Hey everyone. I want to start this by saying two things.
1- Yes...I'm new. And when it comes to case modding...I'm only about 1 or 2 steps above a total N00B! (I added a window to my case...LED fan...and neon tube(which was removed...the LEDS look better by themselves.)
2- I know very little about this kind of stuff. I have a basic understanding of electronics, and I learn quickly, but right now my knowledge is certainly lacking...

Here's the problem. I am trying to build an LED system that is really easy to put together for someone who doesn't know anything about anything. This system needs to be something you could plug into a wall socket and it lights up. Unplug it and off it goes. No need for switches or anything like that. Should run anywhere from 4 to 6 blue LEDs. These will be used to highlight aquariums after the normal lights are out. (It apparently simulates moonlight, and this seems to be good for fish.) I'm planning on making a guide for some people to re-create this for their own use...but I can't get it to work myself!

Here's what I'm up to so far. Feel free to make fun of my general lack of knowledge (see #2 above) before being helpful.

When I decided to start this project, I went hunting for a spare AC adaptor. I have lots...the first one I saw gives me an output of 12V DC at 800 mA. Cut the plug off, separated and stripped my wires. ID'ed the positive side (multimeter says it's actual output is closer to 16v DC.). I bought some LED's to experiment with at a local surplus shop. I bought 10 LEDs that looked blue in the store, but now appear to be closer to a light purple. As these are all surplus, I don't know exact specs for them, but I'm assuming about 3.5v, need about 20 mA. I connected 4 lights in series (negative side to wire to positive side of next LED...etc). Now here's where I think I have issues. From what I have read in the last few days, it would seem that I should be able to get these to light...even if at a level brighter than normal and shortened lifespan...right? How should my adaptor be connected? If I connect positive to the first positive side on my LED, and connect negative to the neg. of the last light in the series, I get nothing. Power reads 15.9V on positive side, 0 on the neg. side of the same light, and obviously nothing beyond that. I get the exact same result reversing the wires (just in case I somehow confused the two...?) I get this result no matter where I try placing the two power wires.

What is it that I'm doing wrong that won't make this work? Also, shouldn't I be able to "test" an LED using a 1.5V battery...say like what sits on a mobo? I tried this with about 5 of the LEDs, and none lit. Is it likely that I bought at least 8 bad LEDs at the same time? I did only pay like $0.15 each....

thanks for any help you may be able to give me

LED is a light emitting diode .a diode is simply put,a gate that only alows electrons to flow in one direction.So you cant go in series.Each light will have to be wired in paralell.you'll need a resistor to lower the voltage ,dont know what size.Im sure its in the forum if you search.or some one will post it .and welcome to PimpRig.

hmmm....I understand how they work...but why shouldn't current flow from the positive side of one, through and out the neg. side, and then back into the next positive side? How would that be different from wiring them in parallel (excluding the obvious diference in voltage)?

When you are doing case mods and using a molex connector you are wiring two LEDs in series...right? What changes?

Now, You must use a resistor for the LEDs or else they will go poof. You can hook 3 LEDs up in series with 1 single resistor. If you want more though you have to have 1 Resistor per LED. I use 200 ohms to 270ohms(but 100 ohms + is fine)

Now, look at the top of the LED. You will see one flat end. This is the cathode or negative side of the LED that goes to ground. OR look at the led, and one lead will be shorter. This is still the cathode. The other is the anode which goes towards the positive end of the power supply. The resistor can go on any lead. It doesnt matter.

LEDs in series-Imigine 3 LEDs and one resistor. Vcc=12V. Each LED will take up 3 volts each. 3X3=9. (v, so the rest is taken up my the resistor. The resistor limits current in the circuit. Although it is a series circuit and current is common, it still limits it to a safe level for the LEDs.

Leds in parallel-In parallel, the leds get the same voltage (12V) no matter what. The purpose of the resistor is to limit current to the single LED.

Imagine a small circuit if you will, 3 Leds in series, Vcc=12. One side of the LED will be more positive (or negative if you have it hooked up right.) This difference will cause current flow. When the leds arent biased, they get full voltage but no current (an open)

Quote: Originally Posted by Nerdz Now, You must use a resistor for the LEDs or else they will go poof. You can hook 3 LEDs up in series with 1 single resistor. If you want more though you have to have 1 Resistor per LED. I use 200 ohms to 270ohms(but 100 ohms + is fine) Now, look at the top of the LED. You will see one flat end. This is the cathode or negative side of the LED that goes to ground. OR look at the led, and one lead will be shorter. This is still the cathode. The other is the anode which goes towards the positive end of the power supply. The resistor can go on any lead. It doesnt matter. LEDs in series-Imigine 3 LEDs and one resistor. Vcc=12V. Each LED will take up 3 volts each. 3X3=9. (v, so the rest is taken up my the resistor. The resistor limits current in the circuit. Although it is a series circuit and current is common, it still limits it to a safe level for the LEDs. Leds in parallel-In parallel, the leds get the same voltage (12V) no matter what. The purpose of the resistor is to limit current to the single LED. Imagine a small circuit if you will, 3 Leds in series, Vcc=12. One side of the LED will be more positive (or negative if you have it hooked up right.) This difference will cause current flow. When the leds arent biased, they get full voltage but no current (an open)

To quote myself in an old thread:

Quote: Originally Posted by putwig I can tell you how to do it, but I learned from this guy: http://www.dansdata.com/caselight.htm So, I will just let him teach you too!

