LED questions

Discussion in 'Homesteading Questions' started by Kenneth in NC, Oct 19, 2004.

  1. Kenneth in NC

    Kenneth in NC Well-Known Member

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    How do you wire them so that they don't go boom when you hook a 9v battery to power them?

    Where can I find the bigger bright white LED's?

    Do they make and where can I find some blacklight LED's? Red LED's?

    Thanks. I know someone on here will know. :D

    Kenneth in NC
     
  2. aaatraker

    aaatraker Well-Known Member

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    A friend who did a google search ,found sites that sold them, he was replacing his malibu lights with them They had direct replacements in different colors. Don't know site link.

    kurt
     

  3. John_in_Houston

    John_in_Houston Well-Known Member

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    To keep them from going boom, you have to put what's called a current limiting resistor in series with them. A 1000 ohm resistor should work, the values aren't all that critical.

    As for the rest, I'd try Radio Shack for the different LEDs, They certainly make Red LED's, don't know about blacklight.
     
  4. 12vman

    12vman Offgridkindaguy

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  5. gspig

    gspig Well-Known Member

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    LED's are polarized, meaning that there is a positive and negetive wire. You will also need a dropping resistor. E=I * R will get you the right resistor. E- voltage (9volts), I- current (the led package will state current used), solve the equation for R- your resistor value. Radio shack sells a few, e-bay has sellers, electronics parts stores.
     
  6. mamabear

    mamabear Well-Known Member

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    My son is an electrician and he gets his LEDs from eBay by the sackfulls. They are a lot less expensive than anywhere else. I just did a search on there and they have all the colors you were asking about. You might also find the resistor that you need on there.
    Have a great day!
    Mamabear
     
  7. degaston

    degaston Member

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    LEDs require about 20-30 milliamps of current to light, and cause a voltage drop of approx. 2 volts. Using Ohms Law, V = I*R, you can solve for the current limiting resistor that you need. R = ( 9 Volts - 2 Volts ) / 0.025 Amps = 280 Ohms. Any resistor value in that ballpark ought to work for you. LEDs are tolerant of overcurrent, but too much will shorten the diode's operating life if it doesn't fry the device outright.

    A 9 Volt battery is very inefficient for lighting one diode, since most of the power is dissipated by the resistor. A couple of AAs or AAAs in series (3V) would do the job just fine, with a smaller resistor of course (40 Ohms).

    I bought mine from Digikey online two years ago. Prices have fallen substantially since then. Ebay has hundreds of options, for a much better price. Just about all colors (wavelengths), intensities and fields of view are available, but the green, blue, white and ultraviolet ones will cost a lot more than the red, yellow and orange colors.