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itwannabee

Member - Posts: 4

Joined: July 20, 2006

Location: United States

Posted: July 20, 2006 at 1:01 AM / IP Logged

I'm new to the board and very interested in LEDs. I've been searching for a "how to" link on LEDs. i was wondering, is there a sticky on basic LEDs on the board?

First off, i'd like to start a project with LED. I made a design with plexiglass and would like to turn it into a night light using LED plugged into an outlet at home. is this even possible?

can someone please direct me towards the right direction.

Thanks for your input.

stealthone

Member - Posts: 26

Joined: April 01, 2006

Location: United States

Posted: July 24, 2006 at 4:15 AM / IP Logged

Well, here is a start:

The BASICS:

1. Match the LED color to the LENS color - that way there will be no illumination loss through changing color wavelengths

2. Yellow & Red LED's forward voltage drop is 1.8-2.4 volts giving you an average 2 volts per LED (6 in series equals 12volt (10.8-14.4v working range))

3. Blue & White LED's forward voltage drop is 2.4-3.5 volts giving you an average 3 volts per LED (4 in series equals 12 volt (9.6-14.0v working range))

4. Always put a current limiter (resistor) in each series of LED's in both of the above cases 60 ohm 1/4 watt works fine for car use

5. You can parallel as many of the above series as you like (or will fit the enclosure)

Hope that helps

markcars

Silver - Posts: 662

Joined: December 11, 2002

Location: New York, United States

Posted: July 24, 2006 at 9:17 AM / IP Logged

In addition to that, here's a link to some more info on LEDs http://wolfstone.halloweenhost.com/Lighting/litled_LightEmittingDiodes.html

kardain

Member - Posts: 15

Joined: April 08, 2006

Location: United States

Posted: July 24, 2006 at 9:27 AM / IP Logged

Here's a calculator in case you are using a different color other than mentioned above:

http://led.linear1.org/led.wiz

Sorry can't help on the A/C application as I'm not too sure.

Mad Scientists

Silver - Posts: 380

Joined: February 07, 2004

Location: United States

Posted: July 24, 2006 at 10:05 AM / IP Logged

For the AC, just use a 'wall wart'.. a plug in transformer that converts the wall AC to some DC voltage. LEDs will have two specs.. a Vf (voltage foward) and a current (often 0.020 amps, also known as 20 millamps). You will need to use a current limiting resistor.. calculate what value you need like this.

Start with your DC supply voltage.. for this example lets say it's 6vdc. The LED specs are foward voltage of 1.2v and current of 0.020 amps. You are going to be building a voltage divider circuit..

Take your supply voltage and subtract the Vf of the LED.. 6.0v - 1.2v = 4.8v

Your resistor will have to drop 4.8 volts.. using something called Ohm's Law you can calculate what resistance you'll need to accomplish this.

Ohm's Law is Voltage = resistance * current

We have voltage = 4.8v and current of 0.020 amps.. rearrange the formula to find resistance.

Resistance = Voltage / current

? = 4.8v / 0.020 amps

Resistance = 240 ohms.

So get a resistor of 240 ohms (or something close) and wire it in series with the LED..

Ask if you've got any more questions..

Jim

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itwannabee

Member - Posts: 4

Joined: July 20, 2006

Location: United States

Posted: July 26, 2006 at 1:27 PM / IP Logged

thanks for the informations!!!

might take me a while to grasp all the info because i don't have any experience with LED and electrical stuff.

another information is that i'm not trying to install this in a car, it's going to my bedroom as a night light. just want to start a project with LEDs and when i get more experience, i'll do something with the car.

kardain

Member - Posts: 15

Joined: April 08, 2006

Location: United States

Posted: July 26, 2006 at 10:01 PM / IP Logged

Shoot me a PM if you have any questions down the road. I've done enough with D/C LED wiring (ie. car wiring) that I can do it in my sleep. :)

stealthone

Member - Posts: 26

Joined: April 01, 2006

Location: United States

Posted: July 29, 2006 at 6:12 AM / IP Logged

itwannabee wrote:

thanks for the informations!!!

might take me a while to grasp all the info because i don't have any experience with LED and electrical stuff.

Great project to start with!! Easy way to start is to find an old plug-in power supply (those black cubes that plug into the wall) that has a "Volts DC" (VDC) output higher than 3volts. When you find one PM me with the voltage and I can assist you if you would like.

ff-mike

Copper - Posts: 199

Joined: November 15, 2004

Location: United States

Posted: July 31, 2006 at 10:47 AM / IP Logged

stealthone wrote:

1. Match the LED color to the LENS color - that way there will be no illumination loss through changing color wavelengths

Preferably don't use any lens. A clear plastic lens will reduce the output of a light, strobe, or LED by at least 12%. Color matched lenses will reduce by at least 18%.

Furthermore, do not use a white LED if you don't want white lighting- besides costing more the output is seriously affected by using a colored lens over it.

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LEDs

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