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LED lights and lenses for my bike

I plan to have several strings of LEDs with different beam angles and aiming points - and the appropriate string of LEDs turned on for the current bike speed.


Project journal is now in dropbox/bikelight/project-bikelight.nb

Project overview and status is here.


My motivation is to have fun while learning about designing PCBs, and using microcontrollers, MOSFETs and LEDs - with a simple objective to measure my progress against.

I came across this page that explains the benefits of matching LEDs to bike generators.

Since LEDs seem cheap and the available energy is small, I refined the plan. Build several strings of LEDs with different beam angles and aiming points - and the choose the string of LEDs to turn on for the current bike speed and conditions.

Initial target:

  • generate some diffuse light at low speed
  • generate more focused light at high speed
  • make it work
  • dont break the bank

Advanced target:

  • during the day, flash the LEDs to attract attention.

Next Steps

Pausing for a bit.. reminders for when I get back:)

  • Laser cut solder stencil
    • Test plastic film for chlorine; need propane
    • scale drawing dxf_scale.ulp in dropbox
    • cut stencil (should be easy)
  • Heat source for soldering
    • Marg's box has an electric kettle base and motor controller from vacuum cleaner - that should allow smooth manual heating control in combination with a non-contact thermometer..
  • Test solder some resistors, which I have spare of; test solder joints and try again until I get it right on these!!
  • Build a board ...
    • test as many board solder joints as feasible
    • program MCU on board with test code
    • test board functionality with test code
  • Using head-light code..
    • exercise functionality; observe result; consider
    • improve; rinse repeat
  • Heat sink for LEDs
    • have a test heat-pipe over box
      • need to test its conductivity
      • should test vacuum in pipe?
      • maybe infer vacuum quality from conductivity?
    • have some larger pipe in tools at home - need cap and taps to match
    • need pipe-to-led adapters.. make?

In progress lessons

  • how to use Eagle CAD:
    • to make components
    • to enter schematic
    • to layout a board

Physical progress

Have components, circuit boards, solder paste.


  • Software
  • Solder stencil
  • Surface mount soldering
  • Through hole soldering
  • Testing

Open questions

  • How to mount and cool the LEDs?
    • on a horizontal copper heat pipe
  • How to mount the circuit board?


Plan is now for

  • four LED strings (*)
  1. - very low speed - just a 120 deg med power LED
  2. - low speed - one 30deg
  3. - med speed - one 30deg, one 15deg
  4. - high speed - one 15deg, two 5deg
  • LED voltage sense for fine control
  • light sensor - to allow different night and day policies
  • JTAG debugging
  • possible communications via SPI, TWI, ...

(*) the length of the strings depend on the Voltage generated, and will be changed to match.

This easily fits in the attiny84 - with space for JTAG also.

New link on impedance matching and MCU control of bike lights :). I am not sure what this means for my circuit. My plan is to continue on:).