From XP-Gs to XM-Ls to XP-Ls
While I have been working on many of my own projects as well as work full time I have not posted in some time so I started to look over the projects box and had a throw back. I have come a long way from Luxeon 1 LEDs and messy thermal epoxy. Looking at the projects I see where I have improved and where there is still room for improvement. Some of the common themes I saw were doing the things the hard way (machining copper instead of aluminum) and generally going overboard on heat sinks. While not necessarily a bad thing for bespoke applications, in production reducing manufacturing cost and time are top priority.
Flashlights continue to be a fun base platform to enjoy the newest LEDs. I have also been trading lumen output for better CCT and CRI/GAI light sources. After years measuring LEDs in integrating spheres I’ve seen that lumen difference is much harder to see than good color or even worse, bad color. This is usually the motivation for flashlight modification, I bought a new Surefire EB2 and the color was terrible, an ugly 6000K+ and it was very far above the blackbody giving it a terrible green look.
Copper is a fun metal because of its thermal properties as well as the feel. A good piece of copper weighs a lot heavy feels good when it comes to lights that you don’t have to carry. I feel good knowing that a copper heat sink will probably be over kill but that L70 of the LED living on it will be a long time. From machining solid bricks to folding sheet copper has been very satisfying to work with.
Above is one of my very early very thing and flexible boards I had made for the Cree XP series footprint. Because the copper on the pour was so thin I was not able to run much more than a few hundred milliamps so I switched to the ML-E series LED. I used these in a few projects but desired more bang for my buck and the XP series is almost the same footprint and could run at almost 5 watts.
Moving towards the higher wattage I have stuck to the Cree CXA/B series COB for higher output applications. Pictured above is a 2540 series in a 90+ CRI offering. This is part of a stage lamp retrofit, the heat sink is actively cooled and can comfortably run this package in the 30w range with only a ~20 degree C rise above ambient. More photos on this project to come when it is complete.
This is one of my first home lamps that I really liked. It was an indirect view lamp that used 6 XP-Es (like 4000K @ 80CRI min) in series run off a 350mA driver. They were mounted to a 3′ piece of aluminum with what is clearly an excess of arctic silver thermal epoxy for a part cooking around 1 watt. It was suspended from the ceiling by four wires, two power and two for support. I have since keep on the indirect theme but moved to warmer and higher CRI sources for a more comfortable environment.