Wow. I haven't posted to CPF in years.
I've not been so interested in flashlights, but since I acquired a house I'm quite interested in fixed lighting - particularly LED lighting since it's getting more powerful and the lumens/watt and lumens/$ figures keep getting better. I guess I was inspired by the local 7-11's swapping all their outdoor floro and metal halide lighting for LED modules (I can't figure out who they're using - wish I could source some of those for a reasonable price).
I've never liked the driveway lighting for my house - it came with a dual incandescent flood fixture that produced two distinct spots
I happened across 3-up Rebel MCPCB's sometime in the third quarter of 2010 and immediately realized their potential for lighting bright enough to be quite useful singly or in groups. I obtained 6 while I waffled on how to power them - switching power supply plus resistors is cheaper, but less efficient than a fixed-current driver and requires significantly more fabrication.
I then came into possession of a pair of handy constant-current drivers and the plan was ready for execution.
I fabbed up some fixtures:
Triple-emitter is AAd to the holder, which is AAed to the mounting plate (2.00 x 0.125 aluminum bar); the holder is really a tiny aluminum sample container with a glass lid that wasnt terribly easy to frost with sandpaper (not pretty, but these were destined to be out of sight)
I hung some metallic raceway:
Out of sight from more than five paces, so don't give me any lip about them not being lined up; the other wire is pre-existing
After some frustration with popped solder joints, ripping a few solder pads off the MCPCB's, and the distinct pleasure of soldering something attached to the ceiling while standing on a ladder, I scaled back the design to 4 fixtures. I'm quite pleased with the results:
Cellphone pics are all I have. Sorry.
Each fixture should be sipping about 3 watts for 12 watts net. Figure in some driver inefficiency and I'm looking at maybe 15 watts total power consumption. Fewer absolute lumens than even one of the halogen lamps it's replacing, but the light is uniform and where I want it rather than two spots on each half of the driveway. Color is a tad cool, but not too far off from some of the CFL's in the neighborhood.
Learned a few lessons:
- My soldering skills need some work. Some serious work. The bigger the blob, the better the job is OK for through-hole components on a breadboard with generous clearances, not so great on surface-mount and other devices requiring far more attention to detail with a bit more heat sensitivity than a 2W flameproof resistor
- Strain-relief is important for solder joints, especially when your solder pad is little more than a trace on a single-sided PCB - I ruined 2 modules and a third is decidedly ... marginal (but working - nothing some RTE or liquid electrical tape won't fix whenever I decide to fix it ForReal)
- A dual-gang box is a lot smaller when you're on a ladder trying to stuff 2 power supples and a bunch of wires with slack connected with wire nuts into it than when you're test-fitting it at a bench
- Arctic Alumina has a tight hold, but it has limits
- Measure twice, three times, a fifth time, then screw something down
Not entirely sure how much it cost me in the end. Emitters were $17 each, drivers were $20 each, and the holders were $9/20. I didnt track all the other sundries (wire, aluminum bar, wire clamps, raceway, J-box, way too much solder, RTV, and too many trips to Home Depot). Obviously more than just getting a better off-the-shelf fixture from Home Depot...
Ill probably do some more of these again elsewhere, but will redesign the fixtures a bit. I imagine Ill just use thermal grease between the elements and just screw the assemblies together. Ill also find a way to strain-relieve the wire - maybe with a grommet in the holder or cable clamp outside.
I'm also interested in the Cree XP-G 3-up MCPCB's that LEDSupply recently released; they had previously only had XP-E in cool white, which I did not feel was acceptable for outdoor lighting.
I'm sure that some will point out that drivers and LED's are available on dodgy websites like DX for cheap. Trouble is that those sources are not known for high quality, timely delivery, nor could I count on their drivers being CE/UL recognized.
Anyway - I appreciate any feedback.