Smart lightbulbs cost your firstborn child. Which is a shame, because smart lights unlock tremendous potential for home automation, energy savings, and all sorts of cool projects.
If only there was a way to control your lights without breaking the bank…
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And now there is! For $19 on Amazon, you can get a 4-lightbulb kit from China that ordinarily is limited to 4 channels from a single remote…but with some creative hacking, can be used to control an unlimited number of channels using an arduino and a very simple RF module!
Here’s a video of them in action as part of our smart bathroom project (Instructable for that coming soon!):
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Time required: 1-2 hours
Total Cost: $19 for four sockets ($5/socket), ~$20 for a transmitter
You should know:
Materials:
- A 4-pack of Vktech Wireless Light Bulb Holders
- Arduino Uno or similar
- 315MHz RF Link Transmitter
Tools:
- IC Clips/hooks
- Bus Pirate (we used the sparkfun version)
- Small Phillips screwdriver
- Computer with a micro USB cable
- A breadboard and spare wire (solid core is best)
Step 1: Reading the EEPROM
We’ll start by cracking open one of these light sockets and reading its memory. Grab your screwdriver and remove the two phillips screws holding the housing together. The case should fall open and reveal the PCB inside.
If you look around, you’ll see a few capacitors, some diodes, a big box (the relay), a long IC (the microcontroller), a separate board tacked on (the RF receiver), and a little 8-DIP chip marked 24C04 – this is the EEPROM that stores the RF command to turn on the bulb.
Let’s take a closer look at what the memory chip holds, shall we? Using the bus pirate and the datasheet for the EEPROM chip, wire up a circuit like the one shown. You should have:
- Bus Pirate VCC -> chip VCC (and to VPU, the pullup pin of the Bus Pirate)
- Bus Pirate GND -> chip GND
- Bus Pirate SDA (MOSI, Orange for Sparkfun BPs) -> chip SDA
- Bus Pirate SCL (CLK, Yellow for Sparkfun BPs) -> chip SCL
- Bus Pirate VPU -> Bus Pirate VCC (the pullup I/O pins are driven from this pin)
For more detail: Cheap Arduino Controlled Light Sockets – Reverse Engineering RF
