DIY LED Fixture for 7 Gal (w/ pics)

[Hoppy]

I have been thinking about how much a LED light for a 10 gallon tank would cost. So, I think I will make that a project for today - not making one, but trying to design a minimalist one. I do have an empty 10 gallon tank, but, please, please, I hope this doesn't get me back to two operating tanks again!

EDIT: It looks like I could make a 10 gallon LED fixture, giving moderate lighting intensity, using 16 Cree LEDs, for about $125 total, making good use of surplus materials. Not cheap for a 10 gallon tank, but the need for DC power, a heat sink, cooling fans, etc. makes it almost impossible to build one cheaper than $100, no matter how ingenious you are. You have to look at this as half entertainment and education, and half getting a nice light fixture.

[Temuchin]

As Hoppy says, this type of project is not about saving money. Its more of a "craft" project. This is what happens when you get rid of your TV.
I also had a need for a custom solution to upgrade my lighting for a non-standard fixture length.

[purplecity]

ok let me see if i have the right idea, in my diy light fixture i would use a very thin plate of aluminum, attach the leds, the dc power, and fans

so my parts list would consist of
- 22" aluminum plate
- 16 Leds
- one computer fan
- dc power supply

what other parts would i possibly need? the led driver or something?

i really really love this led fixture made byKev82!



i know i can get my hands on a aluminum plate from homedepot or some place cant be that expensive , i think i may have a dc powersupply if i look through my stuff, a pc cooling fan is easy to get

so all these items stated above will be cheap the main important and expensive stuff would be the led's itself

what if all the people intrested in making Led fixture got together and we order over 150 LEds im sure we could get it for cheap,

Also there is a led store on ebay can anybody check to see for the cheapest led bulbs we can use that would output enough light for 10 gal?


i think if we all work together we can find the best cheapest and most effective way to create led fixtures

[Hoppy]

Actually the LEDs are not even half of the cost! http://www.dealextreme.com/details.dx/sku.2395 is the cheapest source I have found for high power LEDs suitable for our use. Note that this particular batch is a "bin" of lower lumen output high power Cree LEDs.

Just a flat aluminum plate might work ok, but keeping the LEDs cool is a major requirement for long life and most output, and they do get very hot if not actively cooled. A finned aluminum heat sink extrusion is obviously the best idea, but my local surplus metals dealer sells aluminum extrusions, not heat sink extrusions, that include all sizes of channels. They are sold in 8 foot lengths. So, for a 20 inch long heat sink, that gives you 5 lengths. A 10 gallon tank is about 10 inches in depth, so 2 inch channel would give you an almost perfect fit with the top. But, you don't need that, so a 1.5 inch channel gives you a 7.5 inch wide heatsink, which is perfect. And, 1.5 inch channel is only about $15 per length - very cheap. But, you have to use a heat conducting grease between the channels, and rivet or screw them together, side by side. So, $15 plus about $5-$10 worth of grease, and another $5 worth of nuts and bolts will give you a heat sink.

The DC power supply has to provide enough amperes to drive all of the LEDs, and at a voltage that lets you put the LEDs all in series, or in parallel groups of equal numbers of LEDs in series. Each LED will use about 3.1 to 3.6 volts. If 16 are put in series, the DC voltage required is 16 x 3.6 volts, or 57.6 volts, but you need a bit more in order to limit the current, so a 60 volt source is needed. The LEDs, for maximum output, will need .7 amps, so that 60 volt supply has to be capable of 700 mAmps output, preferably up to 1000 mAmps (1 amp). It is hard to find such a AC to DC converter with those parameters.

To control the current you need 1% resistors, maybe at worst 5% resistors, able to handle the power you will drop on the resistors.

For best cooling you need two fans, 12 VDC and a power supply for them, or 110VAC, which are more expensive.

To mount the LEDs you need a heat transmitting grease or adhesive between each LED and the heat sink, and that stuff can cost from $3 to $20.

Even hookup wire isn't free, and nuts and bolts, switches, etc. all add up too. And, you still don't have a nice looking housing for the light fixture.

The important thing is to really enjoy the adventure of learning about LEDs, electric circuits, designing the fixture, and making it.

[kev82]

Well there is one factor that might save you a little cash in the long run. You don't have to replace the LEDs anywhere close as often as fluorescent bulbs. F.e. the cree LEDs I used for my build are rated that after 50,000 hours of usage they will emit 80% of the light they originally emitted.

I did this mainly for the fun and learning factor tho. Doing stuff like this yourself is fun stuff

[Hoppy]

You also save some electricity. It appears that a LED light can be about half the wattage as a PC light for the same light intensity. That also gives you "green points" with the green crowd. And, I'm sure there will eventually be easy to use devices available to power the LEDs without spending so much.

Also, I visited my surplus metals store and found that aluminum plate is $3 per pound, pretty cheap, and they had some aluminum channel, at $15 per 8 feet like:


This channel is perfect for a row of LEDs. It is thick enough to be a very good heat exchanger, and just the right size to mount LED "stars" on it, with fan cooling behind.
For an 18 inch long piece that would only be about $3 for each row of LEDs. If there were enough interest I would be willing to buy an 8 foot piece and sell it at cost, plus shipping. Heat sink extrusions start at about $20 per foot.

I apologize for hijacking the thread, but at least this is on topic to some extent.