HELP! DIY moonlights not working!

[JProx]

lol well radioshaft wants 4bucks an led, lsdiodes is like 400times cheaper than radioshack, you will get you're leds from them next week, mid week i will bet. they are pretty fast shippers. i know your joking (at least i hope you are) but that entire sub fixture with a reflector is totally not neccessary. leds push close to 80% of the light through their tip, which means only a small % is actually escaping from the backside, so going through the pain of installing a reflector to gain 10% extra light (led's are not 100% effecient, they are pretty close though) is pretty much a waste

what i did for my 12gal eclipse tank, was grab some scrap 3/4(width) plywood, cut to fit (and boy was that a P.I.T.A) polyurthaned it, then drilled 5 holes, counter sinked them so the leds would fit inside the wood, the soldered wires to the legs, filled the top section of the countersink with aquarium sealent (to prevent water from entering there) ran the wire through the holes, installed the resistors on the top of the wood, soldered all the wires together, then ran them out of the tank, and to the dc adapter. it's really simple and i will take some pics if you want.

i was just doing some math, and i believe your 130ohm resistor choice is bit off.
9v source - 4v required voltage = 5v / 20mA = 250ohms, so you should pick something between 250 - 300 ohms, to be on the safer side.

 

[dralarms]

I looked at those led's and they seem to be the same ones I ordered from lebos.com. Thanks

 

[Gauge]

I have a question on this. Tripoli was saying (on the phone with me anyway) that his circuit didn't work unless he had the resistor on the positive side. Should that matter? I didn't think it would matter one way or the other since it would still change the wattage going through the LED.

 

[JProx]

it will work with the resistors on either side of the led, they *should* be on the negitive side, but will generate the same results if they are on the positive (or annode) of the led. as a matter of fact i have another led project in my prototype board (rigged up to a few different ic's) that have the resistors on the positive leg of the led.

the resistors don't change the wattage, what they do change is the voltage and current running through the led. wattage is a product of voltage and current (p= v x i) and it's used to measure how effecient a circuit is (Pin / Pout = Eff /100 = xx %) and how much heat it's generating.

 

[dralarms]

what they do change is the voltage and current running through the led

But actually current runs from negitive to positive so you are correct in stating it should be on the "negitive side".

 

[JProx]

well..
you're right, current does run from the negitive / netural portion to the positive side of a power supply. however an ideal power supply generates very little (or theoritcally zero) amps and the circuit is responsible for generating the current it needs.

added info: a battery though, does generate a little bit of current, since there is a very small resistance value inside the battery, which is why a battery loses it's charge after a while.

in a simple current limiting / voltage divider circuit having a resistor on the positive or negitive side of an led, will generate the exact same results. it should be wired so the resistor is on the negitive led, but really it doesn't matter in this application.

 

[Gauge]

Okay, I have a new question. Tripoli was saying that he put two of the LEDs in series as a test. He was using a 9VDC power supply and the LEDs are 4.5V (typical, not max). Shouldn't that work without a resistor? He said that it blew both the LEDs. I tried it at home, and got the same result - they lit for about half an hour and then blew.

 

[dralarms]

A new 9v battery has actually 9.8 v to begin with. I know that with resistors if you series them you cut the resistance in half but I don't think it's the same for voltage. In other words you still had 9 vdc going through the led.

The way to check this is place your power supply on the led, and measure voltage with them in series. I think you will find that voltage remains the same and current is what changes.

 

[JProx]

2cents you're a little confused on the subject..

in series voltage changes (each voltage drop is added together) and current stays the same. in parallel voltage stays the same and current changes. if 2 blue led's are in series with 9volt source, they will blow, why? because blue led's operate in a range of voltage, from 3.8 to 4.2volts. 9volts / 2 = 4.5volts, about 300mV over their max value. the greater the difference over their max value the faster they will blow.

resistors in series add up (R1 + R2 + R3 ect = Re ) in parallel they divide
[(1/r1) +(1/r2) + (1/r3) = 1/Re] Re = equivalent resistance. a little reminder i always thought was helpful, if 2 resistors in parallel are the same value divide the value by 2, and if they are all different the result of the formula will be less than the lowest resistor you have.
an example:
r1 = 1k
r2= 2.5k
r3=5k
1/1k + 1/2.5k + 1/5k = .0016
1/.0016 = 625ohms

so i still feel the best way to build a moonlight is wire the led's in parallel, so you don't need more voltage (in parallel volage is dead locked, it's the same for all components in the paralleled branch) in series you will need to have ~4volts for every led you have in the circuit (5leds x 4v = 20volts). so parallel is the best possible way to build this circuit, it's just so much more efficient. and i have been thinking about doing this for a while.. but perhaps i should just write up a post on how to build moonlights, and the theroy behind electronics... didn't think there was enough of a need though before.

hope that helps.
bry

 

[dralarms]

Got my series and parallel mixed up again. I'm always doing that. yea that's right.

I got a "moonlight" instruction book if you want it. pm me with your email addy. (no hotmails & yahoo) the file is 2.5 meg.

