Headlight build and comparisson

[tomv]

I've built myself a nice 10W led headlamp and did some quick tests. I spent quite some time doing wrong things, so hopefully this will be a useful recipe for those who are thinking to make something similar. Also here is a quick comparison with a bunch of other lights.

Background. I've been ridding with 1W Cateye headlamp that uses 4AA and it's miserable experience in spots where roads are unlit. But I liked the helmet mount, that I want to keep. Its really handy to look at the side of the road, or to get attention of the drivers who don't see you just by looking at them.

The helmet mount:

 

[tomv]

Now a comparison. All pictures are of the same view, taken with the identical camera settings but different lights on. Camera was set to f/3.5, 1/60s, iso 1600, 28mm equiv lens. So view is pretty wide.


1) 1W Catye Led. Very narrow angle of view and pretty much not much light at all

2) 3W MR 16 bulb. This one is really pretty good. For $20 you get good led, lens, robust case/heatsink and amazingly a pretty good buck converter. It works fine from 10 to 20V and draws consistently 3.6W. I'm not sure it's rated for 20V though, probably that's pushing it. This is the easiest option to build good led lamp, but for me they were a bit too bulky and voltage didn't quite fit my batteries.

3) My custom 3 x 3W led build. Details in next post.

4) 55W automotive halogen light. Amazingly not much better than 10W led. It gets too hot to touch in seconds.

 

[tomv]

Now for the 3x 3W light build. Parts are:

3x 3W white star leds
2x 10 degree lenses
2x 30 degree lense
PowerPuck buck converter
Milwaukee V18 lithium tool battery
3mm x 25mm aluminum bar
1mm think aluminum foil
Heat sink grease
Assorted wires and screws

The key to making it work is heat sinks! I only got it acceptable on the third try. First try was out of stainless steel - not good. Case remains lukewarm and leds get too hot real fast. Just mounting leds on aluminum bar works great. Heat gets transfered so well that there's not much difference in temperature of the parts. LED is about 90C and the bar about 70C - too hot to touch. Adding the foil makes it reasonable at 50C or so - still possible to hold it in your hands. Outside in winter the warmth will actually be pleasant.

I've decided to use Milwaukee V18 batteries as they are easy to use, fast to charge, should last a long time, etc, etc. PowerPuck will work for up to 32V, for more than that you'll need a small DC/DC convterter.

 

[tomv]

Next steps will be to waterproof this one and to build rear light out of red 1W leds.

I'm undecided if I should use lenses for them or not. Should I keep leds covered with clear or diffuse glass? The goal is to achieve maximum visibility. Any ideas?

 

[TylerDurden]

Nice work.

Perhaps a lens/bezel that has a clear face as well as a diffuse perimeter visible from the sides. If you travel at speed, you want ground illumination well ahead of your rig.

 

[tomv]

Side illumination now is surprisingly good, similar to the halogen car light. Lens rated for 30 degree angle actually throws lots of light to the sides too. I'm not sure how they rate them.

The problem with doing a nice closed case is heat. Even now, everything open, heat is borderline unacceptable with 10 watts of power. Now I'm seriously thinking of using aluminum CPU or motherboard heat sinks as basis for version 2.

 

[TylerDurden]

The diffuse perimeter would be for visibility by other vehicles at positions up to 90 degrees from line-of-travel. Taillights on autos that wrap around the corner of the fender are designed in that manner: central focusing lens facing in line with travel, diffusers at the periphery for visibility from the side. ( Eliminates the need for additional side marker lights at the rear.)