Hello all,
Back a while ago there was some discussion about LED lighting, and I built a ring light for my mill using a 39 LED 120 mm ring I bought on Ebay for $6. I was pretty happy with the way it looked, but I also took some measurements.
Using a 12V supply, I turned it on and measured a current draw of 200ma, well within the capability of the small wall wart I am using. Placing a light meter on the table of the mill and positioning the bottom of the ring 12 inches away, I measured the light intensity to be 546 lux with no other ambient light. This LED light does not get warm, it is almost impervious to flying chips, and provides a very even light without shadow. I don't know what the wavelength or black body temperature of it is, but it is pretty close to a cool white, not like some of the bluish ones I've seen that are called "white."
For comparison's sake, I took the same meter and placed it on the top of my drill press table, which uses one of those magnetic base task lights like http://www.harborfreight.com/75-watt-magnetic-base-light-90766.html I positioned the light source 12 inches from the bottom of the bulb to the meter, also with no other ambient light. A regular household white incandescent 40 watt bulb was 420 lux, a 60 watt was 912, and a 100 watt bulb was 1740. Therefore, I believe the LED ring light is roughly the same as a 50 watt bulb. Seeing as how I use a 60 watt bulb in it normally (A 100 is just too hot to work around) I am pretty happy with the LED ring. I suppose you could use this 120mm ring with another 180mm ring outside it and the combination would provide a 100 watt equivalent LED light if you felt you needed it. (The light meter I am using has a total error of accuracy of +/- 4% and an error in repeatability of +/- 2% with a resolution of 1 lux in the range I was in.)
Just for fun, I also measured a couple of CFLs. A 13 watt CFL (advertised as a 60 watt equivalent) turns on at 340 lux, but within 4 minutes settles down at 936 lux. A 26 watt CFL (advertised as a 100 watt equivalent) turns on to a measly 194 lux, but in 4 minutes is giving out 1290 lux, still a fair bit away from a incandescent 100 watt bulb.
Just thought I would share that data.
Happy Holidays, __._,_.___