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Transistor based line following robot help

Discussion in 'General Electronics Discussion' started by applehusky, Jul 4, 2015.

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  1. applehusky

    applehusky

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    Jul 4, 2015
    Hello all
    I'm new here, and somewhat new to electronics.
    A few days ago I set out to build a line following robot as a thing to keep my brain occupied in between semesters. I've got the chassis down no problem, but the circuitry is giving me a bit of a headache.
    I'm going off of this schematic here:
    [​IMG]
    But instead of using a photoresistor, I'm using a phototransistor because that's what's in the QRB1114 sensors I had lying around. The way I have it set up, I get voltage when the sensor is over white paper and none when it's over black paper, but when I add the motor to the circuit, the meter reads 0.00v and the motor doesn't turn. I have a feeling that this is a stupid mistake on my part and there's a simple answer but I can't, for the life of me, figure it out. So anyone who has some knowledge in this area, or has done a similar project, please let me know your thoughts. Thanks a bunch ^^
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Hello
    How have you connected your photo transistor? Can you draw a new circuit diagram showing how it is connected?
    Adam
     
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Ah ok I just looked at the datasheet for the device and you are going to have problems. This device is designed to be optically tuned to the transmitter which is Infrared. You have a white LED which is not Infrared, it also has a daylight filter which is going to further reduce the output.

    The device can't supply enough current to the transistor when you add the motor because the detector is not receiving enough Irradiance of the correct wavelength of light. You could try removing the device from it's holder and look at using a transistor with a higher gain. But this still might not work.

    Adam
     
  4. applehusky

    applehusky

    2
    0
    Jul 4, 2015
    It turns out I had it wired up wrong. the diode was not connected properly. Thanks for asking for a schematic. Made me check over my work and notice it.
     
  5. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Ok no probs, thought I was onto something then :)
    Adam
     
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