LED bulbs?

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DarenN
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LED bulbs?

Post by DarenN » Tue May 12, 2009 8:54 pm

i need to understand something about LEDs. basic electrical stuff, i guess, but i don't know anything about electricity. can anyone help?

if i have three 1.5 volt (AAA) batteries connected in series (end to end. positive to negative) it's a total voltage of 4.5 volts. right? lets say these three batteries are powering three LEDs. will the voltage capacity of each bulb be 4.5 volts??

can an LED be connected directly to a battery? or is something else required in the circuit, (besides a switch)?

thanks;
Daren.........
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realityguy
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Re: LED bulbs?

Post by realityguy » Tue May 12, 2009 9:12 pm

Thank Gawd you asked that question!Now I'm not the lone idjit wondering what the answers are! :lol: I was wondering the same thing.I want to decrease the lights to only two and wondering if 3 volts will do.However..I do have a couple 3bulb/2-AAA battery fixtures that don't seem to have any reduction as far as resistors,etc..just an on/off push button on the back.

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Maybe the LEDs come in different voltages..I don't know.The only problem with these is that they had a red lens..I figured I'd chuck the lens and have clear bulbs..wrong!The bulbs glow red also..Oh well,guess I live with red.. :lol:
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zelph
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Re: LED bulbs?

Post by zelph » Tue May 12, 2009 9:15 pm

I've been away from the leds for awhile. Last I remember the ones I was using were 3v. A resistor has to be used in line to reduce the battery voltage going to the led. I purchased led's off ebay that already had resistors attached to be operated on a 12v system(car) I used a 9 volt battery to operate them. I hope someone has the whole explanation for you/us.
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realityguy
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Re: LED bulbs?

Post by realityguy » Tue May 12, 2009 9:32 pm

A resistor has to be used in line to reduce the battery voltage going to the led
Zelph..I'm assuming you mean if the voltage supply(battery) you are using is MORE than 3 volts...
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zelph
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Re: LED bulbs?

Post by zelph » Tue May 12, 2009 9:35 pm

realityguy wrote:
A resistor has to be used in line to reduce the battery voltage going to the led
Zelph..I'm assuming you mean if the voltage supply(battery) you are using is MORE than 3 volts...
Yes, that's correct.
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irrationalsolutions
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Re: LED bulbs?

Post by irrationalsolutions » Tue May 12, 2009 9:35 pm

there are a few places you can go to look and it will explain the basics to you. there are a few videos on youtube here is the channel...

http://www.youtube.com/user/makemagazine

and here is the link to the website and they have a few small projects on there and some explinations on how to do them...

http://makezine.com/
“Do or do not... there is NO try.” Yoda

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realityguy
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Re: LED bulbs?

Post by realityguy » Tue May 12, 2009 9:49 pm

If anyone is interested..that small fixture I have is something for jogging ..has a belt(or hat brim?) clip on the back and an on/off/or flash button..weighs 25 grams with 2AAA batteries..and 31 grams with a full red reflector cover lens.I don't think I'd want to hike trails with the thing..but would provide some light in a tent or hammock..wish the LEDs were clear.. :cry: They'd probably put out a lot more light.2-3/8"x1-3/8"x1" or 7/8" thick without the front lens.It does have kind of a semi waterproof seal behind the clip-on lens.
I don't know who sells them..I got a couple at a thrift store for $1 each on the sale cards..
:mrgreen:
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irrationalsolutions
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Re: LED bulbs?

Post by irrationalsolutions » Tue May 12, 2009 9:57 pm

if you want to change out the red leds to white its not that hard you just need to know what the voltage is. ive never tried it but i would think all you would need to do is use a voltage multimeter. with the light on. after that all you need is a soldering iron and the right leds.
“Do or do not... there is NO try.” Yoda

Luke "Whats in (out) there?" Yoda "Only what you take with you."

Luke "I can’t believe it." Yoda "That is why you Fail.”

realityguy
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Re: LED bulbs?

Post by realityguy » Tue May 12, 2009 10:20 pm

I still don't know how much I really want to mess with it.i still want a flashlight that will use two extra AA larger batteries because I have to carry the dang things anyway with the digital camera...I do have another aluminum flashlight that doesn't weigh much but does have bright white leds,an aluminum tube body,and takes 3AAs...Bright enough for even trail use if I had to..or setting up a tent at night.I think I have a head one also that takes 2AAs..got check in all my junk. :lol:
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DaddyMnM
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Re: LED bulbs?

Post by DaddyMnM » Wed May 13, 2009 1:24 am

if i have three 1.5 volt (AAA) batteries connected in series (end to end. positive to negative) it's a total voltage of 4.5 volts. right? lets say these three batteries are powering three LEDs. will the voltage capacity of each bulb be 4.5 volts??
Daren, if you wire the LEDs in a row in series they will divide the 4.5 equally so each will drop 1.5 volts. If you wire them in parallel they will each drop 4.5V.
can an LED be connected directly to a battery? or is something else required in the circuit, (besides a switch)?
If the voltage is within the LED rating, yes. Otherwise, you need to add a current limiting resistor in series with the LED.

Here are a couple of useful links:

http://ourworld.compuserve.com/homepage ... en/led.htm
http://unclean.org/howto/led_circuit.html
http://www.theledlight.com/LED101.html

One more useful tidbit is Ohm's law: V = I X R

V = Voltage in Volts
I = Current in Amps (20mA = 0.020 Amps)
R = Resistance in Ohms

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