Using PWM LED Dimming for Data Transfer

A project log for The Beamboarder

Create a magnetic 4 watt high power LED head lamp for applications like longboards out of an old hard disk drive for less than 25 $.

LyonLyon 08/19/2014 at 08:100 Comments

For hitting the new requirements of the Hackaday price here a new feature for the Beamboarder and for all the other headlights out in this world. 

Running the high Power LED with DC will only be possible when you hit the forward voltage of 9V of the LED Array.  A  11.1 V Li-Po Battery like this one would be perfect from the capacity but the light output and heat would be much to high:

Thats why I want to use a PWM dimm circuit. In this combination the runtime would also be increased to mulitple hours and the output can be controlled by a small microcontroller. The PWM curcuit can also be used for Data Transfer. A fixed frequency modulated with PWM on the light output can be measured by other road user with a little fotodiode. This would be a very simple way for communication between multiple road users with just one message:

I'am also on this road! Please dont hit me!

This technique could also be used for bicycles and other vehicles that are difficult to see at night on the road. The high amount of light created by the Beamboarder should be able to measure from different angles of the Photodiode.

The measurment of the LED Temperature and the creation of the PWM signal can be done by a very small µC like this one:

Here a paper I found that discibes the light communicaton more in detail: