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Playing with LEDs

ImprovoloneImprovolone Registered User regular
edited March 2008 in Games and Technology
I have some projects in mind that I want to use LEDs for. Now, I've worked with breadboards and resistors before, but I know my math is going to need a brush up to make sure everything works out right. My biggest problem that I think I have at the moment, is where the hell should I get my materials? I still need to pick up a soldering iron, but I can get that anywhere.
What about the LEDs themselves? I know Radio Shack carries alot of stuff, but I also know that the internet provides a wealth of goods at cheap prices. I'm making some juggling props and would like these things to be on the very bright side. Any suggestions?
Also, any potential pit falls I'll be running into as someone who has never worked with LEDs before?

http://www.superbrightleds.com/leds.htm for instance has a list of what they carry. The intellect in me says the higher the luminous intensity, the brighter it is. Okay, great, but why is the other information important to me?

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Posts

  • mcphorks5mcphorks5 __BANNED USERS regular
    edited March 2008
    The only thing i know about leds is that now they can use salmon sperm to make them brighter then ever. http://www.engadget.com/2008/03/11/salmon-sperm-used-to-intensify-leds-grossify-everyone/

    mcphorks5 on
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  • BallmanBallman Registered User regular
    edited March 2008
    Really, LEDs are remarkably easy to use. Just keep a couple of things in mind (I'm going to simplify a lot here, since I don't know how many circuit basics you know):

    LED stands for Light Emitting Diode, and diodes are generally built to pass current only one way. There are exceptions, but that should get you started. If you click one of those spec sheets in the link you provided, it shows two leads (connections) for the diode in the diagram. The longer one is the anode, and is the one that should be connected to the positive terminal on your power supply. If you connect it backwards, it won't work, or in extreme cases, you can burn up the LED. If you want to lower the brightness of the LED, you can put a resistor in series either before or after the LED. If you want to raise the brightness, you can increase the supply voltage. Of course, the higher you go, the more likely you are to burn out the LED.

    That should cover it. I apologize if this was too simple, but I figured it couldn't hurt.

    Ballman on
  • evilmrhenryevilmrhenry Registered User regular
    edited March 2008
    (I'm assuming you want white leds, as that's what I've worked with before.) If you connect N white leds to N AAA batteries, everything should "just work". (I think the leds have to be in series, and the batteries in parallel, but don't quote me on that.) Anyway, this is the trick many cheap led flashlights use.

    Technically, AAA batteries put out 1.5 volts, and white leds expect 1.2 or something, but for most purposes, this is close enough, and means you don't need any resistors or voltage adjustments. This can be adjusted for use with other colors, by the way, but you need to change the numbers...

    Radioshack carries leds (the website says $5/white led, which is very high). You can also grab them from dollar-store keyring squeeze flashlights, (The kind built around a button battery. This is also a source for CR-2032 batteries.) or online if you need a lot of them.


    As for the site in question...
    Viewing angle: most leds are focused in a certain direction. If you point a single led in a direction, that's the angle that will be lit up.
    Wavelength: A more precise way of stating the color.
    Everything else seems obvious. The 5mm leds are the common size for leds.

    evilmrhenry on
  • ecco the dolphinecco the dolphin Registered User regular
    edited March 2008
    Depending on the quantity you intend to purchase, you might want to give Digikey a shot. Here's a direct link to the LED section (I hope it works).

    The range of options may overwhelm you, but to help you filter out certain ones that you'll most likely be unable to use, select:

    1.) In stock
    2.) Mounting Type -> Through Hole
    3.) Package/Case -> Radial (only Radial, not 3-lead or 6-lead unless you're looking for something fancy)

    and then select the colour you want.

    Shipping costs are here.

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  • ImprovoloneImprovolone Registered User regular
    edited March 2008
    Is Millicandela rating how bright it will be, assuming enough voltage? Or is that Luminous Flux?


    Adendum: How do multicolored LEDs work?

