garage LED lighting project

[Brian_H]

I'm remodeling my garage and turning it into a shop. The insulation and drywall has been put in, and I have taken delivery of a brand new Haas mini mill:







The lighting array I intend to install will consist of thirty custom made fixtures, each containing six Nichia 219's for 180 leds in total, powered by three 95% efficient meanwell 320w drivers, hooked to a dimmer.

The appeal of the Nichia NVSL219AT led is that it is 92 CRI, so it reproduces colors very accurately, including red, which leds typically render very poorly, and also the particular version I have is a quite neutral 4500k color temperature. Typically, high CRI led's are only offered at lower color temperatures such as 2900k to 3500k, which is a much yellower light, similar to a low wattage incandescent bulb. The Nichia 219 is quite special indeed. It's maximum recommended operating current is 1500mA, and it will approach 3.7 volts at that current.

Each of the 320w Meanwell drivers will power 60 leds, in 12s5p configuration, with each led seeing roughly 1340mA. The fixtures will feature a frosted diffuser that has 70% optical efficiency. The overall output of the luminaries after diffuser losses will approach 40,000 lumens and should achieve a lux of over 640 at full brightness. Total system power will be approximately 930 watts. (180x4.7 /.95)

The fixtures themselves will be made of rectangular aluminum tubing, 1"x3"x.125" in size.







To fit the diffusers to the tubing I will need to mill a couple of small channels along the 1" side. The angled portion at the base of the diffuser will wedge into these channels, and I will use screws to secure the diffuser to the tubing.





I have done some number crunching to get a rough idea of the thermal performance of these fixtures: the Nichia 219A has a thermal resistance of 7 °C/W typical; the MCPCB stars upon which the leds sit add 3-5 °C/W, achieving 12 °C/W worst case in combination. The profiles provide 19 in² of vertical surface per led plus some horizontal surface and also I will leave the ends somewhat open, but at 19 in² of vertical surface the heatsink will have a TR of 5°C/W, so the total additive TR is 17 °C/W. If the led consumes 5 watts, 4 of which are heat, the total temperature rise over ambient will be 68°C. The hottest it's going to get in my garage is 30°C, so the maximum Tj temp will be 98°C. I doubt I will actually be driving these suckers at full power very often, so they would typically be much cooler. At 600mA per led (1.6W of heat) there will be 360 lux in the shop space and the led junction temperature in 30°C ambient would be 57.2°C.

The maximum allowable Tj of the led is 150°C so this fixture should keep it well within operating specs. I will have to take some actual temperature measurements of the setup to more precisely determine the Tj of the led, but I am pretty sure these fixtures will allow for adequate cooling in the worst case operating scenario.

What I have left to do is model up some "end caps" and mounting brackets for their attachment to the aluminum extrusions, then do all of the machining and assembly, then all of the wiring and installation of the fixtures themselves in the shop.

I have actually been idle for a couple months now and need to get this project going again!