> Slight hijacking of this thread, Be my guest. > Toshin Electrical have announced an LED based 20 - 24W fluorescent > tube replacement. Apparently the luminance is 370 lux at 1m below the > lamp. That rating makes it hard to estimate output. However - a linear fluorescent is amongst the most efficint types of lamp available. So lets assume that the original produced 80 l/W at 40 W = 3200 lumen. Assume that 70% of it gets radiated downwards typically (50% from tube and 20/50 = 40% or upwards light by reflection). A 40 att tube is 4 foot. 370 lux = 370 l/m >From the original tube along a 1 meter length of tube you'd get about 3200 lumen x (3.28/4) ~~~= 2600 lumen If this was radiated evenly in a half cylinder it would cove an area of half-circuimference x wdth = Pi x r x 1 = 3.14 m^2. So l/m at 1 m from original tube is about 2600/3.14 = 830 lux. To allow the LEd tube to be as good ALL the fluro energy would have to radiate euqlly over a full cylinder with no reflector. That result is so damning that it's worth trying again a different way. Original output as before 40 Watt x 80 l/W as before = 3200 lumen total output. Tube now radiates in a full cylinder. Tube length = 4 foot = 1.22 m Cylinder area at 1m distance = 2 x Pi x R x width = 2 x 3.14 x 1 x 1.22 = 7.7 m^2. Lux on cylinder surface = 3200/7.7 = 415 lux. SO the claimed light level is slightly below (~-11%) what you'd expect at 1 metre distance ANYWHERE from a fluro tube suspended in space. Place the tube in a sphere and you'd get down to about LED level. Best power LEDs at sensible prices are getting around 100 l/W. They are only about 25% more efficient than tube fluorescents. To halve the required wattage compared to a TF requires focusing the light energy by a factor of 2 x 4/5 = about 1.6X compated to TFs. Not a hard task. As for cost. 24 Watt of LEDs should cost well under $100. Any sort of volume should allow the end product to cost hardly more, if at all, than the LEDs alone in low volume. Main compettion with TF comes with improved lifetime. If it exists. Suitable quality LEDs are required. There are a large number of LED makers on earth, but arguably under 10 who know how to make an anything like leading edge product. The rest seem to have to be content with making inferior product or paying licence fees. By all means add to this list (in no particular order). Luxeon, Osram, Cree, Nichia, Agilent, Infineon, ?Edison?, ... There are a few more that don't come to mind but probably know well enough. I have heard several Taiwanese & Korean companies mentioned as having what it takes, but whether it is so and/or whether they achieve it through licensing the technology I don't know. A large and apparently capable Indian LED manufacturer (MIC Electronics) is apparently greatly boosting thei LED production capacity. Quality unknown at this stage. Philips are apparently starting LED manufacture in India. Relationship if any to MIC unknown. Russell -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist