LEDs for Bicycle Front Lighting
Cyclists who only occasionally ride at night may opt for an inexpensive LED front light and rear LED flasher. Red or yellow LEDs suitable for use as rear lights have been available for many years. Recently, white LEDs which satisfy the requirements for a front light have come on the market, and some jurisdictions have made or are considering making these legally acceptable. Very high-power LEDs are sensitive to overheating and over-driving, if the enclosure or driving electronics are poorly designed. Both of these conditions significantly shorten the LED’s lifespan, causing them to dim or completely burn out, and LEDs are expensive to replace. Most LEDs have a higher luminous efficacy than halogen lights, but poorly designed driving electronics can negate the advantage.
Low-power LEDs are adequate for riding on well-lit streets, but do not generally project a very bright beam as it is difficult to collimate the output from multiple LEDs into a single usable beam. This can be overcome by using a few very high-power LEDs – each with their own optics. It is now possible to buy LED equivalents for halogen rechargeable systems (including drop-in replacement bulbs), and LED lights for dynamos. On a dynamo, LEDs produce more light than halogen lights at very low speeds (down to 3 km/h according to one manufacturer).
High-power LED systems often include an option to dim the LEDs. LEDs are well-suited to dimming, as halving the brightness usually more than doubles the battery life. By contrast, halving the brightness of a halogen bulb only slightly increases battery life.
“Alien Eye” home built mountain bike light using standard MR16 5 W 12V LED Lamp
Efficiency is set to increase, as LED technology continues to follow a Moore’s Law pattern of exponential efficiency and cost improvements. As very high power LED lights become available and start to replace halogen designs, they may replace incandescent lamps whatever the power source, and will probably challenge HID lights. A 3-watt LED offers similar light output to a basic 10-watt halogen bulb – compare this with current generation “very high brightness” LEDs at 0.05 watts.
Advantages
- High luminous efficacy leading to long battery life
- Lifetime around 50000 hours of operation if current and temperature is managed
- Can be dimmed, usually with a slight gain in efficiency
- Instantaneous turn on/off and blinking
Disadvantages
- Limited light output per single LED
- High power LEDs require a constant current source
- Illegal in some jurisdictions
Low power LED lights are mainly for “being seen”, or as an emergency backup, and are the dominant choice for rear lights; higher power LEDs are now moving into the core market for illumination and are subject to rapid technical development.