A few weeks ago, I asked Shane, my dear friend and film-maker, to help me publicly launch the project by making a short video.

As it turns out, Dr. Chris Carpenter is in town this week, and Shane is out of town for the holiday. So Shane corralled his partner in film-making, Arne, into conducting an interview with Chris this morning. It was a lot of fun, and great to meet Arne for real (we’d only met at events and parties before) and really great to get to spend an hour with Chris.

 

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Chris told me that he knows Bizi from the HEAL Africa hospital in Goma, DR Congo (whose nick-name I’ve been mis-spelling until now- it’s not “Buzi”, it’s “Bizi”). He told me about Bizi and now I know that I have a really good, solid connection in DR Congo.

One thing that we spoke about briefly was the possibility of assembling bili lights in DR Congo. Chris felt that it would be a huge benefit to the local economy to have them made there, and that even a tiny wage, by Developed World standards, would be very much appreciated by the locals. I have thought along these lines before, but I had no idea whether it was a good idea… and honestly, I still don’t! There are many ways it could go wrong. But knowing that there is someone there I can trust, namely Bizi, makes me think it may be possible.

I’ve now officially started work on the next generation prototype of the bili light.

As you know from my previous post titled “Project Appeal“, it’s somewhat problematic to find the balance between keeping the bili light project fun to build, and making it more effective and durable. At this point, there is the original version, with 120 5 mm LED’s, and now the new version, with a still undetermined number of Cree XP-E High Power LED’s. These LED’s function at up to 3.5 watts each, and they’re obviously incredibly bright. There are two added bonuses: one, they will have a much longer half-life than the 5 mm LED’s, and two, they are much closer to what we believe may be the most efficacious wavelength for bilirubin phototherapy.

But now I have a new angle: these high-power LED’s are fun to work with, and at the same time, they suck so much juice that it’s really sub-optimal to use resistors for current limiting – the two 50 watt resistors shown below are hot enough to cook on, and the LED’s are not even running at full power. So I’m going to start learning about pulse-width modulation and switching power supplies, with some help from Bob.

Here’s a picture of the test bed as it looked yesterday; it’s already changed quite a bit:

In the center is the “5-up” board that I’ve been concentrating my efforts on – “5-up” just means that the MCPCB has five surface-mount XP-E LED’s on it. I took the lenses out of an old pair of Ray-Bans to tone down the light for the photo- otherwise it’s too bright for the camera. Just to the left is an MR16 LED bulb I bought at Fry’s. I opened it up and replaced the MCPCB inside with one of the Cree 1-ups (i.e. a single LED). I actually tried the 5-up there first, but two problems with that: one is that the electronics and the optics in the bulb are made for a single LED, so they would probably not light up the 5-up. The other problem is that the 5-up is wired with the LED’s in series, and their minimum forward bias is 3V. That means that you need a minimum of a 15V power supply to make them turn on. Here, the 5-up is powered by a 24V power supply (or actually two 12V power supplies in series).

To the left of the MR16 is the package of tester MCPCB’s that I received from Vachik at Cree, and above that you can see the box they came in. Big shout out to Cree and most especially to Vachik! Thank you!

The white board that the 5-up is attached to is a hex-cell-core aluminum panel made by Pacific Panels, the company Michael works for. The idea was to try it out as a heat sink for the MCPCB’s/ LED’s, and it has performed wonderfully.

There is a terminal strip that I’m using for making all the connections screwed onto the top of the board, and attached there, you can see two 50-watt resistors that are limiting the current for the 5-up. In this photo, the LED’s are running at about 2.4 Watts each.

Here is a link to the PDF of the Specification Sheet for the Bili Light and Bili Light Meter.

…and here are the specifications that are on that PDF:

Bili Light and Bili Light Meter Prototype Specifications:

Bili Light:

• Input Voltage: 12 Volts Nominal (12 to 14 Volts)
• Power Consumption: 12V at 2.4A = 28.8 W
• (120 Cree C503B LED’s at 20 mA each)
• Nominal Center Wavelength: 470 nm
• Nominal Distance for 30 to 35uW/cm²/nm exposure: 48 cm (19 inches)
• Power Source: 12V adapter, Input voltage 100 to 240V AC, 2.5A minimum
• Alternate Power Source: Car Battery adapter (12V batteries only!)
• Connector: Coaxial Power Connector 5.5 mm x 2.5 mm

Bili Light Meter:

• Input Voltage: 9V battery – or – 7 to 35V External Power Supply
• (Can be used directly with the same model power adapter as the bili light, or powered by the “aux power” connector on bili light’s 12V power cable)
• Power Consumption: About 20 mW
• External Power Connector: Coaxial Power Connector 5.5 mm x 2.5 mm

CREDITS:

• Robert Blick (bobblick.com): electronic design consultant.
• Chris Carpenter, MD: Concept and Inspiration
• Shumit Dasgupta: Education and curriculum
• Michael Rothberg (Michael Rothberg Design): Industrial design consultant, Aluminum panel box fabrication.
• Gever Tulley (Tinkering School): D.I.Y. Concept consultant, moral support.

I was speaking with Chris Carpenter today and came up with the phrase/concept “project appeal” (I’m sure I’m not the first, it’s obvious)…

The 5mm LED version of the bili light has a lot of “project appeal” because the parts are so easily available and cheap, and because the soldering has that good “knitting project” nature to it- repetition in a good way, seeing something come together as you work. Is there a catch phrase for the concept of “good and creative repetition”, as opposed to the mind-numbing repetition of working on an assembly line? The word “repetition” has oodles of negative weight at this point, and I think it’s because of the assembly line, and the types of menial labor that come out of that. I have good role models in my family for GOOD repetition: knitting, crochet, spinning, weaving, all of these are very creative activities… in fact, it occurs to me that human creativity probably started, millennia ago, with these very activities.

Colin brought this up when we were hanging out at his bbq a couple weekends ago – the concept that the doing of the project has value, regardless of how technically correct it is or rather, perhaps in spite of the fact or even because of  the fact that the project is not something that an industrial production company would do. That’s part of the spirit of DIY: Do It Yourself because some mega-corporation is not going to do it for you, and if they did you wouldn’t want what they made anyway.

Anyway, the soldering of 120 or so 5mm LED’s has a lot of “project appeal”, and the question is: how to weight Project Appeal against a different project that might have less project appeal but better therapeutic efficacy?

I’d like to get the project to a place where you can have the best of both worlds, and with the MCPCB’s Vachik sent me, I can see how that might come together.