Line follower : QRD1114+Arduino

Discussion in 'The Projects Forum' started by athonks, Apr 27, 2012.

  1. athonks

    Thread Starter New Member

    Apr 15, 2011
    4
    0
    Hello guys,

    I'm working on a project which has created many issues so far, but i managed to solve them, except the latest one:confused::
    A way to connect the 7 sensors to arduino w/o frying them or underpowering the board(Arduino Uno).

    So, i'm using 7 Fairchild QRD1114 sensors, in a reverse V shape and an Uno which has only 1(!) 5V output.My most uneasing problem is reading the what seems to me incomplete datasheet, which can be found here.
    What is the curent/voltage for the 3 pin(the anode of the sensor)? I see that the phototransitor uses 1.7V and a current of 50mA max, so are 20-22mA enough?
    I have no ideea to creating a schematic of 7 sensor,except using 2 other digital pins set to HIGH for 5v output, only for the phototransistor.

    Help would be much appreciated,
    Athonks.
     
  2. athonks

    Thread Starter New Member

    Apr 15, 2011
    4
    0
    Still can't figure out the normal voltage of the 3 pin. Ideas anyone?
     
  3. BSomer

    Member

    Dec 28, 2011
    433
    106
    According to the datasheet you pointed to the emitter of the device has a maximum forward current rating of 50mA. Looking further into the datasheet says that the maximum forward voltage of the emitter at 20mA is 1.7V

    So with those numbers in mind you need to know what your supply voltage is. You stated something like 5V from an Uno (Arduino?).

    5V supply - 1.7V emitter = 3.3V
    3.3V / 20mA = 165

    So unless I missed something, which may be possible, the safe voltage of the emitter is 1.7V at 20mA. Using your 5V supply you need a current limiting resistor of 165 ohms. You can safely use a 180 ohm 1/4 watt resistor which is a commonly available value.
     
  4. athonks

    Thread Starter New Member

    Apr 15, 2011
    4
    0
    YES,that was right, after much testing i managed to make an array of 6 qrd 1114 in a V shape, connected with the proper resistor, working properly!
    Thanks for the help
     
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