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Hi this is my first share.
Got a Canon A2400 power shot a month ago. Got the CHDK firmware working on it very happy with the results. If you haven't heard about CHDK it's really worth looking at. It enables you to access the raw power of the camera. You can get the functionalities you would usually find on a DSLR camera on to a cheap point n shoot camera.

The camera's battery is puny and had only enough juicy for maybe an hour. Not enough if you want to take time lapse shots. So saw a few hacks where you can replace the battery with a dummy one and connect it to a external power source. The same product is available from canon for a price of 70$!!! That's inane given that the camera itself costs just about 100$

So gave it a shot with what I had lying around at my home and this is what I came up with.

Cut a small piece of 5mm thickness acrylic sheet and sanded it down to the battery pack's size. Cut out a small PCB and etched out the terminals for the battery. Cut out some slots in the PCB corner so it would fit neatly in the camera. Used an old worn out soldering iron tip to carve out the groove for the wires in the acrylic piece.

Used a old laptop power adapter as the main power source. (Provides almost 3.5A @ 19V)
Hooked up a couple of 7805 regulators in parallel to get more current. Used the circuit from the following link.
Not the best idea to use linear regulators for stepping down 19V to 4.3V but that's all I had lying around. Gets petty hot after just a couple of shots. This circuit may work better with a lower voltage input source. But works for now.

The camera uses nominally 300mA when idle, but peaks up to 700mA while charging up the flash for a couple of seconds.

That's it for now let me know what you guys think. Will definitely need to a switching type regulator in the long term but this is all for now... :)
Peter Rowe's profile photoPaul Frederick's profile photoKelly Devine's profile photoA Kumar's profile photo
If you have any higher voltage regulators try putting them ahead of the 7805's to divide the load. 7812 would be ideal. 
A Kumar
I could do that I will still need a pair of 7812 one for each 7805. I even thought of using a couple of high wattage resistors to make a voltage divider but I will still end up dissipating lot of power unnecessarily. Thanks for the idea though I think I have a couple of 7809s lying around here somewhere.

But I still think it's high time I looked at switching regulators or hacking up an ATX power supply. 
+Bongo Lee Yeah, you're better off doing it "right" but if you had 7805's kicking around, I figured the odds are you may have other 78xx's laying around too. In which case you can fix this without having to buy anything else.
I like the dummy battery. Sometimes the things we knock up in five minutes turn out to be the best solution.
A Kumar
+Peter Rowe That did not take just 5 mins to do. :D
That took almost half a day to get the right size shape and fit. I just have a hacksaw and some scraps of sand paper. But it fits like a glove and the effort was worth it. 
Not the best collection of circuits I've ever seen.

This link almost has the schematic you need


You just have to swap R2 for a 5K variable potentiometer, then adjust it for the voltage you want.

But you said you're working with what you have so that has merit in itself. As you've noticed with a large differential between input, and output voltage linear regulators do make a lot of excess heat. Ideally you should drop the minimum voltage between your input, and output, which with a linear regulator I believe is something like 1.25 volts above output? Even using a 12 volt input as opposed to the 19V you have now would help you out though.
A Kumar
+Paul Frederick Thank you for that schematic. Makes more sense than the one I saw. Will give it a try next weekend.
I don't have any power transistors but I do have some power FETs z44 I think and LM 317s. Any idea if it will work out instead of the transistors?
+Bongo Lee
I don't think so. All pass transistor regulators I've seen always use bipolar transistors. Although I'm not sure, so maybe. Just because I've never seen something doesn't mean it doesn't exist. I still think FETs are more suited to current as opposed to voltage control.
We really enjoyed your project and shared it in our weekly ""Community Corner"" post at Adafruit! http://adafru.it/b101092 
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