I was so tired of getting out of bed to turn on/off the ceiling light in my bedroom. So one day when I saw Costco was selling a remote controlled led ceiling light, I immediately grabbed one:
There was nothing special for the installation: You unscrew the old ceiling light, put the new one on, hook up the mains wire using the provided wire nuts. Of course I turned off the switch and double checked the power was off so I don’t get electrocuted.
However, before I hooked up, I think I should take a look at what’s inside: The text printed on the box and the remote controller indicate it has some fancy functionalities:
- Adjustable brightness
- Adjustable color temperature
- Ambient light sensor
- Motion sensor with adjustable sensitivity
- Automatically turning off after a couple minutes
That’s quite a lot of things and I’d like to see how it’s implemented. Tearing this thing apart is probably the easiest thing I ever had. So here are the pictures of its internal:
Of course there are LEDs. They are mounted on a PCB. There is nothing fancy with that so I didn’t take a picture of it. Behind the PCB there are only two parts: A power adapter, and a controller unit. The controller unit has two sets of wires: One set goes into the controller unit, and the other set connects to the LED plate.
It’s quite simple but one thing really surprised me: The controller unit has an FCCID on it! For anyone being interested into RF and electronics, you probably know that FCCID means it’s emitting some sorts of radio frequency, which is not mentioned on the user manual at all. Hmm, of course I did a quick search on google with FCCID WUI-LM561232 and here is it:
So unlike what I thought using a PIR sensor for motion detection, it’s using microwave! I’ve seen a youtube video from Andreas Spiess talking about radar sensors , I think this one is similar. What’s also very interesting is this one operates at “5.75-5.856 GHz” range, which may have some overlap with 5G wifi bands — no wonder in the review section someone says this light was interfering with his wifi — although i didn’t have this issue with it.
To satisfy my curiosity, I pried open the controller unit and here is how it looks:
On the top is an antenna for the sensor module. It’s connected to the main controller board using some header connectors. So I have to bend the headers to reveal what’s under it.
As you can see in the sensor is entirely enclosed in a metal can, which is a common practice for shielding. The sensor connects to the main board with 3 pins, VCC, GND, and Signal — I have no idea how it adjusts the sensitivity of the motion sensor with these pins.
On the main board, there are a couple components. The larger IC is the micro-controller Nuvoton n76e003at20, which is responsible for the main controlling logic. The smaller 8-pin IC has a marking “2904 MZ2812” but I couldn’t find any information about that. Other than those, there are three LED like things, the dark one is the IR receiver, the green one is an LED indicator, the white one I think it’s a ambient light sensor.
It’s not easy to see on the picture, but with a closer look, I can tell the white header has 4 pins, which are GND, 5V, PWM1, PWM2. It’s basically the controller receives 5V power, and then it outputs two PWM signals, controlling the strength of two sets of LEDs with 5K and 3K color temperature.
OK, that’s all about the tear-down. The moment I saw the insides of this ceiling lights, I went to Costco again and bought a couple more. Why? Because this looks like a perfect candidate for a hobby project: it should be very easy to convert this into a internet connected ceiling light without messing up with mains voltage. If i’m going to do that, I want all my bedrooms using this model.