© 2010 Marcus Griep

Star Trails over Big Pond in Lewis, NY; 1-hour exposure, July 2010

For most situations, the stock 1080mAh, 7.4V batteries that come with the Canon T1i¹ will work pretty well. In some other instances, including time-lapse and star-trail, that amount of power doesn’t cut it. For these types of photography, either the camera needs to be on but inactive for a long period of time, or needs to have the sensor enabled for a long exposure. When I last used my T1i for a long exposure, the 1800mAh extended battery pack I used lost power after about 3 hours, giving an approximate power need of 600mA while the sensor was exposed.²

To get around this battery life problem, Canon provides an AC/DC power supply and coupler that you can use to power the camera. Unfortunately an AC power supply requires a connection to the power grid, a generator, or a power inverter. In the middle of the Adirondacks where I am most likely to do long-exposure photography, an AC connection is just not feasible and a power inverter is inefficient. There are also professional battery packs that can be purchased specifically for astrophotographers, but the couple I found were prohibitively expensive. The third option was to use a battery grip provided by canon, but at $180 for just the grip, I was convinced there was a cheaper option.

Canon T1i running on XPAL battery pack

This led me to the realization that I already had on hand an Energizer XPAL XP18000 battery pack. I use it when I travel on long trips as an extra battery for my laptop and charger for my cell phone. This pack is light and portable at only about 17 ounces and less than 8 inches long and 1 inch thich and comes with a bunch of connectors for laptops, cellphones, and other gadgets. That 18000 in the name indicates that the battery stores 18,000mAh of power and sports 3 different outputs in varied voltages (5V, 10.5V, and 19V). Since I already had a nicely powerful battery pack, I determined I’d use it to power my camera.

T1i rated at 8.1V

Unfortunately, I needed to regulate the voltage. My Canon T1i is rated to take an input of 8.1V DC. The camera will accept 10.5V DC, but doing so is dangerous, may break sensitive components in the camera, cause fires, physical harm, or worse: void your warranty. I don’t recommend you do it, and if you do over-volt your camera, you do so at your own risk. After searching around, however, I found that some earlier enthusiasts had succeeded in making a DC/DC power supply for their own cameras. Resolving to do the same, I pulled together everything I needed to build the power source.

DC/DC Electrical Diagram

Combining resources I found from Daniel McCauley and Texas Instruments, I determined the circuit I would need to build out the module. At the center of it all, and hardest to get a hold of, was the PTN78020W module which actually does the conversion. This module accepts up to 36V as an input and can output anywhere from 2.5V to 12.5V. Of the other electrical components mentioned in the parts list, most are recommended to ensure the power in and out of the regulator is free of noise. Consult TI’s official documentation to ensure that, if you use fewer components, you include the mandatory capacitors in the correct locations.³

The installed PTN78020WAH module

Because I don’t have the skills to produce a custom board myself, and since fabricating a single circuit board is not cost effective, I used a standard solderless breadboard which fit in my enclosure.⁴ For the input, I used a 2.1mm(ID)/5.5mm(OD) jack which mates perfectly with the base 19V cable included with the XPAL battery pack.⁵ For the output, I picked my own jack/plug combination since I needed to make a cord to go from the power supply to the camera’s DC coupler.⁶

Finished power supply

After assembling all the components as described in the electrical diagram, installing the plugs into the enclosure and soldering things together, the project looked as pictured. Of special note is that the PTN78020W does not fit easily into the breadboard. I had to bend several of the leads to get it to sit properly. I don’t recommend this, as you are likely to end up with a $30 (retail) broken module and nothing to show for it.

Verifying 19V to 8.1V conversion

Once it was all put together, I used a multimeter to verify that I was getting the desired voltage out. I was able to verify that I was hitting my target 8.1V very closely, and once I hooked it up to the camera, I was showing a “full” battery. I used it this past weekend when I attempted a 4-hour long exposure (unfortunately I had the exposure misread, and didn’t get the result I wanted). After the 4-hours taking photos with the LCD viewscreen enabled, I hadn’t even exhausted a quarter of the XPAL battery’s power.

DC/DC Power Supply Circuit Board Design

As an after-exercise, I downloaded a circuit board CAD program from Pad2Pad—they fabricate custom circuit boards and prototypes—and designed my own circuit board. Unfortunately, as I said before, it’s not cost effective for me to purchase a single board, but if I get some interest in this, I’d certainly purchase several and manufacture the power supplies myself and ship one to you. The price I’m looking at, which includes the power supply and 6-foot cord connecting to the DR-E5 is $70. This price is about the same as the mass-produced AC power supply provided by Canon, so the $70 price is a value for the hand-manufacturing. You can buy the DR-E5 coupler for around $30 on Amazon (see link below). If you already have an AC adapter, then you are likely to already own this coupler. If you’re interested in an 8V DC/DC power supply (or 12V for your Canon 1D, or other custom voltage), send me an email: photo+power@xpdm.us.

Disclaimer: I’m not an electrical engineer. I have not vetted this design with an electrical engineer. I am an amateur who loves photography and found a tool to continue to improve my art. Completion of this project is done at your own risk to yourself and camera. If you take issue with the circuit or anything else, feel free to leave a comment.

Parts List

Part IDs in parenthesis lead to Digi-Key parts.

