Hello all,
Here's a simple project for a change. I've had a Black Diamond Cosmo (2013) headlamp for the past 6-7 years or so, and it was starting to show its age. I decided to do a swap of the emitters.
The main emitter was an older Luxeon Rebel LED, and it also had two auxiliary white LEDs, and one Red one (5mm and 3mm-dome type LEDs).
I was hoping to take advantage of the some the big luminous efficacy gains in LED technology over the past few years to improve this headlamp, which was otherwise still functioning very well. No change was made to the driver electronics.
Taking the flashlight apart, you can see the main LED mounted on a black PCB. I'm not exactly sure but it looks like an older Lumileds Luxeon Rebel LED.
For the replacement LED, I decided to go with a 80CRI 4000K Samsung LH351B.
The choice not to go to 90CRI was a trade-off between lumen output and colour rendering. For the use case, I felt that a brighter beam would be more useful than a better CRI one.
For the auxiliary white LEDs, I didn't like how narrow-FOV the original one was, and it had a sickly cool-white colour, so I swapped them out with some warm-white, very wide viewing angle 5mm LEDs.
Finally for Red LED, it suffered from the same issues (too narrow hotspot, and very bad optical artifacts), so I swapped that out for a photo red 660nm Cree XPE2. Now this turned out to be not the optimal choice due to mechanical reasons, but it's still better than the original in terms of usefulness.
A simple PCB was designed.
And above shows the final result after rework of the PCB. Time to test it!
Here are some beam shots for before and after comparison. The camera settings (ISO, shutter speed, temperature and aperture) were kept constant within sets.
For the main emitter, I was much happier with the increased lumen output (>50% more luminous efficacy), better tint (much better at 4000K), and better CRI, all while at the same drive current. This was a big win!
For the auxiliary emitter, you can see why I thought the original LEDs were not very useful. The new warm white ones produce a very nice, wide, glow - perfect when in a small dark space, such as a tent, where a wide FOV is preferable.
Finally, the red LED. Due to the low drive current, it wasn't as bright as what I was hoping for, but part of this was also due to the fact that the LED was recessed deeper inside the optical cavity. However, it still proved to be sufficient during my main use case for astronomy sessions, and I no longer have the annoying optical artifacts.
Here are all 3 different modes in operation. Both white modes are dimmable.
I know that this is a very old headlamp and there are plenty of new, much better headlamps available, but this was still a fun, simple project, and breathed a new life into my old 2013 BD Cosmos.
More details can be found here: https://www.loneoceans.com/labs/cosmoheadlamp/
Thanks for reading!