Why won't my AC adapter work with digital camera?

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wizguru
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Why won't my AC adapter work with digital camera?

Post by wizguru » Mon Nov 30, 2009 7:07 pm

My Kodak C743 digital camera uses KAA2HR dual 1.2V AA battery pack (lid conductor connects pos. of one AA to neg. of other in series for 2.4V for camera). Also works with dual 1.5V alkaline AA cells. I built AC adapter using LM317 adjustable regulator IC, voltage adjustable 2.4V-3.2V. To mimic battery pack, I used two plastic tubes of AA diameter and simulated the pos. terminal at one end and neg. at other end. However, camera won't turn On for any voltage from my AC adapter. I know that a connection is being made because my DMV indicates a capacitor charging on 2Mohm scale. Lid has no affect because if I press down cells with metal tool across cells and lid fully open, camera also works. Does camera have a built-in sensing circuit that senses battery internal impedance and auto shuts Off when not detected? How can I fix this?

Robert Reed
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Re: Why won't my AC adapter work with digital came

Post by Robert Reed » Mon Nov 30, 2009 8:52 pm

This is a shot in the dark and I would not advise it without further investigation. I had a similar problem on one of my cell phones in trying to construct a charger for it. Had as nice a DC as you would ever want but no-go. A little detective work revealed that the commercial charger for this puts out only AC and the phones input was capacitively coupled to a bridge rectifier internally. Redesigned the charger with a simple astable circuit at 60Hz and now it works like a champ.

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CeaSaR
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Re: Why won't my AC adapter work with digital camera?

Post by CeaSaR » Mon Nov 30, 2009 9:34 pm

What is the current rating of your adapter? Can your "homemade adapter" actually supply enough current to run the camera?
I ask this as I found out that an external battery pack I had made for my camcorder couldn't run it even though I was using
D cells and the correct voltage. I ended up needing 2 or more packs in parallel just to get the thing to start up.

So, with AA's you'd probably be running between 300 - 600 mA for the camera. Make sure you can easily supply that much
and probably up to 1000 mA. Also, make sure you have the smoothest DC you can get out of your adapter. Excess ripple
may cause problems for the camera.

To check what current capacity you can supply, look at your transformer rating. It needs to put out at least the minimum
stated above (600mA), preferably twice as much.

Good luck,

CeaSaR
Hey, what do I know?

wizguru
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Re: Why won't my AC adapter work with digital camera?

Post by wizguru » Wed Dec 02, 2009 1:26 pm

Thanks for responses.

My adapter puts out 500ma DC. Although 500ma would seem to me to be more than adequate, you might be right, so I will try to find a 1000ma DC adapter. I have a 2200uf capacitor across LM317 output, as well as a 0.1uf poly for RF decoupling, so ripple should be very small.

In the cellphone case, the AC adapter is required because the cellphone picks off the 60 Hz to be used for its internal timing purposes. This is not the case here.

Thanks. John

wizguru
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Re: Why won't my AC adapter work with digital camera?

Post by wizguru » Sun Dec 06, 2009 8:25 pm

I got it to work, but not exactly as expected.

I changed by 500ma adapter for a 1250ma adapter, then adjusted it to 3.2V, and it still did not work. However, when I adjusted it to 3.4V (after changing the LM317 pot) it worked fine. So I left it at 3.5V. This is strange because my AA alkaline batteries were working down to about 1.45V each, 2.90V total. Hmmm.

I use this camera to do a lot of eBay images, and I took on this project because I was sick and tired of chasing down, charging, buying and replacing batteries.

Thanks for the advice. John

Robert Reed
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Re: Why won't my AC adapter work with digital came

Post by Robert Reed » Mon Dec 07, 2009 12:26 pm

Wig
I experienced the same frustration that you were going thru and so built my own AC power pack. Although I use a Fuji that requires 5.0 VDC supply. One word of caution here- I designed a built in crowbar circuit that trips the supply at 5.4 VDC. I know of one unfortunate soul that did the same as us. Then one day, the supply failed and poof went the camera. I guess it all boils down to how much you paid for the camera.

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