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LED string

Discussion in 'LEDs and Optoelectronics' started by colum, Sep 27, 2018.

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  1. colum

    colum

    155
    4
    Jul 25, 2013
    I have a mechanical arm that has 4 limit switches that is hooked up to 4 LEDs. 3 of the LEDs light up fine when activated but the last LED of the chain seems to take all of the power of the 9v battery when activated
    I have switched LEDs etc but always the last Led prevents the first 3 from lighting
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    What value resistors do you have in series with the LEDs?
     
  3. colum

    colum

    155
    4
    Jul 25, 2013
    Thank you for responding Steve...One resistor at input + 330 ohms....colum
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,505
    2,849
    Jan 21, 2010
    Let me guess, the last LED is red and the others aren't?

    You should have a separate resistor for each LED.

    Ok the basis of what you have now, four 1.2kΩ resistors should do the trick.
     
  5. colum

    colum

    155
    4
    Jul 25, 2013
    Thanks Steve, I did try a Red a Green and a Blue
    and thanks for the resistor placement and Ohm advice
    colum
     
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