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  • Serious_ScrubSerious_Scrub Registered User regular
    edited March 2008
    Various Hong Kong based websites sell packs of 20+ LEDs for less than the price of one LED in Radioshack, if you are willing to wait about two weeks for shipping. I've been meaning to make a sensor bar with some IR LEDs, but I haven't found the time to get around to that

    Serious_Scrub on
  • evilmrhenryevilmrhenry Registered User regular
    edited March 2008
    Is Millicandela rating how bright it will be, assuming enough voltage? Or is that Luminous Flux?


    Adendum: How do multicolored LEDs work?

    The multicolored ones have 3 leds of the appropriate colors imbedded, along with a controller to switch between them. See http://www.dansdata.com/gz065.htm for lots more info.

    evilmrhenry on
  • acidlacedpenguinacidlacedpenguin Institutionalized Safe in jail.Registered User regular
    edited March 2008
    I used to get all my LEDs from lsdiodes.com but they've since stopped selling them.

    try http://www.mouser.com/

    they stock 14,000 different LEDs and have bulk savings.

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  • strebaliciousstrebalicious Registered User regular
    edited March 2008
    You know how to read a wiring diagram?

    I use http://led.linear1.org/led.wiz when throwing together LEDs. Got to know the specs on the light but this will tell you the most efficient way to put them together.

    strebalicious on
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  • elizabexelizabex Registered User regular
    edited March 2008
    I'm in Chicago, and there's this great store here called American Science and Surplus at which you can get all sorts of electronic components on the cheap ---- I've snagged materials for LED arrays, contact microphones, and other things. I believe you can order online too:

    http://www.sciplus.com/

    ..and yes, confirmed they do sell LEDs in packages of 4, 8, and 12.

    elizabex on
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  • SiliconStewSiliconStew Registered User regular
    edited March 2008
    I'll second Digikey and Mouser for EE supplies.


    The simplest LED circuit needs a power supply (voltage V), a resistor (resistance R in Ohms) and an LED in series.

    Look on the LED's datasheet for Forward Voltage (Vf) and Forward Current (If). You don't want your circuit to supply more than the LED's rated continuous forward current or it will burn out.

    What we really need to calculate here is the value of the resistor required.

    For this series circuit:
    V(supply) = V(resistor) + Vf(led)
    I(supply) = I(resistor) = If(led)

    For example if: V(supply) = 6V, Vf(led) = 3.4V, If(led) = 20mA

    V(resistor) = 6 - 3.4 = 2.6V
    I(resistor) = If(led) = 20mA

    Using V = I * R:
    R = 2.6 / .020 = 130 Ohms


    You might also want to calculate the power rating for the resistor

    P = V^2 / R = I^2 * R = V * I = 2.6 * .020 = 52mW

    So a standard 1/4 W resistor will be fine.


    Basically, any size power supply will work as long as you make sure the LED gets the correct current by choosing the right resistor.

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  • Big DookieBig Dookie Smells great! Houston, TXRegistered User regular
    edited March 2008
    I admit that I know little about LED characteristics, but why is the forward voltage (I assume that's the same as turn-on voltage) so high? I know that for regular diodes, the turn-on voltage is usually something like 0.6 or 0.7 V, but on those data sheets, many of them seem to be in the 3 V range. If that's the case, you'd almost have to place the diodes in parallel with the voltage source just to have enough voltage to turn on each diode. For any reasonable voltage source, I couldn't see you putting more than two diodes on each branch. Am I missing something here, or do LEDs really have that high of a turn-on voltage?

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  • SiliconStewSiliconStew Registered User regular
    edited March 2008
    Big Dookie wrote: »
    I admit that I know little about LED characteristics, but why is the forward voltage (I assume that's the same as turn-on voltage) so high? I know that for regular diodes, the turn-on voltage is usually something like 0.6 or 0.7 V, but on those data sheets, many of them seem to be in the 3 V range. If that's the case, you'd almost have to place the diodes in parallel with the voltage source just to have enough voltage to turn on each diode. For any reasonable voltage source, I couldn't see you putting more than two diodes on each branch. Am I missing something here, or do LEDs really have that high of a turn-on voltage?

    It depends on the color, size, and brightness but they are higher than a standard silicon diode.

    SiliconStew on
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  • ImprovoloneImprovolone Registered User regular
    edited March 2008
    You guys have been a ton of help so far, thanks.

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