Electronics Resistors as Pull Down resistors with LEDs...

Discussion in 'Modding' started by Bogomip, 27 Mar 2003.

  1. Bogomip

    Bogomip ... Yo Momma

    Joined:
    15 Jun 2002
    Posts:
    5,161
    Likes Received:
    39
    hiya! im a bit confused as to working out the values of pull down resistors! this is what i have so far...

    PHP:
    The resistors in the system are Pull Down resistors. They are there so the LEDS do not burn out (as part of the current will go through the resistor too!).

    LED (approximations of a standard LED)
    V[forward] = 2V 
    I    [max] = 20mA
    R     = 100

    With Resistor…
        
        I     = V / R
        I     = 15 / 1100
        I     = 1.4mA

    Without Resistor 

        I     = V / R
        I     = 15 / 100
        I     = 150mA
    but im pretty sure i have done something wrong.

    Im working with a 15v supply and the pull down i have been experimenting with is 1k, but im quite unsure how to find out what the actual value is :)

    any help appreciated, thanks!
     
    Bogomip, 27 Mar 2003
    #1
  2. Oclocker

    Oclocker What's a Dremel?

    Joined:
    21 Jun 2001
    Posts:
    3,194
    Likes Received:
    5
    Its 15v-2v=13v

    13/0.02=650 Ohms

    A 1K ohm will give you 13ma which is usually plenty..
     
    Oclocker, 27 Mar 2003
    #2
  3. Bogomip

    Bogomip ... Yo Momma

    Joined:
    15 Jun 2002
    Posts:
    5,161
    Likes Received:
    39
    woo, thanks :) thats very helpfull :) i can now rest in peace that my LEDs are gonna be A OK! :)
     
    Bogomip, 27 Mar 2003
    #3

Share This Page