 

[JProx]

well i am electronics major, so i am pretty good on the electronics issue, however i am always looking for better ways to mount / install these new fangled moonlights. does that book have anything on mounting issues?
2cents if you want any help, ever with anything electronical.. by all means email me, i am always glad to help. ijedi@hotmail.com
I'm here for you and the rest of the squad at aquarium advice.com! lol

 

[dralarms]

I appreciate that. However I deal with electronics every day, I just get the series and parrell mixed up sometimes. I deal with alarm systems so I know which one does what I just get it backwards when I try and explain it. . It's really nice of you to offer your help to all of us at AA

 

[Tripoli]

Well, just though I'd let y'all know that I've finally got them up and running. lsdiodes.com was a wonderful site, BTW. I'll be sure to use them in the future.

The lights look great. Until I get a canppy built for my tank, I've just got the LEDs taped facing into my main lights' reflectors. To help dispurse the light a little more, I'm temporarily using plain old Scotch tape placed over the LEDs. Once it gets dark outside I'll probably take a pic so y'all can see how it came out. 8)

 

[JProx]

lol great, i would like to see the final results of all my hard work.. hahah. lsdiodes.com is a great store, hard to believe it's a basement company (a company ran out of some one's basement) fast shipers, and super cheap led's, but quality led's, i can't wait till they get some 20k+ mcd ones in. anyways i am glad i could help and if you ever want to add some bells and whistles to the moonlight, just let me know.

 

[Tripoli]

What kind of bells and whistles CAN you add to moonlight? :?

 

[JProx]

a timer or a photo sensitive system, dimming capabilites mostly. i knew i shouldn't have said anything.. sigh (joke)

timer uses a simple 555timer (ic) and a few common components, a resistor and capacitor, to make a timing constant. good for timing jobs in the micro second to the days.

-= or =-

photo sensitive system (my favorite)
instead of a timer, you install a special purpose diode that is sensitive to light, and wire it so when lite is not detected to 'turn on' the moonlight. basicly it's a fancy switch. here's the system in bit better detail.. install the photo sensitive diode near the existing lighting fixture, when that gets turned off the photo diode detects no light and turns on the moonlight and when the main lights come back on, the photo diode detects the light and shuts off the moonlight.

and/or you can install a dimmer switch to fine tune the moonlight's output. like i suggested before finding an external medium is the best choice.. but it's very simple to do, however it's not a 'true' dimmer, but it works in that capacity. all you will need is a 50k wand potentiometer (or pot for short) which is nothing more than a variable resistor, it can change it's outpot from ~0 to ~50k Ohm, also remember that 5% tolerance thing i was talking about ealier, it's valid on pots too. radioshack sells them for 1-2 bucks i believe, you install that between the dc transformer and the leds. i made up a pic for another aa member on how to install it. oh yeah bow down to my uber MSpaint skillz. lol http://12598.tripod.com/Pot.jpg
you will want connect terminal's A and C. if you connect anything else you will not have a variable output, it will be deadlocked at max resistance value of the pot, which happens to be 50k in this example.
if you hook up A and B = deadlock, B and C = deadlock

easiest addition is the dimmer pot, it's not a true dimmer, and i will save you from the theory of why it's not but it still works reasonably well as a dimmer. the timer is medium in the difficulty department, it's not that complex to build or do the math for, but can prove to be a pain if you exceed their max voltage/current requirements. and the photo diode idea isn't that hard it's just finding good ones, that's the problem. the ones radio shack sells have poor reactions (from personal experience) where it can take a full 75w bulb put 6inches from the diode to get it to react to the light and they weren't cost effective enough to buy from digikey.com either. (cost effective opinion is based on experiecnes from 2yrs ago, so plz don't quote me on that)

there are other things to you can do with led's but they don't really fit into the aquarium too well. those are the 3best ones i can come up, if you have any ideas on additions i am all ears.

 

[Tripoli]

Definitely some neat tricks. Nothing I think I'd like to incorporate into my tank, but neat nonetheless.

 

[Micro Reefer]

Very interesting thread. I've been searching for ways to upgrade my current lighting system with Red LED's for nighttime viewing of nocturnal creatures. I'm using a Custom Sea Life PC fixture with build it Moonlight. The only way to turn the Moonlight LED on is to plug in the transformer or put it on a timer. I decided to put a switch in the hood so I can easily turn it on and off. But since I'm gonna be drilling holes and cutting wires while having my light fixture disassembled, I'm also going to install the Red LED's. I just places an order with www.superbrightleds.com
They seem to have a large selection and pretty good prices. I'll let you know how the service turns out.

I'll post pics with the progress

Again, Awsome Thread!!

 

[JProx]

i have seen that site before, but i was turned off by the layout (looked like a 3yr old desgined it) and looked for another led supplier. let me know how your transaction turns out micro ?

i am putting together a walkthrough / faq on moonlights, and electrical theory, so if you have any questions look for the thread, or just email.. i will be more than happy to help.

 

[Micro Reefer]

I just recieved my order from superbrightleds.com and everything went smooth. I wasn't sure wich ones to get, so I chose a variety since they were only about 60 cents a peice. The ones I chose were:

1500 mcd / 60 degrees ( light spread angle )
8000 mcd / 30
12000 mcd / 8

I'm now searching for a nice switch for the hood. Form is just as important as function for this part.

Jprox,

any input is well appreciated. I started my search for light switches at Kack Shack because it was very close to the house.

MR