## Monday, November 19, 2007

### sub-$40 bicycle light As LED technology makes large advances, I decided to see if a simple LED flashlight could serve as a bicycle light. Bicycle lights generally fall into two categories: some only allow you to be seen (red or white, serving as tail- or headlights, respectively), while the more sophisticated ones allow you to see, illuminating the road ahead. Since LED lights are quite powerful at this point, I want the latter kind. Before buying, I set up the following constraints: • price: the light has to be below$40, the cheaper the better. I already have a pair of lithium-ion powered Dinotte lights, the front rated at 200L, I just need something to serve as a spare or when I have guests who want to bike at night (of course I would give the guest my Dinotte)
• batteries: it has to take standard batteries, AA or AAA. Chargers and rechargeable batteries are cheap for these, while CR123 is expensive. Also, if I forget to recharge, I can buy these easily at a convenience store anywhere
• small form factor and light weight: I don't want to carry something bulky
I ended up getting a 3W LED flashlight from Cabela's, for \$20+shipping. The nominal output of these lights is 65 lumens, which comes from a single Luxeon LED. Without further ado, here is a picture of the output (widest setting): The picture was taken at 2m (6.5ft), with the following camera settings: 1/12s exposure, f7.1, focal length 29mm. I took care not to overexpose the photo. If you look at it with a photo-processing application like Adobe Photoshop or the Gimp, you will notice a faint illumination (ranging from 20% to 5% of the peak) even outside the readily apparent white circle. For comparison, here is the light of the Dinotte with the same settings: Of course, the difference is obvious: the Dinotte is rated at 200 lumens, and has a much nicer lens to spread the light wider. Nevertheless, I am satisfied with the flashlight's performance, especially considering its price. Now I am experimenting with different mounting options (Twofish lockblocks should be arriving soon), and will post my experiences.