Running Moonlights? Please Read this.

[smcnally]

Just wondering how many people are using the exact setup in this DIY setup, and have been running them for a fair amount of time? http://www.kaotica.com/frag/diy/moonlight/ . I wired mine from a different method I read about and all 20 of my LEDs burned out after about 4 nights of use. My boss said they would last longer if I ran 6 in series with a 100 Ohm resister at the positive side and powered it with 24VDC. That way each resistor would get the same exact load, and they would all get the reccommended voltage/amperage. Man, I used to really know this stuff, but I've been braindead lately, and just can't do the calculations without screwing them up.

 

[mattn007]

Most likely you were running way too much current through your LED for it to burn out in 4 days. I am not using the exact setup but I may be able to clarify this:

Lets define the following:

V(led) : The "ON" voltage drop across the LED. Obtained from a datasheet, varies greatly by color and a little bit between different models of the same color.

I(led) : The recomended current through the LED from the datasheet. Usually 0.02A

Vcc : The supply voltage. This is the DC voltage from the transformer.

R(set) : The value of the resistor used to control I(led). This is the 100 ohm resistor your boss properly suggested.

N : The Number of LEDs in serial.

The equation for the circuit is:
Vcc = N * V(led) + I(led) * R(set)

-OR- solved for R(set)

R(set) = (Vcc - (N * Vled)) / Iled

Decide what supply (Vcc) you want to use and what LED and then choose N and R(set) accordingly.

A typical 5mm wide Blue LED has the following specs:
V(led) = 3.5V
I(led) = 0.02A

With a 5V transformer we could only have one LED in series (for multiple LEDs put them in parallel). R(set) = (Vcc - (N * Vled)) / Iled = (5 - 3.5) / 0.02 = 1.5 / 0.02 = 75 ohms

With a 24V transformer we could have six LEDs in series.
R(set) = (Vcc - (N*Vled)) / Iled = (24 - (6 * 3.5)) / 0.02 = 3/0.02 = 150 ohms

If we only used one LED with the 24V transformer we would have
R(set) = (Vcc - (N*Vled)) / Iled = (24 - 3.5) / 0.02 = 1025 ohms

Also make sure the LED is wired correctly. The longer wire on the LED should be connected to the positive voltage (closer to the transformer + output).

Here is a crude drawing of the circuit:
Vcc ___
|
/
R(set) \
/
|
_|_
LED _V_ Possibly several LED in series here.
|
|
|
__|__
GND -----
--



Hopefully this helps.
-Matt

 

[gordonzoo]

Ohms law E = I/R E x I = Watts
Two things you need to worry about. Just make sure you do not put more than 3.5 volts across each junction. I keep mine closer to 3.v per junction. The more LED in series the less voltage drop across each LED.
And what some people forget is to make sure you don't overdrive the resistor's wattage They also burn up. The smaller resistors could be anywhere from 1/8 watt to 1/2 watt and by encapsulating this rating could be lower.
I think your boss is pretty close. I would personally add one more LED in series though so not to over drive. However, nothing beats a meter. Just make sure total series circuit it is under .020 amps (20.ma) and resistor is rated for wattage.
Rich

 

[gordonzoo]

Remember, if you use 1 led on a 24.v supply @ .02A the wattage of the resistor needs to be 1/2 watt or greater to dissipate that heat.
24 v x .020 A = .48 watt
This is why it's better to series the LED's in a higher voltage circuit. The voltages will drop across each LED to reduce Voltage load on the resistor and lowering the wattage requirement and ultimately making the circuit more efficient.
Rich

 

[mattn007]

I agree with Rich, the 1 resistor 24 watt was more a mathematical example. In reality you should either use more LEDs in series or a smaller power supply.

If you keep the voltage across the resistor to 5V or less you should be ok to use all the resistors you might find. 5 * 0.02 = 0.1 watt To do this make sure Vcc - N * Vled < 5V

 

[sanker]

Everyone needs this in their tank!!!

i followed the directions at the above site. I bought the same leds fabio used (his link is dead ,the leds were: 500TB4D, Blue LED - Super Bright(30 Deg.) 15 for $21) , used an old 9v, 700ma radio transformer. had my buddy (also happens to be my boss and has a PhD in Physics and does lots of work with electronics), who didn't blow as many brain cells as i did in high school, do the calculation for the resister. I told him the specs on the above listed power brick and LEDs and he came up with this resister: power 0.4 W, resistance in Ohms 301. digikey part number:
BC301YCT-ND
digikey.com


i wired them up in parallel
I used 5 LEDs.

you can see pics of the tank here:

http://homepage.mac.com/sanker/PhotoAlbum36.html

the LEDs should not be hot. if you use teflon coated wire (I used 20awg) it's much stiffer and you can actually bend the wire into highlight position. it's pretty dramatic.

