External power supply using “fake batteries”

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External power supply using “fake batteries”

Postby kusnick » 19 Feb 2011, 12:41

Hello folks. One of the most challenging problems in using “cheap” cameras is the lack of some resources that could be useful for our bookscanner purposes. One of these features is the possibility to use an external power supply. This is particularly problematic when you need to be “ready to go” and just realize that your cameras must wait hours to be charged… or, what is not uncommon in our case, is to put the cameras through a heavy duty cycle. In this situation the batteries may discharge before work is done.

One might say that the solution is to have spare batteries. But practice has taught me that stopping the work to change one or both batteries is time consuming, due the necessity to remove the cameras from the rig and to set them up again.
Another thing to think about is the cost of spare batteries. In some cases a battery may cost almost the half price of the camera!
So I’m going to tell you about my experiences with two models of camera: the Olympus T100 and the Sony DSC-W320. I think that a similar trick is applicable to different cameras, what is important here is the principle involved, but each case must be carefully studied.

I started with two Sony DSC-W320 for bookscanning. After hundreds of pages I realized that I really need an external power supply… but without an external power connector, what to do? There wasn’t even a power supply available for this camera..
Well the obvious solution was to make one trying to match the cameras’ voltage and amperage needs. This is not a big deal to who is familiar with electronics (I’m just a weekend mad scientist). Anyway I’ll post the instructions to build a “stereo power supply” in a later post.

The real deal here is how to connect a cable inside the camera. The contacts are located deep inside; you can barely see them, much less connect the wires.
This is what a DSC-320 battery looks like.

DSN019.jpg (4.3 KiB) Viewed 9067 times

It provides around 3.7 volts and has three contact: “+” , “ – “ and a mysteries “ C “ thing, the central one. To provide a reliable contact we made simulacrum as you can see above:

fake batteries.jpg
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Using acrylic we made a piece with the same shape and size of the battery which fit perfectly inside the camera. The contacts were made using copper wires. A shielded cable was glued and to make external connections easily available.

You may notice a narrow and long “thing” inside the plastic stuff. It’s a chip… “A chip, WTH!!!” Calm down, I’ll explain it latter.

Here is my power supply and both bookscanner’s cameras ready with the fake batteries.
power supply.jpg
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As you can see I needed to remove the battery / memory card cover to allow the passage of the cable. Some mutilation was inevitable here…

Now, lets talk about the chip stuff. During the tests I notice that even when the fake battery was well connected with the internal contacts “+” and “ - “ and using the right voltage the camera tuned on but few seconds after it showed a message "for use with compatible battery only" and shuts down. Bad girl!

To make a long story short, the problem was the “C” terminal. It performs a kind of communication between the camera and the battery. The solution was to trick the camera to “think” that a real battery was connected. To do this, disassemble the battery and remove the small circuitry that is connected to the contacts.
schip.jpg (59.21 KiB) Viewed 9067 times

So this circuit was inserted in a channel made into the plastic fake battery. The (+) and ( - ) terminals were connected in parallel and the “C” terminal from the chip to the camera contact. By doing so the whole set worked fine!
working cameras.jpg
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For the Olympus T100 the procedure is almost the same, except for the fact that’s less demanding: you don’t need to disassemble the battery and use the inside chip, it is enough to make those fake batteries and connect the “+” and “-“ terminals.
Different models of cameras may require different approaches.

At this point you may say “That is so much work, why not just spend some more bucks and buy a better camera, with external power supply?” The answer is that I’m working with a team that aims to provide an affordable and reliable solution for digitalization in universities. The price of the cameras is a critical factor for budget when you are about to build almost a dozen bookscanners.

I want to thanks Dr. Gerson Kniphoff da Cruz from the Department of Physics of UEPG
(State University of Ponta Grossa, Paraná – Brazil) for he for provided the equipment and space to shape the plastic stuff, and Dr. Edson Armando Silva from the Department of History of the same institution for his enthusiasm (he wants do digitize the world).

Ah, before finish this post I must make one point clear; its important to remember that if you decide to make the same type of experiments do it a your own risk: batteries contains dangerous substances, so you should manipulate and dispose of it with caution. There is also a risk also to damage the cameras, after all we are dealing with experimental stuff here. Whatever! Be careful.

As soon as it is possible for me, I’ll post details about the constructions of the power supply and another important device for this type of camera: a mechanical trigger.

Marcos Kusnick
Ponta Grossa, PR, Brazil
working cameras.jpg
working cameras.jpg (99.72 KiB) Viewed 9067 times

Re: External power supply using “fake batteries”

Postby spamsickle » 19 Feb 2011, 14:10

Excellent. I hate batteries. HATE HATE HATE HATE HATE.

When absolutely necessary (i.e., my cell phone), I'll use rechargeable batteries. When that's not possible (i.e., my car's remote access control), I'll use disposable batteries. But I always hate them, and will always choose another option if one is available.

I don't think I have the skills to wire a unit that replaces even the 4 AA cells in my "no power adapter" camera, much less one that requires a "look at me, I'm compatible" chip, but it warms my heart to know that such people are out there. Thanks.
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