Making a moonlight effect

[Jen]

So I went to Radio Shack and picked up some stuff... 4 blue LEDs, some PC boards and some hook up wire (red black and green) So what do I do next? A friend of mine has a soldering iron, and im hoping some solder as well, and will hopefully do the job for me. I take it I need a plug to rip apart to wire it to.

How long, and labour intensive is the job?

 

[Discomafia]

Which Radio Shack did you go to? The one in Jackson Square?

 

[Jen]

No, Limeridge

 

[Lateral Line]

I made my comments in your duplicate thread here.

 

[smithrc]

as lateral siad in the other thread...

The LED's will need DC (not AC from the wall plug) a mains adapter will do that easily.

Dependiny on the LED's you got, they will have a MAX current spec (for most 5mm round LED's 20ma is a good figure) if that is the case...

3 will mean they need 60ma MAX current... so if you are using 12V from a DC supply you will need a 200ohm resistor (RES) across the LED's (O) (eg all the +'s together and all the -'s together with the resistor between them)

(if you are using a diffenent voltage the resistor will differ... Voltage divided by the current will give you the resistor... for 9V = 9/0.06 = 150ohm)

does that make sense?

 

[Jen]

wow. thats so greek to me. Lol. hopefully my friend will know what that means.

anyway, my LED package says they are 5mm, 10mA each. I have 4 of them, and 4 mini pc boards. ill have to string them all together somehow.

Will i have to waterproof it at all?

 

[smithrc]

i'd protect the connections and that about it
(check for rust and if it happens - waterproof that bit too)

If they are 10ma and you have 3 of them they might not be bright enough...
do you have a part number i can look up?

 

[Jen]

Heres the link to it

LED's at radioshack

 

[Lateral Line]

SmithRC:

I would have wired the LEDs differently. I'd have used a resistor on each LED...

Vcc ----------------
        |   |   |   |
        R   R   R   R
        |   |   |   |
        D   D   D   D
        |   |   |   |
0V------------------

The rationale being that if a LED fails, and you have used a single resistor assuming the shared load, the remaining LEDs are now able to draw too much current and are likely to fail early.

I cannot calculate the values of the resistors since it does not say what the forward voltage of the LEDs is - most blue LEDs I have seen have a Forward Voltage in excess of 3V.

 

[ChriX]

I agree with LL here. If they were wired as per the first diagram, each LED would have 12v across it, which would result in dead LEDs!

 

[smithrc]

SmithRC:

I would have wired the LEDs differently. I'd have used a resistor on each LED...

Vcc ----------------
        |   |   |   |
        R   R   R   R
        |   |   |   |
        D   D   D   D
        |   |   |   |
0V------------------

The rationale being that if a LED fails, and you have used a single resistor assuming the shared load, the remaining LEDs are now able to draw too much current and are likely to fail early.

I cannot calculate the values of the resistors since it does not say what the forward voltage of the LEDs is - most blue LEDs I have seen have a Forward Voltage in excess of 3V.

good point - well presented

Normall I actually calculate the resistor so that if one fails the rest get their max current so none will be over driven - and only needs 1 resistor.

there is not enough data on that page to tell you anything useful i'm affraid...

as LL said most blue LED's have a Forward Voltage in excess of 3V sometimes up to 4.5V...

 

[mrV]

Here is a picture, in which way I made it. I used super-bright leds.

Here are also some pictures about simple moonlight system.

It's important to use resistances with leds or they will burn. If you don't know how much those leds takes, you can use some values for them: 3,5V and 20 mA. (Although, those values are for super-bright leds (7-9 candela), not for basic, dimmy ones..) You should check how many voltage your transformer gives when the system has been build. If transformer is "unregulated", then it probably "overfeeds" and you need to use those values when calculating resistance. With "regulated" transformer is much easier - transformer gives always exactly voltage.

 

[Max]

this is a somehwat old post but i would like to say you also need 470-480 nm (nm? i just know you have to) i am allso building one into my hood on my next tank. look on ebay putin the search 'blue leds 470' and search in description and title.

 

[mrV]

470-480 nm

Why? In freshwater real "moonshine" isn't needed like e.g. in reef tank. But I don't know which nm is right for corals - i have no sw tanks

And be careful with the tranformer. LEDs burn easily!

 

[Jen]

Sheesh. I posted this ages ago, and I still havent done anything with the stuff I have. Thanks for all the replies, I will take all this in consideration - if I ever get to build this. I may just go the easy route and get one of those blue strip light thingies that you can buy for your car. 30 bucks, but easier than souldering it all together.