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555 Circuit Problem

Discussion in 'Electronic Basics' started by Jim Dye, Nov 16, 2005.

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  1. Jim Dye

    Jim Dye Guest

    I am trying out my first electronics project, a LED flasher that looks like

    http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm (The one with
    the 9V battery shown)

    I have found numerous examples of the same circuit around the net...but
    this one looks the clearest.

    I have C as 100uF, R1 as 1K and R2 as 22K. Using the calculator, that
    should have the LED flashing on and off for about 1.5 seconds each state.

    The LED is set to draw 10mA on 9V

    When I turn on the juice (9v --- and the reason I am writing)...the LED
    goes flashes as expected BUT

    1. It is very dim
    2. The 555 is smoking and melting the breadboard.

    I have tried several combinations using various intermediate steps for
    wiring the same result.

    Maybe someone with more experience could suggest something to look for.
     
  2. Bart

    Bart Guest

    I only mention this as you say its your very first electronics project.
    On the breadboard, the 555 chip must be placed strategically straddling
    the divider section so that there is no conductivity from any pin to any
    other pin through the breadboard. Also, lookup the datasheet for your
    555 chip to make sure its one that is OK with 9 volts.
    HTH
    Bart
     
  3. Lord Garth

    Lord Garth Guest



    Despite the flash, something is very wrong with your parts and / or your
    wiring.
    Please check the orientation of the 555 WRT pin 1, it is the pin to the left
    of the
    notch when viewed from above.

    Did you use a fresh 555?

    Did you verify the power supply is properly connected to the 555?

    Is the LED shorted or connected in reverse?

    Your LED needs 10ma @ 9v or 900 ohms, use 820 ohms

    The resistor should be gray red brown.
     
  4. Guest

    I think maybe you should try something easier. Have a look at this led
    flasher it only uses a few parts and isn't that fussy about things like
    voltage and component values.
    http://xedox.de/blinker.htm
    When I first tried to build an led flasher mine started smoking as well
    :)
     
  5. John Fields

    John Fields Guest

     
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