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Discussion Starter #1
I am doing a rather elaborate build right now and one thing i would love to do is put 2 blue LED lights in a skull for eyes but I have NO CLUE how to wire LED lights for eyes...and get them to work. I am asuming someone is smarter than I when it comes to this.
 

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Funeral Crasher
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Do you just want two blue LEDs that you can insert through some drilled holes in the back of the skull eye sockets?

If you can't find a solution, let me know. I can solder up a circuit real quick and send it to you. I've got a bunch of blue LEDs.
 

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Monster guts used to sell pre wired LEDs that ran on a 9 volt battery. I didn't see them listed on their web site. But they might still sell them? I bought some from them the last two years and they were very inexpensive.
 

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Simple LED's are easy. The long lead is positive, short lead is negative, (the negative side of the LED also has a flat edge). LED's won't work if you connect them backwards, it won't hurt them but they won't light. Use a 470 ohm 1/4 watt resistor on each positive lead, this will work for voltage up 12VDC. You can use a 9v battery to power the pair or a wall wart power supply.
 

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I put together a video that helps explain a lot of this.
And, if you want my LED wiring calculator (a handy Excel spreadsheet), just drop me an email!
 

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Discussion Starter #9
BTW Thank you Creepy Creation for the tutorial. Not sure if the Board is needed or not but it gives me something to play with later
 

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As an LED beginner, that was excellent and simple, CreepyCreations.

My question: I knew someone who did an LED project once, wired about 25 LEDs in series, and put a resistor on every single LED (all same rated LEDs and resistors) I guess it was for safety because if you use one resistor up front and it fails, it could burn out the whole series of LEDs. Question is if this is overkill or a good strategy to use when wiring that many LEDs in a row.
 

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Overkill, if the first diode is blown, it will no longer make a circuit, meaning the subsequent diodes are safe. I am not an electrician, or electrical engineer.
 

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My question: I knew someone who did an LED project once, wired about 25 LEDs in series, and put a resistor on every single LED (all same rated LEDs and resistors) I guess it was for safety because if you use one resistor up front and it fails, it could burn out the whole series of LEDs. Question is if this is overkill or a good strategy to use when wiring that many LEDs in a row.
If they were in series it was overkill, also not sure if all the LEDs would have illuminated, I believe you meant in parallel then it is necessarily, series is where you take the negative side of a LED to the positive side of the next starting and ending at the battery, in parallel is where each positive side of the LED is on the positive side of the battery and the negative side of the LED is connected to the negative side of the battery.
 

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Yes, now I get it. It was in parallel, and therefore each would need its own resistor. Wiring in parallel is necessary so if one goes out, they don't all go out, right?

I guess if done in series, the power would be used up a few LEDs in, and the latter ones wouldn't light, correct?

Edit: nope, looked it up, voltage is spread evenly across the LEDs and therefore would be dim or not illuminated, as Caretaker mentioned.
 

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Yes, in parallel you need a resistor for every LED. You are correct... in a parallel setup, if one goes out, the rest stay lit. In series, if one burns out, the rest will go out (if the burn out results in an open circuit). If the burn out results in a short circuit, the rest will light up, just a bit brighter. That's another reason to go little bit high on the resistor value, to give you some "wiggle room" in such an event. Generally, though, LEDs don't burn out unless you really abuse them, so I usually don't bother with parallel. Parallel also becomes somewhat impractical if you have along string you want to run, since you now need long wires to run to each LED/resistor pair. Gets pricey, and I'm CHEAP!!! LOL
 

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I have an issue. I have a 3V 20 mA white LED (5mm) with a 1/4 watt 470 ohm resistor on the positive lead. With a 12v power supply attached, using a multimeter from the base of the LED (past the resistor) it reads 3.3v. Seems like that's too much and will cause early failure of the LED.

But the resistor should be 450 ohms = (12v-3v)/.02

Am I reading the voltage wrong? Should I be worried about how much voltage is running through the LED?
 

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I have an issue. I have a 3V 20 mA white LED (5mm) with a 1/4 watt 470 ohm resistor on the positive lead. With a 12v power supply attached, using a multimeter from the base of the LED (past the resistor) it reads 3.3v. Seems like that's too much and will cause early failure of the LED.

But the resistor should be 450 ohms = (12v-3v)/.02

Am I reading the voltage wrong? Should I be worried about how much voltage is running through the LED?
Don't worry about the voltage reading, the resistor is limiting the current. If you have a 470 ohm 1/4 watt resistor on that LED, you're fine and in no danger of burning it out. ;)
 

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Thanks! I already soldered and shrink wrapped a dozen, but to be safe I'm replacing them with 680 ohm resistors.

This is a long term project, once installed not easy (or impossible) to replace burned out LEDs
 

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Hi I wanted red eyes in my skeletons last year, I purchased a load of those small LED balloon lights, which you just turn to activate and can either have them static or flashing. They are only like tiny pellets, so I just cut the two eyes out and slotted them, were easily replaced when they ran out of battery with no wiring or electrics needed and they are very bright.

balloon lights.jpg
 
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