All 8 strips of the cool white LED tape are installed, and tested. They all light up fine, but the PAR is not linear vs the number of strips, which it should be. Instead of getting 2X the PAR with 8 strips that I get with 4 strips, I only get 1.45X. That means I am short of PAR at the distance where I want to use this. A possible reason is that the current is less with all 8 strips than it was with 4 strips. I have read that the best way to hook up a long strip of LEDs like this is to apply the power at both ends of the strip - connect the + voltage to the + terminal at both ends, and the same with the - voltage. That will be the next test. It will improve the output if it is resistance of the long wires in the tape that is reducing the current.
At 20" distance - 40 PAR
At 23" distance - 31 PAR
At 25" distance - 26 PAR
At 35" distance - 14 PAR
I added wires to the other end of the strips, so the power is fed from both ends of the combined strip. It did raise the PAR substantially!
At 20" distance - 47 PAR
At 23" distance - 37 PAR
At 35 1/2" distance - 18 PAR
The increase in PAR with more strips still isn't quite linear, but it is a lot closer to being linear. And, this is still lower than I want it at 34" distance, where I want to use it. I could lower the distance to 32", and would get about 25 PAR, which is close enough to my goal of 30 PAR. Possibly that will be increased a bit by the 2 red and 2 green strips, which are the next test to do.
Last edited by Hoppy; 02-08-2014 at 10:35 PM.
Reason: Add data