• Resistors
• R₁: 3.9kΩ 5% 1/4W (3.9KQBK-ND)
• R₂: 2.7kΩ 5% 1/4W (2.7KQBK-ND)
• R_set: 5.9kΩ 1% 1/4W (5.9KXBK-ND)
• Inductors
• I_1–3: 3.9µH (M8316-ND)
• Capacitors
• C₁: 1µF 50V Ceramic (445-2889-ND)
• C₂: 2.2µF 50V Ceramic (478-4472-ND)
• C₃: 330µF 50V Electrolytic (P11258-ND)
• C₄: 470µF 16V Electrolytic (338-1751-ND)
• C₅: 1µF 25V Ceramic (445-2857-ND)
• C₆: 100µF 25V Electrolytic (P11258-ND)
• Diodes
• D₁: Schottky 40V 1A (1N5819DICT-ND)
• LED_1–2: Red Panel Mount LED (L10061-ND)
• Voltage Regulator
• PTN78020WAH (296-20515-ND)

Energizer XP18000 Rechargeable Power Pack for Laptops

Xpal Power, Electronics, Too low to display

Canon ACK-E5 AC Adapter Kit for Canon Digital Rebel XS & XSi Digital SLR Camera

Canon, Electronics, $60.28

Canon DR-E5 DC Coupler for Canon Rebel XS and XSi Digital SLR Cameras

Canon, Electronics, $25.00

1. 1800mAh for the 5DmII, 2300mAh 11.1V for the 1DmIV [↩]
2. This is just an estimate. For a D60, Daniel McCauley measured 400mA required while the shutter was open. See his 8V power supply guide, on which this one is based. Variations will also occur with the ambient temperature as well, so your mileage may vary. [↩]
3. The power supply doesn’t work optimally if there is electrical noise on the input side. Also, because the PTN78020 is a switching voltage regulator, it introduces electrical noise at the frequency of its internal switching. [↩]
4. It is important to note that the PTN72080WAH module does not sit well into the standard breadboard. I had to “adjust” a few of the leads so that it could fit into the breadboard’s grid at all. This is why I would much prefer manufacturing the printed circuit board I mention later in this article. [↩]
5. I chose the 19V output because the PTN78020 module requires a voltage difference of at least +2.5V from the target output voltage. Using the 10.5V output puts me right at that limit, and I’d rather have a large buffer to avoid undervolting the module. [↩]
6. The DR-E5 coupler requires a 1.1mm(ID)/3.0mm(OD) right angle plug. The right angle is tight, and it took me a good deal of searching to find a plug with a short enough lead to fit in the confined space. The jack/plug I used on the other end of the cable was a 1.3mm(ID)/3.5mm(OD) which happens to fit into the 9-12V plug on the XPAL battery pack. [↩]

Over the past several months, I have really stepped up my photography to a serious level. In that time, I’ve been dabbling in landscape, portrait, music, journalistic, and model photography. Recently, though, I had the opportunity to be a part of a show put on by Music Ecology. Each month, they put on a Visual Enlightenment party at the Wonder Bar in Allston, MA.

I was one of six artists that were selected to have our artwork hang in the bar during the month of July. On the right above, you can see the layout I chose to go with and clicking on the image will link to a gallery where you can see larger versions of photographs.

I chose to have a couple of themes run through the display. At the top are two fall images from northern New York. In the center is a photograph (featured) of the New England Holocaust Memorial where a person’s face (my friend Justin Kwan) stands as the backdrop to the ID numbers given to prisoners in the concentration camps. On the right are a couple of animal photographs with very narrow depth of field, bringing extreme sharpness to the faces of the sparrow and turtle.

The smaller photographs arrayed around the main centerpiece include a lead crystal car sitting on a reflective black tile. On the top left (featured), Scott Strazzullo plays his guitar during the Songwriters’ Night at All Asia Bar in Cambridge¹. On the top right, a 15-minute exposure (with the help of an ND400 filter) of one of my company’s week’s-end “workshops”. On each side in the middle are book pictures. To the left, the Bible, Square, and Compasses of my mother lodge, Mt. Horeb. To the right, a book of magic tricks turned to a page showing a coin trick.

The bottom three are of special interest to me, and I’ve singled out one to the left here. All three are of the Champlain Bridge, also known as the Crown Point Bridge. Or, rather, they were. As I mentioned in my earlier post, the bridge was demolished on December 28, 2009. The photograph on the left shows the bridge as it was on the somber morning of its demolition. The center (featured) and right photos show the deconstruction and ruins left behind by its demolition. This weekend, I’m going to be back up in New York and plan to extend the series, getting additional photographs of the deconstruction and re-construction process.

All in all, the staff at Wonder Bar were great and very accommodating to my layout whims. I really want to thank them, Music Ecology, and Polina Volchek in particular for organizing it. All of the my prints are on sale as are several of the other artists on display there. If you are interested in purchasing a print, you can do so either through my online gallery or by emailing me directly at photo@xpdm.us.

Hoya 77mm Neutral Density ND-400 X, 9 Stop Multi-Coated Glass Filter

Hoya, Electronics, $134.99

1. You can see other photographs from that night in a gallery dedicated to the June 2010 Songwriters’ Night at All Asia Bar, including photos and video of Jourdan Rystrom and Norman Kim. [↩]