Bicycle lighting: Encyclopedia II - Bicycle lighting - Front lighting

Bicycle lighting - Front lighting

Bicycle lighting - LEDs

Cyclists that ride at night only occasionally might 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 or are considering making these legally acceptable. Very high-power LEDs are sensitive to overheating (e.g. 5W Luxeon Vs), and over-driving, if the enclosure, and driving electronics are poorly designed, both of these conditions result in significantly shortened lifespan (dimming, or complete burn-out), and the LEDs are expensive to replace. Efficiency of the LEDs in lumens/Watt is superior to most halogen lights, but the driving electronics can eat up all of the advantage unless well designed.

Most riders will use alkaline cells to power inexpensive LED lights; these can have a life of anything from under a week to a year or more depending on the amount of riding, and brightness of the LEDs - life will be longer in flashing modes (even though many lights make the LEDs brighter when flashing than when steady to conserve battery life).

Low power LEDs are adequate for riding on well-lit streets, but they 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 small number of very high power LEDs - each with their own optics - and it is now possible to get LED equivalents for halogen rechargeable systems (including drop-in replacement bulbs), as well as LED lights for dynamo power - Solidlights offer a range, as do NightLightning, Cateye, Busch & Muller and others. One particular advantage of LEDs in dynamo-powered lighting is that they produce more light at very low speeds (down to 3km/h according to one manufacturer).

High power LED systems often include a option to dim the LEDs. LEDs are very well suited to dimming (running at half brightness will normally give you more than double the battery life), unlike halogen lights, where running a single bulb at half brightness will only give you a slight increase in battery life.

The adoption of high-power LEDs by the commercial lighting industry and automotive industries is driving prices down and brighness up all the time. Efficiency is also set to increase as white LEDs switch to emmiting Red, Green and Blue light to form a white output (current designs use a blue LED, with a fluorescent coating, much like conventional strip lights use). As very high power LED lights, such as the Lumileds Luxeon range become available and major manufacturers start to adopt these high power LEDs to replace their halogen designs (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), there are grounds to believe that LEDs will replace incandescent lamps whatever the power source. In the future they may even challenge HID lights.

Advantages of LEDs

• Can be cheap
• Long battery life in flashing mode
• Can be very visible
• Efficient
• LEDs last pretty much indefinitely (as part of a well-designed light)
• LEDs can be dimmed, usually with a slight gain in efficiency

Disadvantages

• Limited light output, especially in steady mode for many models
• Some models do not run as long on rechargeable cells as on alkalines; environmental concerns
• Illegal in some jurisdictions

In general, then, 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 at present.

As with high-power halogen systems, high-power LED systems have attracted self-build enthusiasts, top-end commercial products tend to be similarly high priced - due to the relatively low production volumes for these high-end parts. Some examples - [1] [2] [3] [4]

Bicycle lighting - Low-cost battery lights

For occasional use a low-cost battery light such as the Cateye HL-500 can be a sound choice and usually meets legislative requirements. A complete set of halogen front light and LED rear light, including batteries, can be had for well under $20. These lights are low power but compensate to this to some extent by using surprisingly good optics. Some newer models are available with LEDs instead of halogen lamps; this is not legal in all jurisdictions.

Advantages of low-cost battery lights

• Low cost
• Easily moved between bikes
• Readily available (both lights and batteries)

Disadvantages

• Cost of batteries
• If using rechargeable cells, limited burn time
• Generally low power

In summary, then, a standard halogen light can be a good choice for the less demanding occasional user. It can also be a useful emergency light if your usual lights are more exotic.

Bicycle lighting - Rechargeable Flashlights

There are some high-power flashlights, with rechargeable lithium-ion batteries. Although not specifically designed for bicycle use these are a viable alternative to rechargeable halogen lights, though they are still expensive (US$80). They can be fastened to the bicycle handlebars with a device called a "Lock Block." Look for a flashlight that has an adjustable spot to flood beam. These are sold by police supply stores, under the Streamlight brand. Although the optics of these flashlights are generally high quality they are still rotationally symmetrical (unlike motor vehicle lights).

Advantages of rechargeable flashlights

• Versatile - can also be used as a flashlight off the bike
• Portable, so theft resistant

Disadvantages

• Limited burn time
• Heavy (rechargeable systems generally separate the weight of the battery from the lamp); weight may be an issue for off-road riders due to vibration
• Optics not optimised for road use

Bicycle lighting - Rechargeable Halogen Systems

Although these lights were primarily designed for off-road use, where they are almost universal, many commuters and transportational cyclists now choose to use high-power halogen front lights which operate from a NiMH, Lead-Acid, or Li-Ion rechargeable battery pack.

The lights used by most halogen rechargeable systems are cheap, bright but fairly unsophisticated: they project a cone of light (wide and narrow beam options are available) which is good for off-road use but not ideal for road use as it can dazzle oncoming road users. Road vehicle lights generally have beam patterns which are relatively flat, and most road vehicles are subject to legislation restricting the amount of light spilled above the horizontal axis. This also means that rechargeable halogen lights do not meet legal requirements in some jurisdictions.

Because they use standard commercial prefocused optics, a wide range of power and beam width combinations is available. Most systems allow simultaneous connection of different lamps - for example, a wide and a narrow beam for offroad riding, or a high and a low power beam for road riding.

Cost for these systems ranges from US$50 to US$200+.

