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How to Connect to H Bridge?

Discussion in 'General Electronics Discussion' started by ashesv14, Feb 11, 2014.

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  1. ashesv14

    ashesv14

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    Feb 10, 2014
    I am building a robot line following. I want to use 4 LDR's. 2 to follow line and 2 to detect the background colour. This is because half side of the track is black and the other white. I am using comparator to detect the high and low voltage between the 4 LDR. But I am confused about connecting this comparator to the H bridge with outputs of the Hbridge being 2 motors. I want to make the robot as fast as possible this is possible by making one motor being clockwise and the other being clockwise. How can this be done using the Hbridge
     
    Last edited: Feb 11, 2014
  2. BobK

    BobK

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    It is a little more complicated than that. You want to change the direction by slowing one motor. And you need some logic. If both sensors are seeing white you want to slow one motor, and both are seeing black you want to slow the other. A microcontroller would be best.

    Bob
     
  3. ashesv14

    ashesv14

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    Feb 10, 2014
    I cant use micro controller for this project. Thats why I am getting stuck. By using microcontroller i could have programmed the microcontroller. Is there any other way to this problem with out using progammable components
     
  4. BobK

    BobK

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    Yep, you can use logic circuits.

    Oh, and why are you using an H-bridge? It should not be necessary if the robot only moves forward and it would complicate the logic to make it turn to stay on the track.

    Bob
     
  5. ashesv14

    ashesv14

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    Feb 10, 2014
    It has to take turns but not sharp turn maybe around 0 - 60 degrees turn.
     
  6. Arouse1973

    Arouse1973 Adam

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    I think what Bob means is it does not go backward so you don't need to reverse the current to the motors.
    Adam
     
  7. BobK

    BobK

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    Exactly, which means you can use a single MOSFET to control each motor, no need for an H-bridge.

    Bob
     
  8. Arouse1973

    Arouse1973 Adam

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    You could also add another transistor to switch the 0V and a brake Mosfet to supply power the 0V side to act as a brake when the 0V Mosfet is off. But you still don't need a full H bridge.

    Adam
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The placement of the LDRs with respect to the wheels is important.

    Obviously they should be on the center-line of the vehicle, but how far ahead or behind the axle? You would be wise to make this adjustable.

    Googling "White line follower" is going to give you a lot of information.

    Most old school white line followers used just 2 sensors. There may be reasons to use more, but they're probably not good ones if you're not experienced.

    The fact that you seem to be following an edge rather than a line makes little difference to the number of sensors needed. You need to invert the signal from one of your sensors (you could swap the resistor and LDR in the simplest case).
     
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