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Bike lights seem to be popular topics at the moment, and we are returning to the theme. Our Technology Editor, Steve Bush, has flagged this project, which is based on powering halogen lighting rather than LEDs.
Essentially, battery voltage levels are measured by a microcontroller that calculates the duty cycle to achieve a desired output power.
The designer describes the problem thus:
Essentially, battery voltage levels are measured by a microcontroller that calculates the duty cycle to achieve a desired output power.
The designer describes the problem thus:
Lithium-Polymer batteries provide enough power, but cannot be used directly with halogen lights. A two-cell LiPo battery (nominal 7.4V) provides about 8.5V when fully charged, and it is not allowed to be discharged below 5V. Halogen lights are commonly designed for 6V or 12V and their light power is controlled by the provided voltage level. While an 8.5V voltage level can overheat and destroy a 6V halogen light, the emitted light at 5V is very low. Therefore, a power controller is required that keeps the voltage supply constant for the halogen light.
A full schematic, firmware details and description of system configurations can all be found on the website. Check it out.
Features of the system are described as follows:
- Smooth transition between power levels.
- A remote control with a single button and an LED that can be attached for example to the strap of a bike pack.
- The button on the remote allows to turn the light on. It further allows to toggle between BRIGHT and DIMMED power mode. Holding the button for a second turns the light off.
- The control LED warns about low battery or when the light is not connected. Also, holding the input button when the light is off triggers the LED to show the battery voltage level.
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