Technology Marches Forward


It’s been pretty obvious from the start that the 5mm “bulb” LED is not actually the ideal part to use, in this day and age, for making bili lights. But as I said in a previous post titled Project Appeal, way back in July 2011 when Luma League had not even shipped the first 5mm LED-based light yet, the 5mm approach has a set of benefits that go along with the 5mm LED’s; namely: the 5mm LED’s cost less than $0.20 each and they’re fun to solder. The circuit boards are cheap too, we buy the copper-clad project boards for about $2 each. And soldering 120 LED’s and 60 resistors is a lot of opportunity for a lot of kids to do a lot of soldering and have a lot of fun.

On the other side of the equation is the modern SMD – Surface Mount Device – High-Power LED. While the 5mm LED’s consume 20 mA (milli-Amps) and turn that into blue light, modern high-power LED’s turn at least 350 mA into light, and with the new XT-E LED’s from Cree, some can do more than 500 mA. And they’re more efficient than the 5mm type, so they produce a LOT of light.

Today, I’ve been in touch with Cree, and I’m hoping to get some samples of their new Royal Blue XT-E led’s from them. In quanitity, they cost about $1.50 each, but so far, the smallest minimum order I’ve seen is 450 units… out of my price range for now. They also sell star boards that hold one XP-E or XT-E LED for about $1.10 each. So I might be able to solder together a high-power LED star board for as little as $1.60, as opposed to the retail price of about $4. That’s a big difference.

Today I also ordered a couple of pieces of MakersLED extruded aluminum LED housing from LEDSupply. I’ve not been happy with LEDSupply’s customer service in the past, and their prices are high, but this stuff is very cool, and I want some, so I ordered it. It has T-shaped slots to receive fasteners, and the slots are spaced to make it easy to position star boards on the bottom face. There are six T-slots giving you five tracks along which to attach star boards. The design is cunning in other ways too, and they’ve come up with a very intriguing range of accessories to finish, hang, and cool the aluminum and the LED’s attached to it.

Between the XLamps and the MakersLED extruded aluminum, we can come up with a very cool new design for bili lights that will have as much project appeal as the 5mm LED based design. It will not be a platform for a lot of practice soldering, but it will be fun and easy to put together.



Bruce from Tennessee saw the post on the Make Magazine blog in March and contacted me to ask if there was any way he could help. I soon found him to be a great ally. He’s interested in helping to make circuit boards for the bili lights, and after a flurry of emails back and forth, today I received the first prototype PCB (or actually “Milled Circuit Board”, as it was actually done on a CNC router) in the mail. We’re well on our way to having circuit boards that will make bili lights even simpler to produce!

Thanks Bruce!

The Vanderbilt-Guatemala Connection

Becca Hudson, a student in the Biomedical program at Vanderbilt University, contacted me a couple of months ago about making a bili light to take to Guatemala. In true Tinkering spirit, she modified the design to suit her needs, and made a beautiful bili light that is now in use in Guatemala. Here are a few pictures from Becca. One shows Becca with Sergio, the chief engineer

Cynthia Paschal, Becca’s teacher in Biomedical Engineering, said:

“The light was indeed a success and was delivered to Hospital Nacional de Pedro de Bethancourt [English translation] in Antigua, Guatemala

I look forward to getting more updates from Vanderbilt and Guatemala.


Soldering at Chabot

Luma League was at Chabot Space and Science Center on Saturday, April 14th. Here are a few photos from the day. Fourteen people, 11 of them under 11 years old, contributed their time and talents to solder an LED board that will be going into a Luma League Phototherapy Light for one of our partner hospitals in the developing world.

Want to get involved? You can Volunteer to teach soldering at Luma League’s booth at Maker Faire, coming up in three weeks! No prior experience needed, we’ll be holding training sessions for volunteers.

Molly’s Research Project

Molly Soldering a bili light

Moly Soldering

Molly and her dad, Art, who is an old friend of mine, came by on Sunday to talk tinkering, bili lights, and Make-ing. I asked Molly if she wanted to be the first guinea pig for the activity I’m planning for Maker Faire.

Molly’s an old hand at soldering so she didn’t need much in the way of direction. She soldered the three blue LED’s and the resistor that limits the current for them, and a few minutes later she was attaching the power supply.

Molly looks at the blue light from LED's she soldered for a bili light.

Good soldering, Molly!

She got the “long version” of the lecture- basically, everything that’s written in my FAQ and then some- on jaundice and bili lights. She immediately came up with her own research project: since the yellow color of bruises is caused by bilirubin, would a bili light help bruises to heal? Molly is an active soccer player and her left knee is quite bruised at  the moment. I said I don’t know, but I think it’s worth finding out, so I gave Molly the a kit to make one-half of a bili light: one project board, 60 LED’s, 20 resistors, a power supply, and a power connector. Molly’s going to try phototherapy on her bruises and report back the results. And Molly and Art will be helping to host the LumaLeague booth at Maker Faire, so you’ll be able to see her handiwork there!

Made In DR Congo…?

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.


View HEAL Africa Hospital in a larger map

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.

The XP-E Experience

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.

Specification Sheet

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


  • Robert Blick ( 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.

Parts & Pricing

Now that the first two bili lights and meters are out the door, I’ve been compiling parts lists and pricing for the project (including both the light and the meter).

Note that the parts list here is for the 5mm LED version of the light, which may be deprecated – and soon! – based on what we’ve learned recently and where we decide to go from here, but I think it’s useful to publish what I’ve done so far. It’s provable that the 5mm LED’s will work for transcutaneous phototherapy, but see my previous post regarding “project appeal”: that’s the trade-off.

In summary, the bili light itself (including a completely made-up number for the aluminum panel pieces that make up the box) costs about $89, and the bili light meter costs about $45. These prices include California sales tax, even on the items that I mail-ordered from out of state. Note that these are estimates based on the shipping costs I paid divided by the quantity I bought. And I’ve sent several power supplies with each light, as backups, but since only one is needed per light, there’s only one in the parts list.

The actual plans will follow in due time, but if you want to get started, the construction of the light is very simple: three LED’s in series with a 120 ohm current limiting resistor; repeat 40 times.

Project Appeal

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.