The Rhodium Lamp
That's it - and it works just fine! The lamp shade warms up to only to 65°C - that will be fine for some 50.000 hours of LED lifespan. Some specs: each COB has 10Watt, light colour 5600K. I run it at 700mA, where it delivers 1100lm at a CRI of above 95. So that is 3300lm for the 30cm diameter nanoviv tube, what equates to 50.000 lux. Not bad. Costs - well, the official version would be 30€ for the lights, 30€ for the copper blank, 20€ for the power supply, so altogether maybe about 100€ - in the silver version ;)
Well... it's just the underside... The COBs were connected in series, placed with some thermal paste onto the squares and fixed with glue. In front the magnetic connector (an old magsafe jack) to get the lamp easily connected to the power supply. The lamp is placed onto three acrylic spacers on the top plate of my nanoviv.
Now, that is a much better looking heat sink - but would it sufficiently cool down the COBs to the desired temperature of below 85°C? For optimal heat transfer I had to get the chips absolutely plane on the convex underside. All attempts to get some plane spots without disturbing the top shape were - well, a desaster... (let`s blame it on the Tequila). In the end I soldered three copper squares of 15mm to the underside to take the COBs.
The blank was then cleaned and pen electroplated with silver. To secure it from tarnishing and scratches, I Rhodium plated the top side - and had a name for the new lamp ;).
I started with a copper round in 26cm diameter and 1.5mm thickness, and bended it to a concave shape to get a 12° angle for the LEDs (to later beam straight into the center of the nanoviv tube).
The Rhodium lamp
Problem with LEDs - much in contrast to the common believe, and to manufacturer's claims - is, that they get really hot - as hot as any other conventional light source of equal luminous efficacy. But in contrast to the latter, the LEDs cannot stand much heat - you will need some cooling to dissipate the waste heat, or the diodes will burn through within a few moments.
As I wanted a simple, compact and aesthetic solution, I chose not to use cooling fans or such, but to go passive cooling. Well, the options for sufficient convectional cooling weren't very encouraging - who would choose a tiny light source to just mount it onto some kind of Death Star? There must be another way.
The Rhodium lamp
Problem with LEDs, especially with COB LEDs is - much in contrast to the common believe, and to manufacturer's claims, that they get really hot - as hot as any other conventional light source of equal luminous efficacy. But in contrast to the latter, the LEDs cannot stand much heat - you will need some cooling to dissipate the waste heat, or the diodes will burn through within a few moments.
As I wanted a simple, compact and aesthetic solution, I chose not to use cooling fans or such, but to go passive cooling. Well, the options for sufficient convectional cooling weren't very encouraging - who would choose a tiny light source to just mount it onto some kind of Death Star? There must be another way.
I started with a copper round in 26cm diameter and 1.5mm thickness, and bended it to a concave shape to get a 12° angle for the LEDs (to later beam straight into the center of the nanoviv tube).
The blank was then cleaned and pen electroplated with silver. To secure it from tarnishing and scratches, I Rhodium plated the top side - and had a name for the new lamp ;).
Now, that is a much better looking heat sink - but would it sufficiently cool down the COBs to the desired temperature of below 85°C? For optimal heat transfer I had to get the chips absolutely plane on the convex underside. All attempts to get some plane spots without disturbing the top shape were - well, a desaster... (let`s blame it on the Tequila). In the end I soldered three copper squares of 15mm to the underside to take the COBs.
Well... it's just the underside... The COBs were connected in series, placed with some thermal paste onto the squares and fixed with glue. In front the magnetic connector (an old magsafe jack) to get the lamp easily connected to the power supply. The lamp is placed onto three acrylic spacers on the top plate of my nanoviv.
That's it - and it works just fine! The lamp shade warms up to only to 65°C - that will be fine for some 50.000 hours of LED lifespan. Some specs: each COB has 10Watt, light colour 5600K. I run it at 700mA, where it delivers 1100lm at a CRI of above 95. So that is 3300lm for the 30cm diameter nanoviv tube, what equates to 50.000 lux. Not bad. Costs - well, the official version would be 30€ for the lights, 30€ for the copper blank, 20€ for the power supply, so altogether maybe about 100€ - in the silver version ;)