Alright guys, sorry about the long wait. I started working at a new job on Monday so I've been a bit busy. But I'm so happy I got everything built last week
So I'm an engineer and I really like planning everything, I did the cost analysis of doing 8, 10, 12 or 14 led bulbs. Either XML, XPG, bridgelux, even the cheap china bulbs. I was trying to get the most amount of light for the cheapest price. I did most of the calculations on this Google spreadsheet
I learned a lot during my research. I had just taken Principles of Electric engineering, thermodynamics, and programming so I knew the basics of wiring circuits, programming arduinos and a little bit about heat transfer. So this summer I decided to jump on the wagon and build the fixture. A big thanks goes out to Samamorgan
for the Led lighting Compendium
he created. Hoppy
for the excel sheet he created to calculate the PAR at the bottom of the tank. Schneeball
, Algae Beater
, and Raidendex or Michael
for all the info they gave me on their own LED fixtures.
Since Raidendex lives nearby I kind of used him as a guinea pig for building an LED fixture over his 120 first. I used his mistakes to improve my design.
The first thing that was really important to me was the efficiency. At the time I was using 4 55w compact fluorescent bulbs over the 40 gallon and had them arranged perpendicular to the front glass. It did a good job of growing everything but it would be awkward when only two of the bulbs were running. Either half the tank was in shadows or the whole tank was fully lit. When I ran all 4 bulbs over the tank I would always end up with algae. Since buying 4 new bulbs every year would have added up and the fact that they weren't lighting everything evenly just pushed me more to try the LEDs.
The second thing was that I wanted it to be bright! I'm trying to grow plants like L. Pantanal and erios and I already had the CO2 and fertilizers. I really liked the t5ho fixtures for the 36" but the price of buying the fixture, bulbs, and energy cost would have been too high over the lifetime of the fixture.
I used two major websites to help me out. ledgroupbuy
, they had little FAQs and guides that were very helpful. The Cree website itself had all the specs of the bulbs and I used a lot of those to calculate the average light output. I really wanted to keep the fixture simple so I set up a circuit with the leds in series. The driver selection was a bit difficult but once I understood the forward voltage*current*number of leds= watts needed from the driver it all came together. I didn’t care too much about dimming the LEDs, my dream tank is a 120 gallon tank so when I get that I’ll invest in a dimmable driver. If everything was too bright then I would just raise the fixture.
Using the spreadsheet I realized that the cost would significantly increase going from 10 leds to 12 leds since I would need to use multiple drivers. Keeping it low cost and simple I chose the 10 led set up. Roughly it would have given me 81 PAR at 20 inches which put me in the high light range. 12 leds would have given me 113 PAR but I didn’t want to spend the extra $50 and turn the tank into algae heaven.
Rapidled had the cheapest prices around but they ran out of XML U2 lamps a while back so I had to wait nearly a month before they finally got some in stock. I would have ordered from ledgroupbuy but their shipping was a bit higher and the extra cost would have added up to $20 more than rapidled.
Once they finally got some bulbs in I placed my order coming to $128.90 , ordered the 40 degree optics from ledgroupbuy for $31.95 and then ordered my heat sinks which I was able to pick up locally for only $21.57 I went out to home depot and got 8’ of primed linear 2-1/2”x1”, 13’ of thin aluminum wire, 2 hooks, 2 sets of wire graspers and 1 snickers bar (most important part of the build) for $12.66.
Together I spent about $177.02 on the actual materials. On the side I spent about $100 extra getting a multimeter, 60 W soldering iron and a dremel tool kit which I used to build, test and assemble the fixture. I didn’t count that in the cost since I needed that stuff anyway for other DIY projects.
Sorry, it’s so long, just wanted to give a bit of background info. I’ll post the build pictures on the next post.