can either use power off the wall or larger battery packs depending on the situation.

And, BTW, Great Pix!!!

HTH,
« Last Edit: 03 / January / 2009, 09:46:02 by cybercom »
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Offline fudgey

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Re: CHDK in the stratosphere
« Reply #13 on: 03 / January / 2009, 10:13:32 »


Re: CHDK in the stratosphere
« Reply #14 on: 03 / January / 2009, 10:36:19 »
I believe the camera will run off just USB power. 

The USB V+ signal is not power, it is a logic signal that turns-on some transistors.
The output from the transistors goes to the DIGIC processor.

The USB signal can be very low power, far lower than some of the USB remote switch circuits pblished.

Re: CHDK in the stratosphere
« Reply #15 on: 03 / January / 2009, 11:09:36 »
Ahhhh...  I see.  But the output off the adapter is 7.2 volts?  I would have guessed 3.7 volts as the battery is a single cell lithium. 

That would actually work spot on if its 7.2 volts because the radio is 7.2 volts as well.

I was planning on getting one of these: Adjustable step down switching voltage regulator

Francesco,

When the camera shut off was it due to the battery temperature or a result of the temperature of the CCD?  I'd guess the chemical reaction in the battery sort of slows or stops at very cold temperatures.  With a 14 volt battery, even with a good voltage drop you'd still be able to produce the 7.2 volts required.  It would be reasonably easy to wire up.

Re: CHDK in the stratosphere
« Reply #16 on: 03 / January / 2009, 11:38:36 »
  But the output off the adapter is 7.2 volts? 

He does not say that.

That is how the connectors are described but that must be a standard for RC model cars.

You can use the connectors on lower and far higher voltages than 7.2V.

If your heatsink is getting that hot you are wasting a lot of energy.
Of course, it helps keep the equipment warm.
If cold was not a problem. I would use the far more efficient commercial switching regulators.
In fact, despite the low value of the GBP against the USD, I intend  buying one from the US.

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Offline fbonomi

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Re: CHDK in the stratosphere
« Reply #17 on: 03 / January / 2009, 19:19:46 »
I have posted here: Temperature as measured by the camera an article about the camera's temperature and voltage data that were logged during the flight.

They are rather interesting, I think..


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Offline reyalp

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Re: CHDK in the stratosphere
« Reply #18 on: 03 / January / 2009, 19:36:15 »
Don't forget what the H stands for.

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Offline PhyrePhoX

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Re: CHDK in the stratosphere
« Reply #19 on: 05 / January / 2009, 13:29:14 »
impressive, chdk in space again. we should consider creating a wiki page about things that CHDK can do that are completely unique in the world of photography (for example the temperature stuff) or at least in the world of the "cheap photography" :D

 

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