Friday, August 5, 2011

Lights, and lighting.

I have always liked flashlights. When I was a kid I'd wire up extra batteries, and see how bright I could make a bulb. I also had a small collection of maglites, mostly the 3D size stuff. Given the time, and technology, it was about the best one could do without actually carrying a billy club.

Riding bicycles at night requires headlights. Simple? eh?

Well, not so simple. Bicycle headlights are expensive. Very expensive. And i'm a cheap bastard. Also, the cheaper lights tend to be incandescent. Which means 90% of the power will be radiated as heat. That's just not ok in my eyes.

The first headlight I bought, came with the taillight I have on my LT1000. It was (and still is..) a EL120 from Cateye. It's really not safe at any speed more than six or seven mph in the dark. Soon that was followed by a EL210. Which had 5 LEDs. And that actually is a useful light.

I did some research, and found the cheapest (electrically) way to make light is to use LED's. And the cheapest way to make power to drive the leds is with a switch mode power supply. (SMPS) I ended up buying the cheapest per-lumen leds I could find. I ended up building a national semiconductor simple switcher based circuit to drive them.

I was so proud when that little breadboard test worked.

The whole schebang was wired up on some perfboard, and made to work. But I made lots of mistakes, and I couldn't come up with a satisfactory mounting method. In the end I had 60 led's on perfboard with a PSU, and a grid of resistors to make them not burn out. Pretty terrible really.

Soon I learned of dealextreme. And I ended up buying some flashlights through them. the first ones were some AA "lock blocks."powereed lights. And I would attach those to the bike using something called

The choice of AA's was in a large part due to my desire to use normal batteries in the flashlights. And I had a decent stockpile of NiMh batteries to throw in them. The flashlights I bought were claimed to be "3w." Later, when I got my new flashlights, I found that they were only actually drawing 1.2watts.

They were just fine, and so long as I had two of the flashlights going, I was feeling pretty safe riding up to 15mph or so. But as I got faster, 15mph didn't cut it. So I started searching.

I think the big thing that made me buy into the 18650 size flashlights was the fact that I had a laptop battery with a dead controller board in it. The cells were all just fine, so I knew I could scavenge them. Around that time I was also just starting to get "ok" with LiIon cells. (I still distrust them on a certain level. I don't like cells that can catch fire.)

I took the plunge and bought a set of WF-502B based lights from Dealextreme. They claimed to be 250lm. These were the brightest things I've ever had my hands on. They were supposed to be a little more than twice as bright, but these things leave streaks across your vision if you look at the spot of light when shone at a desk! The kicker, is that they actually draw 4.2 watts!

Where I needed both lights going to feel comfortable with the older AA powered flashlights, just one of these 4.2 watt flashlights leaves me feeling warm and fuzzy while riding at night. Even up to 20mph or more.

This little setup has served me well for the last two years. Lots of light, and lots of battery life. A 2500mah 18650 LiIon cell lasts a little more than two hours.

No comments:

Post a Comment