Cheap and Easy PSU for Canon EOS





Introduction: Cheap and Easy PSU for Canon EOS

About: I'm an Italian freelance structural engineer, graphic designer and photographer, and I'm teaching physics in Waldorf schools. I always investigate electronics, robotics and science in general, I'm a passiona...

I think lot of guys here on Instructables know how much satisfaction is obtained building a gadget entirely by ourselves, but... sometimes it could be a clever solution opting for some nice and ready accessory. I think this is one of these cases.
I recently had the need to have a power supply for my Canon DSLR, an EOS 40D, to make some timelapse. For this pourpose I've bought an LM2596S step-down adjustable power supply module from eBay, it's very cheap, efficient, compact, and (I hope) safe... and it fits exactly inside my exhausted lithium battery case. And this instructable could be handy adapted for almost any digital camera battery, the only requirement is that the case contains the power supply module.

Step 1: Intro

The new psu is intended to work with a wall-plug transformer the same as with any DC power source between 9 and 35V, as a car battery or almost any wall-plug psu. This could be very handy in case of timelapses, gigapan shots, or long movies.

Step 2: What's Inside?

I've made the same modifications on two batteries, because both of them were exhausted. They weren't Canon batteries, indeed the original ones are almost ethernal.
You have to cut/crack the plastic casing all around the perimeter, because it's glued verty sturdy. Inside you'll find two 18490 Li-ion batteries, which are very rare to find to replace.

Step 3: Keep the Shells

Separate the battery parts unsoldering the battery contacts, and clead the case edges with a cutter, they should fit each other so we'll glue them at the end.
Maybe you wish to keep the protection circuit as replacement...

Step 4: Drill the Hole

Now take misures of the aperture which you find on your Canon. It's a little rubber door which you can bend to let the wire pass through. I've found that in battery-grip the aperture is in a different position, but if you're powering the camera by an external powersource probably you don't need the battery-grip. So I've opted for the in-camera wire position.
Drill an hole in that position and file it or cut it untill it becomes of the same shape of the wire. I've also added some heat-shrinking tubes to toughen up the cable extremity.

Step 5: Glue the Circuit

Check that the circuit fits in the battery case, I've had to file a corner to make place for the cable.
I've insulated the two unused contacts, and also added a piece of tape to not let the pcb touch them.
Then I've used a double-tape to lock the circuit in place. I've added another layer of tape over the one you see in the pictures.
You can then begin to solder the wires on input and output terminals.

Step 6: Solder It

You can see the glued pcb in place. You can now connect a power source to the cable ends, maybe 12 or 24 volts work good. With a multimeter misure the output voltage and turn the potentiometer until you'll obtain an (almost) exact voltage of 7.4V. 

Step 7: Label It

Now you can add the DC input range on a label behind the battery, together with output voltage and plug's polarity scheme. I've printed some coloured labels so you can cut them and glue into the shape of the previous one.

Step 8: The Socket

As female socket you could buy one of those nice ones which already have a cable connected. I've used a different type, and I had to solder the wires on them. Then I've enclosed them into some heat-shrinking tubes to obtain a better look.
[UPDATE] You can now see the detail of the cable coming out from the rubber cover near the battery door.

Step 9: Done!

Check another time that everything works good, let the power connected for a few time, try different input voltage, bend the cable, flex it, pull it, also chew it if you dare... it's better to get a shock now than to find your three months timelapse failed because of a bad soldering! Obviously I'm fooling with you, always pay attention to high current sources as car batteries, they're very dangerous!
Everything is ready, it's time to glue the shells pair, maybe with two elements glue, and try your new power adapter!



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    39 Discussions

    Hi there,thanks .i've done it but please help me I had problem err99 please shooting is not possible. Please turn off the camera or remove the battery" ? ?

    1 reply

    i know this instructables is kinda old but im curious if i can use dc-dc step up instead of a step down module. i want to connect it to a powerbank with 5v output.

    the modules looks like this:

    2 replies

    yes you probably can, if it supplies enough current :-)

    how much current does it need? btw thanks for the reply

    I recently cracked an AC adapter dummy battery and was surprised how little was inside: just a jack, two capacitors and the contacts connected to a PC board. Would you have any idea how to determine what these type of capacitors these are and their values? They're so tiny and don't seem to have any markings on them. I'm not very electronics-savvy, so if anyone might be able to give me an idea of what their values might be, or if I could substitute something else for them, I would appreciate it. Thanks a lot.

    1 reply

    The reason this adaptor is so tiny, is that all the electronics andrea_biffi put into the battery casing are located in the wall adapter of your battery AC adapter.

    You can measure the capacitance of the capacitors using what is called an LCR-meter. It not only measures capacitance (C), but also inductance (L), resistance (R).

    The capacitors are bypass capacitors, to filter any noise, that got coupled into the cable between the wall adapter and the dummy battery. They also compensate the inductance of that wire in case of sudden changes in the current.

    My guess is, that the smaller capacitor is 100nF and the larger capacitor is in the range of 1 - 10 uF. The exact values probably don't matter much. Common capacitors of this type can deviate from their labelled value by -20% to +80%(!).

    This was a great post. Used it as a building block for creating my own PSU with a few modifications. Ended up casting my own hollow battery shell in resin you can view some of the pictures here.

    Thank you so much for the guide. I was just looking into using this exact converter. However, I am concerned about the heat. According to the spec sheet for the LM2596S, a heatsink should be used when over 10W. The stock batteries are rated for 7.4V at 2A. Unfortunately, I don't have the tools to measure how much power the camera uses. Have you ever checked for heat build-up in the battery enclosure after prolonged use? I

    1 reply

    I doubt the camera has a peak of more than 10w. Batteries are so powerful to last many hours. I never checked the heat, but I used for time lapses so there is a certain interval between pictures and certainly enough time to heat down.

    Video mode on new cameras could be different, but you can always check if the psu is hot after some minutes of video.

    Nice job! Would be nice if Canon included a DC input from the factory, wouldn't it? Especially since we are using them for video a lot now, which burns a ton of battery.
    Can you show the camera with your battery installed? I would like to see how you have the wire routed.

    3 replies

    Yes I'll take the picture soon. Canon always wants to sell more accessories, see also timelapse features or flash transmitter... :-(

    If you don't want to risk burned fingers you can order something that works like this for the Canon T2i on Ebay for around 10 bucks. If you have a larger capacity 7.4 volt power source (e.g. old canon camcorder battery) the dummy battery part of the above adapter can always be cut off and used instead of the AC adapter.

    Thanks for your advice, I've been using my DIY PSU with success for last seven months with not a pinkie burned ;-)
    My power source is 220VAC or 12VDC, this last connected directly to my dummy battery.

    Its a good solution, i have a 550D, same solution for it??
    wich module did you use? i find this one cheap:

    1 reply

    Hi there.
    Great Instructable. I have an EOS40D and reckon your solution it would solve another problem as well. - Do you know if your battery has enough charge left to power a sensor cleaning session? With this solution it doesn't matter - just plug in and go.
    Even with my battery grip -two batteries- I have to recharge just to be sure that the large drain of holding the shutter open won't flatten the batteries. Problem solved. Thank you.

    2 replies

    Great instructable !!
    On the protection diode, have you wired it in parallel with the supply?