Making a smart color-changing light bulb is not that hard, but making one that is cheap to mass produce is hard. At $10 per bulb (delivered!), the new GE C-Sleep bulbs are amazingly cheap, especially considering they include a Bluetooth radio.
For Part #1, let’s look at the physical design and construction of these fancy bulbs!
Cutting the top of the bulb diffuser off, we can see the LED carrier board.
The LEDs are mounted on an aluminum substrate to conduct away the massive heat they generate. The sockets in the middle mate to right angle to pins on the vertically mounted board behind. This makes for easy assembly and is a pretty common way of putting together LED bulbs.
There are three different colors of LEDs and the mix of these colors changes throughout the day to generate the desired spectrum. Without the diffuser these LEDs are blindingly bright point sources and I had to use welding goggles to look at them even at the lowest brightness setting.
Unscrewing and removing the LED board shows some white thermal paste that helps the heat flow from the back of LED board to the body of the bulb. Here we also get our first glimpse of the main electronics and they are completely encapsulated in some kind of silicone (which GE probably gets great internal pricing on :) ).
Next we remove the bottom screw cap which is tightly crimped on. The two mains wires feed though a hole in the bottom that is also sealed with silicone. I wonder why they are doing so much work to seal up the electronics? Is it to keep water out.. or electricity in? If you know why, please do tell in the comments!
Once the bottom wires are freed, the electronics module slides out neatly, leaving the bulb body. A little sandpaper reveals that it is a sold piece of cast aluminum. This massive heat sink helps to keep the LEDs from overheating, and gives the bulb a very hefty and solid feel. The white coating seems a little harder to remove than regular paint. Maybe it is a baked on enamel?
The now free electronics assembly has white plastic cladding wrapped around it. Seems like the main board could have slid directly into slots in the body housing and been potted in place there, saving the extra plastic material and a step. Maybe they wanted a belt-and-suspenders insulation barrier between the internals and the electrically conductive bulb body? Comments please!
The plastic cladding comes off easily leaving nothing but a giant chunk of potting between us and the guts!
Here is a nice view of top side showing the pins that mate to the LED carrier board. That white surrender-flag sticking up is the Bluetooth antenna. It pokes though a hole in the LED board so it can have a clear radio view of the world rather than being trapped in what is effectively a Faraday cage formed by the bulb’s aluminum body and LED board. Really nice design. I wonder if having everything all the electronics sealed inside aluminum helps with EM emissions compliance?
It is not too hard to coax the silicone off in big pieces with an X-acto and tweezers. Here we see the electronics module consists of two boards mounted at right angles to each other.
The main board is a pretty typical power supply and is manufactured with low tolerance traces and big 0603+ and SIOC parts. Here I plugged the LED board back in to the top pins to show the assembled geometry.
That neat row of pins protruding along the center come from the digital draughtboard mounted on the back. side. The pins are though-hole soldered in place. I wonder what process they used to make those joints? Maybe a selective solder nozzle? ..but C4 is right next to it. If they used a wave solder on that side of the board, I think they would have needed to stick all those components down with adhesive, no? Post in the comments if you have any ideas how/why they did it this way!
The digital daughterboard holds the ears and brains of the bulb and is made to slightly higher tolerances, but it is still relatively big stuff to keep the process cheap. The board only has components on one side so was almost certainly reflowed. So what kind Bluetooth radio and SoC did GE go for on this super low price/high volume unit? You will have to wait for the upcoming digital teardown to find out!
Tune in next time for the analog teardown where we check out the main power supply board components and design…
FAQ
Q: Why?
A: I happened to have recently worked on a very similar bulb except without Bluetooth, which I think makes for a simpler product. While this new GE bulb is an amazing feat of value engineering, fancier is not always better. I don’t necessarily want a radio and a computer inside each and every one of my light bulbs -especially when each light bulb requires me to install software (assuming I even have an iPhone!) so I can pair and configure it. Maybe a light bulb is an object of beautiful simplicity that should not need to be paired and configured – and should not need a remote firmware upgrade procedure to fix bugs. Maybe you should just be able to screw a light bulb in and flip the switch…(OK, maybe flip the switch 3 times!)
Q: How did you get for them for $10 each?
A: You have to order a 4-bulb starter kit and use the discount code “Sleeptight”.
Q: Will replacing all the bulbs in my house with fancy circadian solar cycle synced smart bulbs make me sleep like a baby and save me thousands of dollars a year on sleeping pills?
A: Umm… Ask NASA?
Q: I just bought one and I can’t figure out how the hell to use it!
A: Yea, they kinda dropped the ball on the out-of-the-box experience. There should be a Quick Start flyer in the box but instead the only documentation (and I mean really only on earth, including the WWW!) is the (easy to miss) 3-step instructions printed on the side of the box…
Note that the App only works on iOS and there is no ETA for an Android App (or even indication that one will ever come).
Once the app is installed, it is pretty straightforward to add a bulb by pressing “bulbs” then “add”. The App will search for any powered bulbs in range and pair with them.
One bulb I tested seemed to crash after pairing, but unscrewing and rescrewing it seemed to fix it. A light bulb that crashes. I did notice that the App has a remote firmware upgrade, so maybe they can fix bugs like this.
Note that once a bulb is paired, it will not pair again unless explicitly unpaired first. This makes sense from a security perspective since otherwise anyone in range could control the bulbs inside your house (and I can imagine bad ways that could play out). Unfortunately, this has the interesting downside that loosing your phone would seem to brick all your paired bulbs. If there is a way to physically reset a bulb, I don’t see it and I can not find any documentation for this bulb at all. Maybe there is a magic sequence of physically turning on and off that will make a bulb pair-able again? Please leave comments if you’ve figured it out!