Help with optical sensor

Discussion in 'Homework Help' started by phyton, Apr 11, 2016.

  1. phyton

    Thread Starter New Member

    Apr 11, 2016
    I am very new to electronics, and have been asked to desingg a extremely simple system that only contains a relfective optical sensor( link datasheet below)

    My Vcc is 5 volt

    i know i need two resisitors

    One resistor load connected to the photodiode calaculated with Rl= (vcc-vf)/If

    and another connected to the emitter of my transistor(With Ie= 100uA and Vec = 5 v) I am not sure which formula to use to calculate this resistor?

    I am not sure if finding the load line is neccesary for this? and how if so? I'd really apreciate some help since i'm in quite of a pinch on this one :)
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Welcome to AAC!
    Few of us here have a crystal ball to see your circuit :rolleyes:. Post a schematic to give us a clue, then perhaps we can offer guidance (but we don't do your homework for you).
  3. phyton

    Thread Starter New Member

    Apr 11, 2016
    Ok i can't get it on my laptop(handrawn)
    But it's very similar to this design were the values for the resistors R1 and R2 are unkown.
    Key difference is that the optical sensor isn't the same, beyond the specifications the difference is that the transitor and diode are opposite each other(cathode is next to the collector)
    I assume i can just treat it the same way if i connect the source vcc to the collector leg and connect emitter to ground.
    But the question is how i find the value for R2
  4. RichardO

    Well-Known Member

    May 4, 2013
    Have you looked at the graphs on pages 3 and 4 of the Vishay data sheet?
  5. MaxHeadRoom


    Jul 18, 2013
    You got your answers on EP.?