LED lamp is a small project that started with the idea of adding more functionalities for my book lamp. It happened that I bought a led lamp with only one light intensity for each led color ( there was warm and cold white ) and it actually was too strong for reading and therefore I needed a lighter intensity. Then I came up with the idea of replacing the controller of the book lamp with a small microchip microcontroller which was pin to pin compatible.

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The book lamp is a battery powered device with

• one tactile button for interface.
• 2 sets of led: WARM light and WHITE light

Everytime the button was pressed the lamp changed its state between: System Turned OFF, WARM LIGHT, WHITE LIGHT, and both lights ON. there was no intensity control.

As the lights were two strong, the first thing I thought was to implement a light intensity control. For that, I also extended the functionalities of the button to respond to events like :

• Single click ( to change the light composition )
• Holding the button ( to change the brightness )
• and, Double click ( to turn off the device )

with those new events responses it was also implemented a new scheme of possible lights composition:

Then, it was implemented a brightness control of 5 levels pre-defined.

uint8_t const set_brightness[5] = {10,20,30,50,100};

100 represents 100% of brightness, 20 represents 20% and so on;

The percentage of each light is calculated by the formula below ( yellow refers to the warm light )

light_brightness.white = (brightness * light_ratio.white)/ ( light_ratio.white + light_ratio.yellow);

light_brightness.yellow = (brightness * light_ratio.yellow)/ ( light_ratio.white + light_ratio.yellow);

• MCU: PIC12F1840
• Compiler: xc8 (v2.1)