Stefan blogs IT

DIY Canon AC-Adapter

November 30th, 2011 Posted in Photography

I’m a big fan of time-lapse projects. But there always are 2 limitations. Memory Card space and Battery life. The memory card space is easy to overcome. Connect your DSLR with laptop/pc/mac and store the images there, or buy a bigger memory card. 16GB can go a long way with medium-sized JPG’s. Battery life is the main problem in my eyes. Using a Battery grip, 2 Canon batteries only go for about 6-10h. Setting the review-time to 0s can save a load of battery power, but it still doesn’t extend the battery life long enough.
I have tried putting 6 Eneloop AA batteries in the grip. This babies kept the camera running for about 25hours. A serious improvement, and great for mobile time-lapses.

I wanted to be able to plug my camera in a power outlet, so it could virtually run forever. Canon has such an AC-Adapter. The ACK-DC20. But at a price of £76 I had no intention of buying it. In stead, I built one myself with things I had in my ‘storage’ and spent less than 2euro. From scratch you’d be able to build this for about 15-20eur.

You will need:

• A 12V AC-DC adapter with an output power of 1 Ampere (1000mA)
• An old Canon battery
• Some soldering equipment
• A piece of PCB
• wires
• An LM7808
• Two 1ouF 16V Capacitors
• A female adapter-plug

This ‘tutorial’ will guide you building the AC-Adapter for a Canon 400D, but since all canon’s have the same 7.4V batteries this will work with any other Canon DSLR and probably any other brand of DSLR.

Step 1: The battery

The first thing you have to do is open up an old Canon battery. I had a few old ones laying around which couldn’t keep a decent charge. Cut the battery open along the lines. Be careful that you don’t cut too deep into the battery inside. start with the corners and gently cut deeper till it opens.
You’ll have something like this:

Take the batteries out and cut them from the separator. Keep the separator containing the metal plates. We’ll need that upon assembly.

Step 2: The scheme

The soldering is fairly straightforward. I am using an LM7808 Voltage regulator. This chip keeps a constant DC voltage between 7.9 and 8.1V. This is perfect for the camera as it can take up to 8.1V as you can see in the Image. The green circle highlights the cable-gutter on the camera.

This voltage regulator costs less than 1 Euro and can power up to 2Amps, The camera doesn’t use more than 1Amp so it doesn’t need any cooling.

Pin layout of the LM7808:

The schematics:

As you can see it’s fairly straightforward. The 12V gets connected to the IN pin. 1 capacitor is placed between the IN and GND for ripple-deduction which might come from the adapter. Another capacitor is placed between the OUT and GND for a stable voltage. This is not mandatory but I did it anyway.

Step 3: The soldering

1: Solder the female adapter-plug onto a piece of wire. This can be a short or long wire, as you please. The female plug you see on the right.

2: Take a small piece of PCB which will fit inside the battery shell and solder the LM7808 voltage regulator onto it so it can lay flat.

3: solder the capacitors (optional but recommended) following the scheme. These capacitors are polarised. the short leg needs to be connected to the GND, the longer leg to the +12V and +8V for the next one. Don’t get this the wrong way or they will explode and/or catch fire!

4: Finally solder 2 short wires onto the PCB to connect the output (+8V) and Ground (GND) to the battery separator and solder the long wires to the IN line of the LM7808 and the ground wire to the GND pin. In an adapter, the +12V usually comes from the middle pin. the outer ring is usually the ground. Be sure to check this. Below you can see my print layout. The separator will be in the middle, so place the components on the outsides.

5: Check if it’s working properly. Check the input and output voltages. Make sure you have no short-circuits.

6: Fit everything inside the small battery case

7: Cut a small hole in the battery box’s side top for the cable to come out. Look where the cable gutter in your DSLR is and make it fit.

8: Glue to box close.

9: All done!

Step 4: The adapter

As I said the adapter should have an output current of 1000mA or more. A 12V adapter is recommended, but it can be anything from 11V up to 20V (although 12V is the best choice here). You probably have one of those babies laying around the house. Using a higher voltage adapter will make the LM7808 become warm or hot when under full load. I’ve tested full load (continuous shooting in Medium JPG for 1 minute) and the battery case had come skin-warm but far from hot!

The result

As you see the cable fits perfectly in the camera and the battery grip. Both options work perfectly. The lid closes on both without any problems.

All in all this is a fairly straight-forward build which costs you about 2EUR if you don’t have to buy a 12V Adapter.

Let me know what you think or have any questions