My Rides

Sunday, September 11, 2011

Congrats Henry and Camile

A good friend married a great girl!  And little did they know:  there was another ninja in attendance!

Saturday, September 10, 2011

Bike Light - The assembly

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With a plan, a set of forstner bits, drill press, band-saw, belt sander, and files I set out to craft my light housing. As I mentioned before, the housing would be made from a PC Northbridge heat-sink (top, right), and about 2" x 2" x 3.5" piece of aluminum (whats remains, top, left).

I'll call the 2 primary pieces of the housing:  the mount, and the heat-sink.  The PCB (printed circuit board), with LEDs and driver circuitry, lens, and o-ring are sandwiched between the mount and the heat-sink - with the mount in front of the light, and the heat-sink to the rear.  I don't use any glue or fasteners to hold the PCB to either the heat-sink or mount.  The heat-sink is fastened to the mount, with 4 screws, and the PCB, lens, and o-ring are compressed between.

A shallow recess is bored into the heat-sink to locate the PCB and lens with a 7/8" (22.2 mm) forstner bit.

The mount is bored from the rear using the same 7/8" (22.2 mm) forstner bit.
The total depth of both bores is a little smaller (<0.5 mm or 0.02") than the total stack-height of the PCB, lens and o-ring.  So, when the heat-sink is fastened to the mount, with the 4 screws (4mm), the o-ring compresses, and the force keeps the PCB pressed to the heat-sink and the whole assembly from rattling.

It would have been nice to have a little tighter bore - 20-21mm (25/32"-13/16"), because the PCB & lens can shift around a little while trying to get things centered and the screws tight.  Home Depot didn't have a great selection, so it's a little roomy.

Before assembly, heat-sink thermal grease is applied between the PCB (which is on an aluminum substrate) and heat-sink, and also between the heat-sink and mount.  Note that care has been taken to make the mating surfaces between the heat-sink and mount as flat as possible (carefully filed) to maximize heat conduction.

The first time I put it together without any thermal grease between the heat-sink and mount, and it felt a little warm after riding.  With thermal grease between, it was cold after riding.  I'll do a stationary test, and see what the surface temp gets up to, but it may be that I could make the whole thing a bit smaller (less heat-sink area) without any thermal issues.

I've gone on a couple of rides, but I'll save those impressions, and some pics of the trail at night for another post.  For now, I'll just say "Wow!"

Thursday, September 1, 2011

Bike Light - The Parts

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This bike light has turned into it's own little hobby.  In addition to the high output bike light, I also have a lower output helmet light in the works, using:
  • LED:  Single Cree XP-G Q4 - warm white (3000K), on star board (, $6.25)
  • Driver:  5-mode, 1000mA "3 x 7135" (IC) based, 3-4.5V input (, $3.19)
  • Lens:  Various 20mm TIR lenses (, $1.25 ea)
I pick up my Lux-RC integrated light/driver from the post-office in the morning.  Arriving later this week are:
    • Battery Holders:  (2) 2 x 18650 Li-Ion battery holders (, $3.80 ea)
    • Batteries:  4 x 18650 Tenergy protected Li-Ion cells (2 cells, in series, for bike light, 1 or 2 cells, in parallel, for helmet light), with 2-channel charger (, $46.99)
    Also pictured:
    • Aluminum for housings, prototypes:  2" x 2" x 12" Aluminum Square Bar (, $21.73)
    • Heatsink:  The Northbridge cooler from an old PC