Rikko's DIY LED Moonlight (with lots of pics)

[Rikko]

After a few stunning photos from here and reef central, I decided that I absolutely needed one of these things, so I set about slapping one together.

Total cost:
50 ultra bright blue LEDs from BestHongKong's eBay shop: $8.50 incl shipping
3/4" PVC (had to buy a 10-footer, unfortunately): $3
----
Call it ten bucks, and that's because I bought far more supplies than I really needed.

Other parts:
40-Ohm resistor
5VDC adapter from my old Nokia cel phone
Glue gun and plenty of glue
Soldering iron and solder


Assembly was quite simply, actually. I cut my 3/4" PVC to 48" long (it's a 77 gallon tank) and then cut it lengthwise to get two half-pipes. I used an arborite knife to slowly cut it down. I'm sure a jigsaw or even a hacksaw would work if you weren't concerned about it being straight (though in hindsight, this jobbie isn't all that straight either).

Then I drilled holes in one of the sections of PVC to mount the LEDs. The spacing between the leads for each LED is 1/16" and the holes needed are 1/32". Needless to say I have no 1/32" bit nor am I compelled to make a perfect fit at 1am. I eyeballed the holes and gave myself two holes per LED to mount them.

I threw a glop of hot glue onto the "inside" of the tube between the holes and stuck the LEDs through. That compensated for the extra wide holes as it's practically moisture sealed now. Then I soldered everybody together in series... Realized I should have done it in parallel, and started all over again.

Finally did it right - 8 LEDs wired in parallel (ie. all the positive leads are connected to one another and all the negative/ground leads are connected to one another).



I believe the words you're looking for are "piss poor" - but after the first mishap I was fed up with soldering and just wanted it done.

Then I soldered the resistor onto the positive lead (ie. it's in between the LEDs and the power supply) and secured it with hot glue.


(Sorry it's fuzzy)

The positive lead I then soldered onto the other end of the resistor and the negative/ground lead went right to the LEDs.



Voila. It's 99% done. Now just had to clean it up. I used a generous dollop of hot glue for every soldered connection there, and one in the middle of every wire to keep them from moving. That also protects me in case it gets banged around a whole lot and the LED leads ever manage to short - they're not going anywhere.

Now I took the other piece of PVC and stuck it on top of the first to hide the wiring:


I used a but of glue to secure it down (not too much so I can get in there and service it if ever need be) - note that a couple of wires are poking out.. I should have paid more attention when I glued down all the leads.



The test!



Phew! A couple of dark shots just for fun:





Then I just dropped it on top of my hood. At the moment it's sitting over glass, but once I'm done fiddling with all my equipment, I'd prefer to have it right over water. It's just the small bit of PVC in front of my large PVC light fixture.



Flip it over, just to convince you:


I tried a few pics of the dark tank but I'm not adept enough at the manual settings on my digicam.



You get a very faint idea of what the bottom of the tank looks like under the moonlights:


And one shot with the flash so you get a comparison.



It looks absolutely gorgeous at night with your eyes, but it's really quite faint in my 77 gal and doesn't upset the fish from what I can see.
Just to give them a bit of a break from it, I have the LEDs clustered towards the left end of the tank. 6 of them are within the first 12" of tank, and the other two come to about halfway. The right end of the tank is pretty much left in darkness.

The cool thing about the LEDs is the tight beam - you can really play with it if you want a custom moonlight. I just drilled a couple of the holes towards the sides of the PVC to make them angle at the glass, but the effect could be much stronger if you focused a few on some choice plants or corals. I just did 8 total to see how it looks.. I'm happy.


A note about resistors for any who might want to do the same:
That 40 Ohm resistor wasn't arbitrary - it's calculated. I have 8 LEDs there, each of which wants about 15mA current. Since they are in parallel, voltage remains the same for each LED, but the current is additive (ie. you must have 120mA total current in the circuit, and not just 15mA). The power supply I was using provides 5 volts and 240mA (so more current than I need - the resistor is necessary). Ohm's law: R = V / I = 5V/120mA = 5/0.120 = 41.6 Ohms. 40 ohms is the closest I can get (The higher the resistor, the less current, the less light intensity. The opposite is also true, but you run the risk of premature burnout or totally frying the LEDs). So add the resistor before the positive input voltage hits the LEDs and you're fine.



Comments? Suggestions? Outright attacks on my character? :P

[corigan]

I think it's a pretty good job. I'm going to try to do one myself the same style. What was the mcd's of the LED's you bought?

Matt

[Rikko]

They were rated at 4000mcd. I got them from this guy. It's a pseudo-ebay store - I found it through his auctions. You might find better deals on them on ebay, but everybody else I saw either wouldn't ship to Canada or wanted too much for shipping.

His stats on the LEDs:

Luminous Intensity: 4000mcd@20mA TYP (LED is current driven, if used with 30mA, they're 6000mcd)

All LED should rated at 20mA only, if seller claims it's rated at 30mA or even 50mA, they actually overdrive the LED for higher mcd rating number. Try my LED with 50mA you will get about 10000mcd, however, it means the LED is more faster to DIE

Viewing Angles: 30 degree ( See it from the pictures! 30 degree's 4000mcd = 20 degree's 5000mcd!! )

His FAQ said 15mA - guess I could put a little more juice through them, but I rather like the dimness. I've since moved it behind my lights and my taller anubias look absolutely ghostly and I can see my rubber lip pleco storming around looking for something.

[corigan]

Thanks for the info. I was looking around at his store last night and assumed the 4000mcd were the ones you used. Thanks for the info, looks great.

Matt

[Fat Guy]

I like your DIY pvc light fixture. I've seen people make those out of rain gutters.

cool beans.

I dig moonlight too. I put 7 Leds on a wooden slat (like for blinds) hooked it up, wrapped it with electric tape and ta daa. It's got to be one of the best additions to the aquarium. I'm thinking about making some with white light.

Anyway, great addition.

[corigan]

What was the mcd of the LED's you used FatGuy?

Matt

[Rikko]

Finally a decent light shot:

[mjprather]

Blue looks nice. But moonlight is white. Just depends if you are going for aesthetics or realism.

Here is a 2 second exposure of one I made. The LED is about 2200 mcd with 110 degree viewing angle.