I didnt quote that site..lol I never knew it exsisted (I dont really understand what your trying to say)...I wrote that from my own knowledge.

hmm thats a good Idea though, using a clear box with a bunch of leds in it..

Ok, let me make sure that I'm understanding this correctly. Basically mine doesn't work because I don't have a resistor in use? I just thought that even if it were overdriven, it should still light for a second...even if it did die immediatly after....I haven't seen light comming from these things once!

Let me try this. The negative side of my AC adaptor...should that be running to the neg. side of the LED string...or do I need a seperate ground for the LEDs and cap the neg side of the adaptor? I've applied basically everything you all have told me so far (Johnny English has a wonderfull LED primer on this site somewhere that I read before asking this question), but I'm still stuck.

Thanks for everything so far!

Quote: Originally Posted by Nerdz I didnt quote that site..lol I never knew it exsisted (I dont really understand what your trying to say)...I wrote that from my own knowledge. hmm thats a good Idea though, using a clear box with a bunch of leds in it..

I was just giving a good link to the original poster. It was not directed to you.

The "Quote Message in Reply" box just happened to get ticked. Sorry for the confusion.

Put

Quote: Originally Posted by ismisunderstood Ok, let me make sure that I'm understanding this correctly. Basically mine doesn't work because I don't have a resistor in use? I just thought that even if it were overdriven, it should still light for a second...even if it did die immediatly after....I haven't seen light comming from these things once! Let me try this. The negative side of my AC adaptor...should that be running to the neg. side of the LED string...or do I need a seperate ground for the LEDs and cap the neg side of the adaptor? I've applied basically everything you all have told me so far (Johnny English has a wonderfull LED primer on this site somewhere that I read before asking this question), but I'm still stuck. Thanks for everything so far!

Note, The 16V you are getting is 16V PEAK. Why? Time for a little lesson in electronics (sorry I didnt see this before..) The transformer inside is most likely a 12V RMS transformer, which would give 16.67V out. If there is 1 diode for regulation it would give 16v (because the diode drops .7V)After filteration (caps) you get your 16v (the signal is much cleaner than before and allows for more loading ti happen)

Now on to your question. Please..tell me you used resistors on those LEDs...or else you may have wasted some. But dont panic just yet. Go buy some resistors around 100Ohm to 270ohm (I use 270ohm )Connect one of the leds at at time to the resistor connected to power. You know your + side (also called VCC sorry..), and negative side (aka ground), if they light then they are good. Chances are you could have connected them wrong or gave them too much current to handle

Check out the link Putwig gave ya, will help out alot too.

EDIT:

Quote: Originally Posted by putwig I was just giving a good link to the original poster. It was not directed to you. The "Quote Message in Reply" box just happened to get ticked. Sorry for the confusion. Put

Its ok.Dont worry about it.

Quote: Originally Posted by Nerdz Now on to your question. Please..tell me you used resistors on those LEDs...or else you may have wasted some. But dont panic just yet. Go buy some resistors around 100Ohm to 270ohm (I use 270ohm )Connect one of the leds at at time to the resistor connected to power. You know your + side (also called VCC sorry..), and negative side (aka ground), if they light then they are good. Chances are you could have connected them wrong or gave them too much current to handle

I did not use resistors. Don't worry, I'm only out about $0.90. Actually, I discovered the multimeter I have allows me to check diodes (how convenient...) The four that I didn't kill are reading anywhere from 1.09V to 1.15V forward voltage...guess it's safe to say they aren't blue! The other 8 are all reading over-range...which is how my meter shows an open. Oh well...not like I'm out bunches of money! (hey...that's why I bought cheap LEDs in the first place!) I'll figure out the correct resistor ratings from the links above and get one (I'll go ahead and get the correct one for the real blue ones too), hopefully tomorrow. I'll post back and let you all know how it works out!

Really appreciate all the help. This is the only site I've found that seems to have people who actually know what they are talking about!

PR is a place where many different people meet, of many different skills. Most of us are JUST computer modding, theres more to this place than it seems. Stick around and you'll find out about the PR sock and many other weird things...

Quote: Originally Posted by Nerdz Stick around and you'll find out about the PR sock and many other weird things...

The what...?

Quote: Originally Posted by ismisunderstood The what...?

Exactly .

Wow reminds me of physics class last year. All the wiring and voltage and current and resistance. Ask your physics teacher about that kind of stuff he should know a little. I already forgot a lot about it.

i know this may be a lil off but other then being a computer freak i have lots of pet fish i made one of this for my 30 gal with 6 leds put it right into the hood i also made one for my girl friends 10 gal i used a 12v power supply i made till i found a old cell charger so its runing one like 8.5 with no problem if you want the plain i can give them to you if you email me