Advantages of rechargeable halogen systems

• Bright, sometimes very bright
• Readily available
• Can connect multiple lamps to one battery pack; provides flexibility
• Reasonable battery capacity
• Very reliable
• Can usually be easily removed from the bicycle or to prevent theft
• Lamps are cheap, widely available, and come in many combinations of power and beam width

Disadvantages

• Relatively heavy battery
• Limited run-time between battery-recharges
• Hassle of being certain to keep batteries charged
• Batteries have limited life, typically 500-1000 recharge cycles
• Optics not optimised for road use

In summary, rechargeable halogen lights are the most common solution for offroad night riding, and increasingly popular for road riding due to their brightness, moderate cost and widespread availability.

Some cyclists build their own lighting systems with commercially available lamps, batteries, and chargers. For a person with the necessary technical background and workshop skills, this can be an enjoyable challenge. Hardware costs can be lower than equivalent commercial systems (although "intelligent" chargers can be quite expensive). However, some components are not typically available in local hardware stores, and time spent searching for suppliers should not be underestimated.

Besides locating appropriate batteries and chargers, the biggest challenge is attaching the lamps to the bicycle. Resulting systems often have a decidedly "homemade" look, relying on blocks of wood, pipe fittings, etc. for housings and mounting hardware. (See illustration above.) Many web sites have detailed instructions, including parts sources (search for: "build bicycle lighting systems" to find these sites).

Advantages of home built systems:

• Less hardware expense
• For hobbyists, the pleasure of designing one's own system

Disadvantages

• Necessity of searching for appropriate components
• Need for appropriate home shop tools and skills, both mechanical and electrical
• Construction time

Examples - External Links

• How-to build a halogen bike headlight with readily availble components

Bicycle lighting - Rechargeable H.I.D. Systems

HID lights are the brightest lights currently available for bikes. They are efficient, very bright, but comparatively expensive (US$250 and up). They also tend to have high power consumption, so a relatively limited burn time. Other than this they have the same advantages and disadvantages as rechargeable halogen systems, and like halogen systems they are designed primarily for off-road use, having rotationally symmetrical beams which cast as much light up as down.

If you use a HID lighting system on the road, you should be particularly careful to adjust your lights to avoid dazzling oncoming traffic.

Bicycle lighting - Dynamo Systems

Dynamo systems are probably the most widely-used worldwide, although they are uncommon in North America. They provide a self-sufficiency which is valued by their users: no batteries to recharge or replace, and permanently fitted to the bike so no worries about being out unexpectedly late without your lights. (Note: bicycle dynamos produce AC, and so are more correctly referred to as alternators or generators, but the word 'dynamo' has stuck in universal usage.)

Dynamos are generally limited to 0.5A output, nominally 3W at 6V, although 12V dynamos are available and the best nominal 6V dynamos can produce 6W at speed, as detailed here. A dynamo behaves as a constant-current device, not constant voltage; this means that the voltage can exceed the capacity of the lamp at speed, causing failure. Historically this was considered an inherent nuisance but these days lamps and dynamos often incorporate zener diodes to prevent it. In practice it is not an issue for most users as the electrical design of the dynamo itself tends to self-limit the output voltage at normal riding speeds. Good dynamos are extremely efficient and provide full output at surprisingly low speeds, often 4-6mph is sufficient for full brightness.

To compensate for their limited output, dynamo headlights have good optics which focus the limited amount of light in a narrow beam that lights up the road directly in front of the bicycle; this can be seen in Andreas Oehler's side-by side comparison of beam patterns. To compensate for the fact that dynamos produce no power when stationary the best lights (and some dynamos) have a stand light facility, usually a single blue-white LED powered by a capacitor which will run for around five minutes. It is now common practice to use all the dynamo's output to power the front light; the alternative is a 2.4W headlight and a 0.6W tail light. Most good dynamo rear lights now use LEDs instead of incandescent lamps.

Some riders consider the output of dynamo lighting insufficient. Others report that it is adequate to see on dark roads at speeds up to about 20mph (single 3W) or more if a 12V system is used. Whether the output is sufficient or not will be a personal choice based on the roads you ride and perhaps how good your night vision is. Around town the quantity of light output is generally less important.

Like most lights, dynamo systems range in cost from around $30 for a basic system to $250 or more, especially if you aim for 6W output. Hub dynamos are generally considered the best but require a wheel to be rebuilt if retrofitted (your existing rim can usually be reused). Some bikes are available with hub dynamo lighting systems as a factory option; this can be very cost-effective.

Cheap dynamo lighting systems are available both from bike shops and non-specialist retailers. These can be made to work quite well; simply changing the lamp to an halogen one will produce a big improvement in light output. As usual though, both efficiency and longevity tend to improve with price. At present the SON hub and Dynosys bottle dynamos set the standard by which others are judged.

Advantages of dynamo lighting

• Unlimited burn time
• Always there
• High-efficiency optics that are designed to maximize the available power for the lamp (optimised for road use)
• Reliable (although see below for issues with bottle dynamos)
• Environmentally friendly and cheap to run
• Unattractive to thieves

Disadvantages

• Bottle dynamos are noisy, can slip when wet, and wear the sidewall of the tire
• Without standlights, when you stop your lights are off
• Limited power output
• Cut out at very low speeds (below walking pace)
• Difficult to remove where theft / vandalism are a problem
• Cheap dynamos produce noticeable drag

The best dynamos come from Europe and Japan. Busch & Müller and Dynosys make higher-end systems; Marwi, Axa-Basta and Nordlicht offer some low-cost models. SON, Shimano and Renak Enparlite make hub dynamos. Head and tail lights are made by a number of manufacturers including Busch & Müller, SON, Hella and Axa-Basta. The SON E6 headlight has the same excellent optics as the highly-regarded but now unavailable Bisy-FL. This is available with and without a glowring (which is visible from the sides but can interfere with night vision if mounted on the handlebars).

Adapted from the Wikipedia article "Front lighting", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki