Robotix Tutorial 4

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Robotix Tutorial 4

  1. 1. TECHNOLOGY ROBOTICS SOCIETY Indian Institute of Technology, Kharagpur
  2. 2. A TUTORIAL ON ROBOTICS Motor Drivers
  3. 3. DC Motor Drivers <ul><li>These are current amplifying circuits </li></ul><ul><li>A low current control signal is converted into a proportionally higher current signal that can drive the motor </li></ul><ul><li>Power Transistors can switch high currents. The I Cmax is usually of the order of Amps as compared to small signal transistors which have I Cmax in mA </li></ul><ul><li>Example: L293d, L298, ULN2003 </li></ul>Copyright © Robotix Team, IIT Kharagpur
  4. 4. DC Motor Direction Control <ul><li>H – Bridge Circuit Diagram </li></ul>Copyright © Robotix Team, IIT Kharagpur S 1 S 3 S 2 S 4 M 1 2 V CC Power Transistor Switches
  5. 5. H – Bridge Working Copyright © Robotix Team, IIT Kharagpur S1 S2 S3 S4 Current Direction Effect 1 0 0 1 1 to 2 Motor spins forward 0 1 1 0 2 to 1 Motor spins backward 1 1 0 0 - Braking Occurs 0 0 0 0 - Free running
  6. 6. DC Motor Speed Control Circuit <ul><li>Input is the operating voltage & control signal </li></ul><ul><li>Output is a part of the operating voltage depending upon the control signal </li></ul>Copyright © Robotix Team, IIT Kharagpur
  7. 7. DC Motor Speed Control Cont… <ul><li>Controlling the current by passing it through a variable resistor is not advisable as it is extremely energy inefficient </li></ul><ul><li>A trick is done to achieve reduced average power </li></ul><ul><li>Power is supplied to the motor in short intermittent bursts, as explained further </li></ul>Copyright © Robotix Team, IIT Kharagpur
  8. 8. Duty Cycle Fundamentals
  9. 9. Duty Cycle Cont… <ul><li>The time period ( τ ) is the duration after the voltage waveform repeats itself </li></ul><ul><li>Duty Cycle is the % time of τ , the voltage is equal to the operating voltage </li></ul><ul><li>The average voltage is equal to the ‘Duty Cycle’ % of the Operating Voltage </li></ul>Copyright © Robotix Team, IIT Kharagpur
  10. 10. Pulse Width Modulation <ul><li>PWM is a technique using which we can modify the duty cycle of a waveform depending upon an input control voltage </li></ul><ul><li>This forms the backbone of our speed control circuit </li></ul><ul><li>It can be easily implemented using the popular multipurpose IC 555, used widely for hobby electronics </li></ul>Copyright © Robotix Team, IIT Kharagpur
  11. 11. Both Speed & Direction Control Copyright © Robotix Team, IIT Kharagpur

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