Project:SpeedAdjustableBikeLight

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.

Plan

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

Project overview and status is here.

Overview

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.

Todo

• 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?

Electronics

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:).