Basic Information:
Brand: Merkury
Model: MI-BW904-999W
Chip: WB2L
Vendor: Walmart (bought in December 2020 for about $5)
Teardown Photos
The plastic dome is glued with some compound to the aluminum base. I had to heat it up with a heat gun, and the dome came off pretty easily. Unfortunately the LED board is glued with another compound that was not so easy to remove. I user the Force and a screwdriver, but this all is not necessary (see below).
As you see (Fig.4) the lamp's brain is a WB2L module. The black IC next to it is a BP1638 driver (this will be important later). I decided to try out Tuya Cloud Cutter (CC henceforth). CC doesn't know this exact model, but knows MI-BW932-999W. I downloaded OpenBK7231T_UG_1.15.566.bin firmware from the OpenBeken github. (Note the UG - since we will be programming it OTA is is important to take the right firmware.) I then flashed the lamp following CC's instructions. After the CC is done you should see a wifi network with SSID OpenBK7231T_XXXXX. Follow the setup instructions from OpenBeken: connect to the WiFi, open 192.168.4.1, enter your SSID and password, enter your MQTT server (if needed).
Pin definition
Now comes the fun part. WB2L has 5 pins that can drive the peripherals. It turns out the module is connected to BP1738CJ driver located next to it on the main board. Looking at it application diagram:
We see that the only inputs it takes are three PWM for red, green and blue. The lamp as you see from Fig. 3 above has a circle of color LED and a circle of white LEDs. The IC on the LED boards has a label BP5711J. I couldn't find a datasheet for that, but found one for CN5711
- so it looks like this is the driver for the high power white LEDs.
So all four RGBW LED strips are driven by PWM pins of WB2L. After some permutations I found that
P6 -> PWM0
P8 -> PWM3
P24->PWM2
P26->PWM1
If you follow this arrangement the colorwheel in home assistant will give you the right colors. Make sure to select "Flag 3 - [LED][Debug] Show raw PWM controller on WWW index instead of new LED RGB/CW/etc picker" otherwise the interface will messed up. Then I paired the light bulb with Homeassitant using the native OpenBeken function, and voilà I have a $5 no cloud lamp.
Brand: Merkury
Model: MI-BW904-999W
Chip: WB2L
Vendor: Walmart (bought in December 2020 for about $5)
Regular disclaimer: electricity kills (some), always remove power, tear down at your own risk, etc.Teardown Photos
The plastic dome is glued with some compound to the aluminum base. I had to heat it up with a heat gun, and the dome came off pretty easily. Unfortunately the LED board is glued with another compound that was not so easy to remove. I user the Force and a screwdriver, but this all is not necessary (see below).
As you see (Fig.4) the lamp's brain is a WB2L module. The black IC next to it is a BP1638 driver (this will be important later). I decided to try out Tuya Cloud Cutter (CC henceforth). CC doesn't know this exact model, but knows MI-BW932-999W. I downloaded OpenBK7231T_UG_1.15.566.bin firmware from the OpenBeken github. (Note the UG - since we will be programming it OTA is is important to take the right firmware.) I then flashed the lamp following CC's instructions. After the CC is done you should see a wifi network with SSID OpenBK7231T_XXXXX. Follow the setup instructions from OpenBeken: connect to the WiFi, open 192.168.4.1, enter your SSID and password, enter your MQTT server (if needed).
Pin definition
Now comes the fun part. WB2L has 5 pins that can drive the peripherals. It turns out the module is connected to BP1738CJ driver located next to it on the main board. Looking at it application diagram:
We see that the only inputs it takes are three PWM for red, green and blue. The lamp as you see from Fig. 3 above has a circle of color LED and a circle of white LEDs. The IC on the LED boards has a label BP5711J. I couldn't find a datasheet for that, but found one for CN5711
- so it looks like this is the driver for the high power white LEDs.
So all four RGBW LED strips are driven by PWM pins of WB2L. After some permutations I found that
P6 -> PWM0
P8 -> PWM3
P24->PWM2
P26->PWM1
If you follow this arrangement the colorwheel in home assistant will give you the right colors. Make sure to select "Flag 3 - [LED][Debug] Show raw PWM controller on WWW index instead of new LED RGB/CW/etc picker" otherwise the interface will messed up. Then I paired the light bulb with Homeassitant using the native OpenBeken function, and voilà I have a $5 no cloud lamp.
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