DIY Distro

7 May

DSLR batteries are simply not suited for live video. It’s enough of a power suck just to do Live View–having to run the extra processing for recording drains them even quicker. As I started to get into shooting motion pictures more often, and began adding equipment to my setup, I realised that power was going to be the major stumbling block.

My initial solution was a generic power distro from China, found via an eBay search (picture above from when I sold it, for which I replaced the V-mount plate with an AB.) Didn’t go for the cheapest, but didn’t want to drop more than $200 on what looked to be the same thing, just with a “Lanparte” sticker on it. Came with two coiled connectors, as well as a dummy LP-E6 battery for my 5D2. Both coiled cables died shortly after I started using it, so I ended up buying some speaker wire and connectors from RadioShack in order to make my own. While the speaker wire was a bad idea (not very flexible) it worked well enough. The outputs were all center-pin positive, and that’s what mattered.

As my gear acquisition began taking leaps forward, I started finding all the annoying little bits about the power supply. There were two different sizes of power connector (5v/7.2v was 2.1mm, 12v/15v was 2.5mm,) the battery plate was facing the wrong direction (I had to pull it towards the camera to remove it, which limited how close I could put it to the body,) and in general, I didn’t really need the exact voltages as much as I needed outputs (and I needed them to be the SAME SIZE. Ugh.) It also had an HDMI splitter built in, but I never used it, because (a) it was on the inside of the rig, (b) I didn’t want to bend my HDMI cables out of whack, and (c) my DP4 has a loop-through, so if I was using HDMI outs I would hit that first.

So I threw something together in SketchUp, based around straight-up wired-to-downconverters stuff. The Chinese power supply was built around a circuit board that handled all the voltage regulation, which is fine for what they were doing (especially with the HDMI splitter.) But I don’t have the time or expertise for those, so I went to the same DC-DC buck converters I used for my Steadicam build. I wanted to have three voltages: 12v for bigger cameras and accessories; 5v for any HDMI or USB stuff I wanted to add (like my Nyrius wireless transmitter and/or an SDI to HDMI converter); and a voltage that could be adjusted at some point. This is future-proofing–I hope I won’t always have a 5D, and if I get another Canon (aiming for a C100) then I can turn that output up to 8.4v to power it. The outputs come in four flavors: 2.1mm coax, 4-pin LEMO, 2-pin LEMO, and a 4-pin XLR. This is for the outside possibility that I use this on a RED Scarlet or Epic that has an XLR-to-LEMO power cable.

This post is just how I did it. If you’re interested in building one, or having me build one, please get in contact with me, but I would love to see you do it on your own. Basically, I’m giving you an idea to start from.

Materials:

  • Aluminum enclosure – this I chose because it was deep/tall enough for a 4-pin XLR. I probably could’ve found a better one that was smaller, but there are a ton of these on Amazon, and I haven’t done the amazingly in-depth research that would require. If you’re not using an XLR connector, you could get a smaller box.
  • LED Display – Not necessary, but nice. I’ll explain why below.
  • DPDT Switch – if you’ve got the LED display, might as well roll with this too.
  • DC Step-down Converters – the 5-pack is a great price. I’ve used these for a dozen small things, and they’re very solid.
  • 15mm Railblock – I like the “lightweight rail block” from SmallRig.
  • Screw terminals (these were bigger than what I had in mind. I would suggest finding a smaller one–see below.)
  • V-mount battery plate – because I have V-mounts. If you have Anton-Bauer/gold mount batteries, use these.
  • 2.1mm jacks – at the very least, these are small and let you put more of them in. You could add any other plugs, but I’m not sure where you’d buy ’em.

The idea of fuses was introduced somewhat after I started working, and maybe I can do that in the future. I’m out of space on the Version 1, but maybe a V2 will add that.

The DPDT (double-pole double-throw) switch & LED display serve a dual-purpose. I have one side set to see the incoming voltage from the battery–this gives me some warning about when I should change the battery–and the other side is the output from the variable voltage converter. This lets me see what it is before I plug a camera in, but also lets me have a display so if I need to adjust in the field, I don’t have to pull out a multimeter.

I marked out the hole centers, and drilled each first with a 1/4″ bit. After that, I used a step bit to cut each hole to the required width–each style of connector needed a different size hole. Ideally, I would’ve had precise punches, because the nature of the step bits can be very rough as far as precision.

The holes for the switch and display were a pain. I basically marked them out, cut a hole in the center big enough for my jigsaw blade, and cut them out. My marks must have been way off, because I spent the better part of two hours one day with a rough file, widening the holes and flattening the bumps so that those components would fit. And now that they’re in? They ain’t ever comin’ out.

Pro-tip: solder your connectors BEFORE you install them. Even if you waste a bit of cable, it’ll be worth it in the long run.

‘Nother pro-tip: look ahead to where you’re drilling. The second-to-top hole cut through one of the screw holes in the box, so the nut is kind-of at a weird angle. It’s managing to hold the jack in, but it’s a dumb mistake to make.

You can see the large amount of space that screw terminal takes up. It’s distributing my incoming voltage and 12v to the connectors as well as the switch, while the variable voltage is wired straight to its ouputs and the switch. I haven’t done enough research to know if it’s okay to run a common ground between all of these (which would save a lot of wiring) but I went ahead and kept it all seperate.

The buck converters are being held in by 3M Command strips, as is the terminal. I’ve used that solution for other projects, and so far haven’t had any failures.

So hopefully this will be a starting point for you. I’ve got some spare parts lying around and might actually build a second, smaller distro, with more/better pictures.

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