Snorkeler's Cube

Finally, after almost a year between planning, prototyping, building and coding, my DIY LED fixture came to life. On Sept 6th the woodworking shop, LD Marcenaria delivered the new hood (they are very good, super recommend them to anyone living in São Paulo). It looked good, had dimensions according to the Google Sketch I had drawn, seems strong, etc.

Installation was way longer than just swapping the old hood for the new one because I had to redo the Aluminum structure of the fixture. I decided to elevate the LEDs and use tighter optics (15o and 25o), and the hood was made tall taking that into account, but, I couldn’t find time to redo the structure before the hood was delivered. That proved to be time and sweat consuming ... without a power tool cutting the aluminum was quite a workout . But nothing offsets the joy of seeing the thing working.

Well, if you've been following this blog you know it's an Arduino controlled, MOSFET driven, 12V 3LED lamp blue/white fixture, bla, bla, bla, so I won't repeat the details or this is going to get boring...

Time to see some pictures of the hood, fixture and important details.

This is the hood from the outside. It is rather tall, which I didn't like but got used to (but my wife liked it better than the old stout hood, go figure....).


This is the hood open exposing the lights and structure. I have A LOT more room to put hands/arms in and do tank maintenance with this hood. Simply loved that.


This is the hood from above, showing the plastic tupperware box with the Arduino controller. You can see how it is open, letting heat escape upwards and reducing humidity in the hood:


Here is a detail in the controller, manual override switches. The middle white switch defines if the drivers get the Arduino's PWM signal or manual white/blue full on/off signals. The other two switches are the manual white/blue full on/off switches (duh). This is handy for testing and for those moments when you absolutely need to light the tank up to full power.


This is a closeup of how I connected lamps to controller, using connector pairs. Red+Black are for the white lights, whilst Blue+Grey are for the blue lights:


This is a closeup of one of the lamps sitting on the structure. Notice I use plastic spacers to gently tilt the lamps inwards, so the light is better used. If I kept the lamps horizontal some of the light would hit the aquarium walls, which would be a waste.


Although the hood was "online" on Sept 7th it didn't work right until Sep 14th due to some bug squashing needed in my Arduino sketch.

In the final Arduino sketch I also merged in code that enables me to send serial commands through the Arduino development environment. That made it easier to force the controller into a certain weather profile for the day or set the date/time. This sketch is V-1-3-0, has a non-trapezoidal light curve that mimics the sunrise and sunset of the Great Barrier Reef, includes weather/cloud simulation (with “lightning” during “thunderstorms”) also based on GBR weather data. It is fun to watch. No moonlight yet, neither support for an LCD (which I haven't bought yet), those I intend to add one day in a future V-1-4-0.

I haven’t measured PAR yet, but I’m quite positive it is much better than before. A local reefer that has a PAR meeter agreed to come over and do some measurements, need to schedule that with him. I’m nor expecting super high SPS compatible numbers, but high enough for soft and maybe even LPS corals in some bright/tall spots.

I only have 8 “LED lamps” with 3x3W LEDs in each, which for a 3600 cm2 surface area (558 in2) is in the low range. I can upgrade the system to 12 “LED lamps” but in the short term I’m not looking forward to the extra work that will involve .

I also noticed I have an issue with my power source limiting maximum LED brightness. I used a PC ATX power supply rated in theory as 17A @ 12V, but, as load is added the voltage drops significantly. With the 8 lamps on 100% it drops to 10.5V... which means the current drops too and the LEDs aren't as bright as they should. I have already identified a good replacement (this one), intend to buy it this week. So, PAR measurements only after that is resolved. This is its power curve, notice it keeps voltage fairly steady as current/load increases:



Here is a tank shot, which I'm not very proud of posting, not because of the light (which I like and the picture doesn't reproduce faithfully), but because of the red bubble algae all around... yes, I let them grow too much... I was using all my reef time to finish this LED fixture and Arduino code. Now I'll attack the red bubble algae as I start to pay attention again to water changes, measure parameters, etc.


That’s it, I’m a happy member of the “DIY LED Club” now!!

Snorkeler