# Simple (no solder or resistor) LED light



## childofthenight (Aug 24, 2007)

thanks cassie7, never thought of that, I always soldered, great idea!!


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## Cassie7 (Sep 5, 2007)

Someone on another forum asked me about the battery life. I have read that it's supposed to last about two weeks but I'm doing my own test. I lit one last night at 10PM EST and will let you all know when it dies


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## LV Scott T (Aug 14, 2007)

I see the battery is 3v. What is the voltage rating of the LEDs you buy?


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## Cassie7 (Sep 5, 2007)

Honestly, I don't know.


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## Cassie7 (Sep 5, 2007)

Well, whoever said that they last about two weeks was daft unless they turned them on for only a few hours each night.

I lit one at 10PM on Wed night and today at 5PM (Sat), it's visually on it's last legs after running 67 hrs straight. If you look at it, you can still see that it's lit but when I first fired it up, it cast a fairly bright beam of light on the wall about 2 feet away. I see no light on the wall at all now.


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## LV Scott T (Aug 14, 2007)

Well, sounds like if you ran it for 4 hours each night (6:00 - 10:00), it would last a couple of weeks. What more could you ask for? I still like the idea and will probably use it next year. Thanks!


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## Cassie7 (Sep 5, 2007)

Mine is still glowing faintly


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## Lady Nyxie (Jul 27, 2006)

Thanks for helping those of us who are lazy and/or technologically challenged.


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## dionicia (Nov 5, 2006)

I saw someone doing this with magnets. They were using them to throw on metal buildings and bridges. If I saw that stuff, I would ask the city if I could remove them. Look ma, free LEDs!


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## ylbissop (Sep 6, 2007)

dionicia said:


> If I saw that stuff, I would ask the city if I could remove them.


noone as far as i know has asked any city if they can use led throwies the concept behind the idea was to be a form of graffiti so I don't see any need to ask them if you can take them down. you can get more info on the origin and how to exc plus some other neat projects here.


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## dionicia (Nov 5, 2006)

Better to get permission than to be accused of putting them up there. Why take a chance.


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## DetroitGrass (Sep 15, 2007)

Okay. This is a bad practice. 
The resistor limits the amount of current.
You should limit the amount of current, it will make the battery last longer.

Also, by not doing it, you are messing up circuit equations (power/heat is being used that you dont want to be used)

So you have your 3 volt battery. All the voltage will equal each other.

Battery = Forward voltage of the LED + wire drop + resistor drop. 
3 V = 2.2 V + .8 + 0

The 2.2 V is assumed, you would need to check the data sheet. This set up means your little wire that is not rated for .8V with who knows how much current (which could blow up your LED).

Better approach.
Battery = Forward voltage of the LED + wire drop + resistor drop. 
3V = 2.2 V + 0 V + 0.8 V
Now, here we make the resistor soak up all the power. Lets demand that we want 20 mA. 
V = I x R
R = 0.8 / 20 ma = 40 ohms (In reality, you would pick 39 Ohms as its the closest value at 10 percent ) http://www.rfcafe.com/references/electrical/resistor_values.htm

Power of resistor = I * I * R = 0.02 * 0.02 * 40 = 0.016
so a 1/4 (or under 0.25) watt resistor would be fine.

Now just for kicks, if you could add a duty cycle (turn on and off the battery quickly) your eyes will not notice that it is off and you can make the battery last even longer.

Heres more reading and a calculator if the above makes no sense.

http://www.rc-cam.com/led_info.htm


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## LV Scott T (Aug 14, 2007)

So anyway, like we were saying...


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## Elza (Jun 21, 2004)

This led idea is going to help me out if you really do get that beam on light on the wall at first. Here's why....I have the motion activated laughing mirror that I hang in the bathroom over the toilet at my parties (sorry guys...I just think it's funny) anyway, if the lighting is not right it won't trip. I have had to get creative in the past and come up with an alternative light source, because I don't want to have to use full lighting during my party. I've never be totally happy with the result. Most of those motion activated things almost require you to waive you hand in front of the sensor...not very subtle. I am going to try it out...maybe a well placed led will do the trick...Thanks for the idea


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## ylbissop (Sep 6, 2007)

Elza said:


> This led idea is going to help me out if you really do get that beam on light on the wall at first.


a keychain or pen flashlight(LED or bulb) or dollar store or vending machine lazer pointer might be a cheaper simpler option that will last longer. most of the cheap motion detectors work off of the change in light you can test the prop by turning it on in the most completely dark room/closet you can find. with the lights still off does it still work? also if its started in a dark room if you flip the light on in the room after its started does it go off? if it dosen't go off in the dark or goes on when light is introduced it may work to simply point the tightest beam of light you can create at the censor that will be broken when someone walks in front of it like this:

lightsource-------->person----->censor on prop

in some cases it even works just to put a lamp or candle directly opposite so a person approaching casts a shadow onto the censor but it depends on the censors range and how it is housed allot of the props i've seen have the censor buried in a deep whole which makes them less effective as less light gets to them.

if the dark room dosen't work you may be dealing with a Infrared or laser detector in witch case it wont ever help to point a light at it.

a led flashight of the same price would have a much longer shelf life than a throwie LED's arn't like light bulbs and can last forever if used right. like DetroitGrass pointed out you wont have to keep buying new batteries for it and new LED's when they heat up and melt to death.


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## Crunch (Oct 23, 2008)

Lady Nyxie said:


> Thanks for helping those of us who are lazy and/or technologically challenged.


This is great for someone without the knowledge of circuit boards, soldering irons and resistors or all of the above. If I can pull of a corpse skull like the one DrKreepy made in his video on Youtube and put LED's in the eye sockets and have that inside the hood of my big hanging decoration, I would be happy with that.


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## SilentRequiem (Dec 19, 2008)

sweet, cassie! just the stupid siple kind of thing needed for a person like me ^^ (electricity doesn't llike me) very creative, i'm most definitely using this!


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