For people like me who still have old and inefficient COBs laying around. You can improve efficiency by driving them a lot softer. Doubling up the COBs can improve efficiency by 10%. My old CXB3070 AB bin COBs run at about 2umol/s/W at 1400mA. If id double them up twice, efficiency improves by about 20% and I end up at a more 2018 relevant 2.4umol/s/W
So I quadrupled the AB bin COBs, but I also had 16 AD COBs of which 12 were "3-upped" and the last 4 were "2-upped" (within constraints of what the two HLG-185H-C1400 drivers can deal with and the number of COBs I had laying around). In total 24 CBX3070's were crammed together on 4 aluminum bars. 6 COBs per bar spaced out according on their individual wattages.
I ran a simulation of the fixture over a 100x100cm area. At 5cm height (left) you can see the distribution of the 3 different wattages (8x11W,12x15W and 4x23W) and at 15cm (right) I feel the distribution is good enough to use:
View attachment 4111892 View attachment 4111893
The blue areas denote the areas where there is less than 80% of the average light intensity. ie the dark spots.
Some pictures of the fixture running it's first test:
View attachment 4111889
View attachment 4111890
In total this setup should produce 900umol/s (well up from the 780umol/s which the 8 CXB3070 AB bins produced) while power usage went down from 395W to 367W.
View attachment 4111878
Based on datasheet figures, the efficacy for the whole frame went up from 1.98umol/s/W to 2.45umol/s/W. Efficiency went up from 42% to 52%
Wiring this up was a bit of a nightmare due to all the different clusterings of COBs and the parallel wiring, but still, it felt a waste to throw away the old COBs and replace them by strips. I sort of made my own strips
I was a bit worried if the bars would adequately get the heat away from the COBs, but that seems to work just fine. COBs are running a lot cooler than they did before. Which of course also make sense since they are running much softer than before. That might also increase efficiency and light output a little pulling this new fixture even more ahead.
Wiring for the fans is still a mess, but I couldn't get myself to snipping off those leads. Wiring for the COBS could have been cleaner too, but I was glad I got it right the first time.
Metal wires for hanging it are ordered. For now the bit of rope will do.
I took some FLIR shots to check the temperatures.
The drivers are at around 34C. Somewhat less than before when I had them outside the tent. I placed them on the frame since I really need more heat in the tent anyway.
View attachment 4111880
COBs were running at 50C to 55C before (@48W).
15W at 36C:
View attachment 4111881
23W at 46C:
View attachment 4111882
All seems to be running fine, so I put some plants under the new fixture. Doing a test of nutrients specifically tailored to LED light. Sold by GPleds and created by Hy-Pro.
![[]D[][]\/[][]D](/data/avatars/m/985/985221.jpg?1521126417){kind=avatar}
