DIY LEDs - The write-up

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It's fun to do some of these things differently, even if there's a way to say that something about them is not the very best ie efficiency. I'll be interested in how thermal management goes for you.
 
I am thinking of getting a par meter. But I found this thread
Has anyone purchased just the sensor and hooked it up to a multimeter (I think a few of us have those). Rather than $335 maybe only $139 here, but does anyone know the conversion formula? I read on the above thread multiply by 5.

Thanks
 
I talked with Jeff Bingham (Apogee technical support). So yes you too can have a PAR meter for $139 dollars. The output is in millivolts and for every millivolt smultiply by 5 to get umol m^2 /s. If you order 20 they give you a 20% discount.
 
TheFishMan65 said:
I talked with Jeff Bingham (Apogee technical support). So yes you too can have a PAR meter for $139 dollars. The output is in millivolts and for every millivolt smultiply by 5 to get umol m^2 /s. If you order 20 they give you a 20% discount.
Click to expand...

Just make sure you aren't using a cheap meter. Any error by the meter is multiplied by a factor of 5 so a 5 percent error in your 8 dollar Walmart meter will reflect a 25% error in actual PAR. The Yellow Box meter you get with their 350.00 deal isn't a real expensive unit but it is calibrated by the factory to have accurate readings. I just checked mine by the sun calibration on their website this morning. After at least 5 years since a calibration it's off by just over 10%, Pretty impressive.
 
I have a reasonable meter at home that I think will work. If not I will borrow a yellow box meter from the office. I will probably try several just to see. Any idea if it is the sensor or the yellow box that is off. Of do you have a full unit?
 
So my light was originally set up with 52 XRE Royal Blue, 8 Warm Whites, 6 Cool Whites and 18 XPG cool whites, all in series.

If there was ever any doubt about how much more efficient the XPG is, I removed 9 of them and added 4 XRE Neutral Whites and 5 420 Violets. PAR dropped from 140 to 91. YING!!!

Also took a reading after they had been on about 5 minutes and checked again after about an hour. With the heatsink at full temperature PAR increased from 88~89 to 90~92
 
TheFishMan65 said:
I have a reasonable meter at home that I think will work. If not I will borrow a yellow box meter from the office. I will probably try several just to see. Any idea if it is the sensor or the yellow box that is off. Of do you have a full unit?
Click to expand...

Mine is a complete unit they made. The meter isn't anything special but the difference is they calibrate it at the factory. Once you get yours hooked up they have a procedure on their website for checking the calibration using the sun. You could take readings at a few different times during the day to see how accurate your setup is, say 10 2 and 4. The site takes into account time of day, day of year, temp, humidity, elevation and location to come up with a theoretical reading you should get.
 
TheFishMan65 said:
I have seen that sight, but thanks. It sound like the probes are calibrated somehow also since it is a fixed value per millievolt.
Click to expand...

The probe is constant but if the meter isn't accurate it wont matter. If it reads the probe's 15 milivolts as 13 you get an inaccurate PAR value. When the calibrate at the factory they adjust the meter to match a given output from the sensor it should be reading.
 
I'm just about to finish gathering all the parts for my build. I'll be running 72 LEDs on 3 MW 60-48Ds (2 strings of 24 x 3). My questions have to do with getting the right resistors and fuses. Does 1 ohm resistors and 1 amp fuses sound correct? If that's correct, I need some help with finding "the" fuses. I've looked on digikey and was a bit overwhelmed by the selection - could one of the experts recommend a specific fuse for the job?
 
Generally speaking, are ppl still thinking a 60/40 ratio still seems like a good mix, even when using XP-E RB / XP-G CW/NW? Thanks.
 
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I think that is the opinion but I have seen some going 2:1. Which is almost the same 67:33. IIRC I did see one person considering 3:1, but I think that was a work in progress and don't remember what the final decision was. Sorry no personal advice I bought back in when XR-E were the way to go - just a long time to finish the fixture.
 
I can't speak on behalf of everyone else, but I can say two things:

1) For my next build I had been thinking for a while that I would do 24 RB and a total of 12 mixed neutral & cool white XPG. Now I'm increasing that to 24 RB with 12 each of neutral & cool white XPG, purely so that I have the option of individually dimming the neutral and cool separately, as well as better color blending.

2) Don't let the E in XP-E fool you, it cranks out 500 mW of royal blue radiation when you feed it 1000 mW of electricity. That's turning HALF of the electrical energy into photons, also known as HARDCORE.
 
Led

Led

Yep, i decided, i`ll be using the XR-E RB and the XM-L White on a 3:1 ratio with 144 LEDS. If something DOES come out newer during the build process i`ll still have an easy option to upgrade the plan then too. For the forseeable future though, this is what i`m doing. As i kick this off, i`ll post some pics.

PS: In case you ever woundered, in my Avatar, i`m the one with the Blue Helmet heh :) and those were only class 3 Rapids on the Hudson River.
 
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