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Discussion in 'Electronic Basics' started by [email protected], Apr 8, 2005.

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  1. Guest

  2. James Beck

    James Beck Guest

    Sounds like it has the resistor already in there, so no, you don't need
    to add one. That is assuming the RS info is correct.

  3. Lord Garth

    Lord Garth Guest

    In typical Rat Shack style, they don't really tell you what you need to know
    BUT, no LED
    I have ever seen drops 12 volts in forward bias (Vf). So this unit has a
    dropping resistor
    in the package which looks like you can see it through the case.

    Don't let these guys rip you a new one! That red LED and resistor is poor
    quality at best
    50mcd at 45 degrees. Their cost is probably all of 2 cents. Get an LED
    from some
    broken item and connect up a scavenged resistor. The color of the LED makes
    all the
    difference to the Vf and that's the number needed to calculate the value you
    need. For just
    a quick test, pop on a 470 Ohm resistor and hook up to your 12 volts. WATCH
    polarity, it is a DIODE after all!

    470 Ohms is yellow violet brown
  4. Bob Eldred

    Bob Eldred Guest

    Pay attention to this very complicated answer: NO! No resister is needed.
    Ready made lamps like this already have the resistor included inside and are
    rated for the required voltage, in this case 12VDC. There are versions of
    these lamps that have a diode and resistor for 120VAC, directly, no external
  5. Checking out the URL you provided, I found this component to have a build in
    680Ohm resistor already. So you can connect it parallel to the 12V fan. Be
    sure to connect it in the right direction. You may blow it it you connect it
    in reverse.

    petrus bitbyter
  6. John Smith

    John Smith Guest

    " Be sure to connect it in the right direction. You may blow it it you
    connect it in reverse."

    Why? Surely no current will flow, as the diode part of LED comes into play.
    What's going to blow it?
  7. Most LEDs can handle a maximum reverse voltage of 5V. So unless some
    precautions are taken, the LED wil get 12V reverse voltage which it cannot
    stand. Precautions may be a antiparallel diode or even a second LED
    antiparallel to the first. As I did not see this or any other provision
    mentioned in the specifications I advise to stay on the safe side.

    petrus bitbyter
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