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Got two little xmas tress at Walmart, each tree had 12 small 3mm colored led's, thought they were white, didn't say, darn! They are all hooked to a battery box for $8 for the two. Be neat for lighting up a car, or using the bulbs to replace regular bulbs. Just got some from All Electronics that size and paid like $2 each! This was a MUCH better buy! Might get out there quick, if you want some cheap bulbs.
 

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I love LEDs.

I love cheap things:D

Got several boxes, each containing 18 little white LED's and a battery pack for $2 each at Menard's after Christmas last year.
 

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I checked out the instructables.com website. Alot of stuff on LED's. One that got my interest was covering an LED with hot glow and then shaping the hot glue, I think it was called hot glue diffuser.
Another guy showed how to make a flicker flame circuit.
 

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Wal*Mart sells a child's "Tiara" - - for the little girl that wants to be a Princess... I think it is in the party goods aisle - - it has 5 red LEDs in a circular pattern on a small PC card with a button battery and a small On/Off pushbutton. The plastic Tiara will break within 5 minutes of placing it on the childs head if not at that exact moment or just before as you attempt to assemble the sides to it... anyway, the lights blink in a circular pattern to make the jewels in the tiara sparkle. If you take the lights off what is left of the tiara, bend the leads of the lights so they all face each other near the middle of the PC card and then put it into a firebox or model of a camp fire the blinking evens out a bit and effectively represents a flickering fire. I think the tiara is 99 cents... not bad for a fire simulation.
 

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Good idea. Say, those LED sets are hooked to a 3 volt battery box. To use with track power instead, couldn't a guy wire 6 in series and they would get the right voltage without buring up? What size resistor would one us, or is one needed? Like to do that, if someone can advise me.
 

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They may be 3v leds. Easy way to tell is to hook one to a 1 1/2v battery. If it doesn't glow, it's a 3v led.

They usually want like 30mA current. So all you need to do is divide to figure the resistor.

L = Led voltage ( times number of LEDs if you wire them in series)
V = Volts you want to run them from
R = Value of the resistor

R = (V-L)/.03

The value of R isn't very critical. If it's a little higher than you figure, the LED's won't light as bright. If it's a little lower, they'll light brighter and will only last 10s of years instead of thousands. Of course, if the resistor is 0, they'll have a very short, but eventful life.


You probably want to multiply (V-L)*.03 to figure the watts of the resistor. If the Watts is something like .2 and you have a 1/8 watt resistor, it will get HOT.
 
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Posted By chrisb on 11/20/2008 3:23 PM
I checked out the instructables.com website. Alot of stuff on LED's. One that got my interest was covering an LED with hot glow and then shaping the hot glue, I think it was called hot glue diffuser.
Another guy showed how to make a flicker flame circuit.



That is a great place there Chris! Love it there.
Toad
 

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Posted By Jerry Barnes on 11/21/2008 4:40 PM
Noel,
The led's seem to burn out, the ones I'm using from xmas light string of LED's that I cut up is doing fine with the wiring in series. Guess I did something wrong, oh well....

Jerry

Hi Jerry... Not sure what you are using for voltage.. but if using on your track voltage.. then use a 560 ohm resistor in series .. if using more than that, just remember the white ones need about 3 volts and the red,green,yellow uses about 1/12 volts.. so the resistor has to take up the difference in voltage that you are using..

Easiest way to fine out is start with a 1,000 [email protected] 1/4 watt and see if it will light up.. then go down from there until you find the resistor that will work for you..

I make track signals that using 5 mm LED's off of tracks power, so I been using 560 ohms with no problems.. They will usually light up before my Trains moves.

Whats nice with LED's is I use two target signals ( LED) ..(One Red and One Green) so when I reverse the train to go backward it changes to Red target.
Also if you use a bi-LED ...you can get Red or Green just by reversing the polity of the DC voltage. But use a 330 to 560 ohm Resistor with them in series for track voltage..
So all in all.... Just experiment.. If you want to series LED's (if say a Red) and you are using 6 volts then you would fig 1-1/2 volt for each LED = 4 LED's and them you still should at least a 1 ohm resistor for a safety margin.

On my Head lights I use a White 5mm LED with a 560 ohm in series. It still takes about 4 to 5 volts to light up. Most of my USA Eng's move at about 3 to 4 volts. so it close.

Hope this help so you don't have to go into Ohms law and just use a trial and error to fits to your needs..
This works for us.
 

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Jerry.. Another thing is when soldering LED's leads is try to get a alligator clip or needle nose close to the LED light/package. This will make a heat sink. Doesn't take much to mess up the LED package with heat.
Year's ago I use to mess up about ever other LED by soldering and getting to much heat. Or...to much voltage on them.

Had to live and learn the hard way..
 

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Man Jerry
And to think I worship every word you say.....
 
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all LEDs should be run from a current source, a resistor from a higher voltage works well. 30 mA is a little much for most LEDs, a more typical rating is 20 mA max

Costco has a set of 100 warm white LEDs in a string for $15. From looking at the specs on the package, they run the LEDs at about 80 mW each, which is a little more than 20 mA. They are fairly bright but not as bright as the more expensive ones. They all come with a clear plastic diffuser but that can be broken off if needed. They would work well in building where you might need a lot of them and more typical currents would be a few mA anyway.

- gws
 

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Hmm. Where's the nearest costco?
 

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I used some of the 2.4v. 3mm, warm white LEDs, with difuser/refractor in a Sierra passenger car. Two of them is sufficient to light the car. I run them off the regular track power or MUd to battery power in the combine. I put a 1ooo Ohlm resister in series on each LED. There have been no problems. They use significantly less amperage than the original six incandescant bulbs [which were way too bright].
JimC.
 
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