LEDs
http://www.lc-led.com/Products/department/1

I bought:
500TB4D
Blue LED - Super Bright (30 Deg.): 4,500 mcd
T1 3/4 water clear 5mm super blue. Color: InGaN blue (470 nm). Intensity: 4.5 cd (typical). Viewing angles: 30 Deg. Solder leads without stand-off. For optimal colorization and intensity (4.5 cd), forward voltage of 3.3V is recommended.

they are 30deg viewing angle

this other one:
500TB4DF
Super Blue Led Lamp (60 Deg.): 2,600 mcd
T1 3/4 water clear package. Color: blue (470 nm). Intensity: 2.6 cd (typical). Viewing angles: 60 Deg. Solder leads without stand-off. For optimal colorization and intensity (2.6 cd), forward voltage of 3.3V is recommended.

is 60deg but 2.6cd (candle?) vs. 4.5cd for the ones I got. Mine are a bit to much like spotlights but once I upgrade to my new 90gallon they should be fine. makes sense that the candle power should be half if you are spreading the light over double the area (60vs30deg)

mine are on day 3 now. they go on at 7pm and off at 7am. I think I may need to cut down the time...turn 'em off at 4am
hope this helps.

Smcnally, your xenia looks great in my tank (see links off of the above website for Sanker Marine Aquarium) and the flame torch rocks in my 180 at my office...
your activeX app doesn't work on my mac, could you send some pics of the anemones?

-Sean

 

[smcnally]

I'll take some pics of them today. They are both doing great. Both of my clowns are hosting together in them, and they tade off witch one they want almost daily. Good to hear the Xenia and Torch are doing well.

Everyone needs this in their tank!!!

i followed the directions at the above site. I bought the same leds fabio used (his link is dead ,the leds were: 500TB4D, Blue LED - Super Bright(30 Deg.) 15 for $21) , used an old 9v, 700ma radio transformer. had my buddy (also happens to be my boss and has a PhD in Physics and does lots of work with electronics), who didn't blow as many brain cells as i did in high school, do the calculation for the resister. I told him the specs on the above listed power brick and LEDs and he came up with this resister: power 0.4 W, resistance in Ohms 301. digikey part number:
BC301YCT-ND
digikey.com


i wired them up in parallel
I used 5 LEDs.

you can see pics of the tank here:

http://homepage.mac.com/sanker/PhotoAlbum36.html

the LEDs should not be hot. if you use teflon coated wire (I used 20awg) it's much stiffer and you can actually bend the wire into highlight position. it's pretty dramatic.

LEDs
http://www.lc-led.com/Products/department/1

I bought:
500TB4D
Blue LED - Super Bright (30 Deg.): 4,500 mcd
T1 3/4 water clear 5mm super blue. Color: InGaN blue (470 nm). Intensity: 4.5 cd (typical). Viewing angles: 30 Deg. Solder leads without stand-off. For optimal colorization and intensity (4.5 cd), forward voltage of 3.3V is recommended.

they are 30deg viewing angle

this other one:
500TB4DF
Super Blue Led Lamp (60 Deg.): 2,600 mcd
T1 3/4 water clear package. Color: blue (470 nm). Intensity: 2.6 cd (typical). Viewing angles: 60 Deg. Solder leads without stand-off. For optimal colorization and intensity (2.6 cd), forward voltage of 3.3V is recommended.

is 60deg but 2.6cd (candle?) vs. 4.5cd for the ones I got. Mine are a bit to much like spotlights but once I upgrade to my new 90gallon they should be fine. makes sense that the candle power should be half if you are spreading the light over double the area (60vs30deg)

mine are on day 3 now. they go on at 7pm and off at 7am. I think I may need to cut down the time...turn 'em off at 4am
hope this helps.

Smcnally, your xenia looks great in my tank (see links off of the above website for Sanker Marine Aquarium) and the flame torch rocks in my 180 at my office...
your activeX app doesn't work on my mac, could you send some pics of the anemones?

-Sean

 

[heavydc2]

I did the moonlights of the link above and I also wrote a quick article for an old version of currents. Here is the article http://www.chandev.com/reef/Led-Moonlighting-Project.pdf its spelled out very simply.

I think one of the things that is missed with the whole moonlight thing is that it should be very faint light if you look at the intesity of the lights in Sankers pictures it looks very intense, the picture could be decieving. on my setup I have the voltage up to 3V, and anything higher looks too bright. Just food for thought.

 

[sanker]

-=-=-=-==-

I think one of the things that is missed with the whole moonlight thing is that it should be very faint light if you look at the intesity of the lights in Sankers pictures it looks very intense, the picture could be decieving. on my setup I have the voltage up to 3V, and anything higher looks too bright. Just food for thought.
=-=-=-=-=-=

I meant to mention that. I used my camera on a tripod with a very low shutter speed. The pics are WAY brighter than what you actually see. I couldn't get my sony 4m pixel (s85) to find a happy medium between too bright and too dark, like the one in your pdf . you can see the motion blur on the anemones and frog spawn from the slow shutter. nice pdf.