Katie Phibbs (The Lettuce People) did an excellent grow comparison between HID lighting, T5 lighting, and the Philips "Power Grow" LED lights.
I purchased several 5 foot Phillips LED lights for my hydroponic lettuce and they work beautifully.
At $175 each -- I wanted to see if I could make my own and save some money.
Without much thinking, I purchased 5050 led strings in red, blue, green, and white. I made a DIY grow light by getting a 2 inch wide strip of wood (8 foot long) from Home Depot and placed the 4 strips of LEDS side by side. Powered it up and was totally disappointed as it was no where near as bright as the Phillips' LED light.
I needed a way make light measurements.
I researched PAR (Photosynthetically Active Radiation) meters and purchased a MQ-200 from Apogee. At the time (Jan 2016) Apogee stated that their MQ-200 meter was excellent at measuring PAR values when measuring LED lighting. I got the PAR meter and started making test measurement between my DIY LED light, the Phillips LED light, T12 florescent lights, day light --- nothing made sense (Feb 2016). I went back to the Apogee site and found they now made a MQ-500 meter which addressed the lack of sensitivity above 660 nm the MQ-200 exhibited (little did I know when I purchased it).
A PAR meters provides a value of Photosynthetic Photon Flux, PPF, measured in units of Âµmol m-2 s-1 ---- for light between 400nm and 700 nm. The Philips LED light uses Deep Red LEDS at 660nm --- which was that the knee of the MQ-200 filter.
Apogee upgraded my MQ-200 to a MQ-500 for the price difference in the sensor cost. NOW I have decent PAR meter for doing LED lighting comparisons.
As an example --- the MQ-200 provided a PAR value of the Phillips light at 8 inches of 38. The MQ-500 provides a PAR value of 138 at 8 inches.
Note -- all PAR measurements below are done with the MQ-500 which measures light from 400nm to 700nm.
Philips recommends placing their Power Grow LED lights 8 to 18 inches from the top of the plant.
At 8 inches -- my Lettuce is seeing a PAR value of 138 (Âµmol m-2 s-1)
5 week old "Giant Caesar" in the back row and 3 week old "Baby Romaine" in the front row --- notice the deep red lighting.
My 4 color (red, blue, white, and green) DIY 5050 LED light turn out to be a major flop. PAR at 8 inches was 15 and at 3 inches was 44.
Second try -- little smarter now. Purchased a strip of 630nm (RED) 5730 LEDS and a strip of 470 nm (BLUE) 5730 LEDS. The 5730 produce more light output than a 5050. I made a quick test using 3 parallel lengths of RED and one length of Blue (Phillips uses a 3 to 1 ration - red to blue) -- PAR value at 8 inches was 10 and 3 inches was 50. Still a flop.
I gave up trying to replace the Phillips LED lights and turned my focus to the lighting I was using for my seedlings. I had started using a 24 inch T12 florescent light placed 3 inches above the seedlings but it produced plants that were thin and dwindly (long and thin -- stretching to get light).
I purchased a 6.6 foot length of grow LEDS from Amazon - $12: Wavelength: Red 625-660nm; Blue: 450-465nm
https://www.amazon.com/gp/product/B00WJZ ... ge_o02_s00
I cut the length of LEDS into 5 16 inch strips and placed them side-by-side on a 2 inch piece of wood to make a DIY 20 inch grow light.
The picture shows my DIY seedling grow light next to the Phillips Power Grow LED light.
I mount the seedling light on a home-made stand and position it 3 inches from my grow material.
At 3 inches -- the DIY seedling LED Grow light provides a PAR value of 95 (3 inch PAR value for T12 florescent was 36).
The DIY seedling LED light works wonderfully. The seedling appear and produce multiple leaves prior to transplanting with zero stretching!!! I could not be more pleased.
Just thought I'd share to save some flops from occurring to others that may be thinking along similar lines.