Date: Thu, 25 Mar 1999 10:08:39 -0500 (EST) From: Marty Goodman MD KC6YKC Subject: general answer to a lighting question Message-id: <01J98RY2WJKO9CJ3QU@delphi.com> Your many questions could easily require a book... or several books... for complete answers to be provided. Some of the answers to your questions might appear on the BikeCurrent mailing list. I've time here only for some very quick comments: (1)Incandescant Lights and beam-shapers Of course, the efficiency with which the transducer (light bulb, in this case) converts the electrical energy into the kind of energy you want (light) is very significant. All except ONE bicycle light currently on the market use incandescant light bulbs, and most use halogen varients of incandescant light bulbs. Among halogen incandescants (and actually among all incandescants) efficiency is (a) limited severely by the simple physical nature of the incandescant light and the principles of black body radiation that govern it (b) profoundly affected by what choice of compromise in the inverse relationship between applied voltage vs bulb life the system designer (or user) chooses to make and (c) affected significantly by issues related to the reflectors and lenses used to shape the light beam. The two commonly-used and good technologies are MR11 light bulb + reflector systems (NiteRider, Night Sun, Turbo Cat, CygoLite, BLT, Night Hawk, and many others) and separate bulb plus reflector and lenticular beam-shaping lens (CatEye HL500 2 Micro, Lumotec headlamp, old Union generator headlamps, CatEye NC 200 and NC210, and others). Non-imaging optics are beginning to be used in some bicycle ligting sysetms. Specialized WAS going to introduce this technology for a lower end headlamp (the Vegas) but pulled that technology just before the product was introduced because the final result could not be made quite cheaply enough to suit marketing pricing goals. The most significant development in increasing efficiency and utility of lighting systems commonly available at reasonable prices is the Willie Hunt pulse width modulator voltage regulator (LVR) device. This has not QUITE yet found its way into commercially avialable systems, but cyclists and mountaineers and cavers who are knowledgeable tinkerers have been using it for many years now, and it GREATLY improves overall performance and utility of lighting systems, especially those that use alakaline batteries with incandescant light bulbs. Willie's thrid generation LVR3 may find its way into mass production and consumer devices. We'll have to see. (2) Gas Plasma type lights Only one product so far among commercial bicycle lights incorporates a truly different technology for making light from incandescance: The CatEye Stadium Light (currently off the market, tho it may be re-introduced this winter) uses a metal halide (plasma gas discharge technology) light bulb and electronic ballast. This system overall is about 3 times as efficient in turning electricity into light, and the Stadium lamp, which consumes about 20 to 25 watts of power from its battery, puts out an amount of light equivalent to a 60 to 75 watt incandescant light bulb. Truly a dramatic improvement. However, the Stadium Lamp from CatEye as it currently exists has some problems: Great expense ($425 or more for the basic system), inability to run in a "dim, power-saving" mode (I and friends have modified ours to include this), bulb life harmed by the light being turned on and off many times, slow start up... 15 seconds from switch on to full brightness, and ten seconds from switch on to useful level of brightness. Some of these problems in theory can be fixed in future designs, I'm told. Others (such as the high price) may never be resolved. Note that for the immediate future, LEDs will NOT offer a viable means of technology for "to see by" bicycle headlamps, even tho they are improving greatly in the direction of being ABLE to be used in that fashion, and even tho already they CAN be used that way for caving and other lower power lighting applications. ---marty