lm3915 circuit question

Discussion in 'General Electronics Chat' started by zazas321, Nov 30, 2015.

  1. zazas321

    Thread Starter Member

    Nov 29, 2015
    99
    3
    http://www.uploadarchief.net/files/download/vu meter toerenteller.jpg
    Heyy. Im new to electronics. I have built 10 led vu meter and want to build 20 led meter^^.But i dont understand one thing- why theese resistors on both sides are connected seperately. I mean why cant 1k and 3,9k resistors be connected like one 4,9k? isnt thats the same?
     
  2. MrCarlos

    Active Member

    Jan 2, 2010
    400
    134
    Hello zazas321

    No, definitely is not the same as putting a resistance of 4.9K instead of two, one of 1K and another 3,9K.
    These two resistors form a voltage divider.
    With a single resistor how would you do ??

    This voltage divider is to program the IC 'Telling'
    what level of input voltage at PIN 5 turn ON the LED connected to PIN 1.
    And
    what level of input voltage at PIN 5 turn ON the LED connected to PIN 10.
    It is to the measurement range.

    Keep an eye to the attached PDF document.
     
  3. zazas321

    Thread Starter Member

    Nov 29, 2015
    99
    3
    but those resistors are connected in series to each other arent they?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    The two resistors are to set the ref hi voltage and led current, see the datasheet...
     
  5. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Yes, but you're using a voltage from the divider.
     
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