Third Fresher’s  Workshop
Basic Parts Of A Mobile Robot <ul><li>Locomotion system </li></ul><ul><li>Power supply system </li></ul><ul><li>Actuators ...
 
Potentiometer
Capacitors
IR LED
LED: an inner view
Diode
Current Flow in a Diode
Multimeter
POWER SUPPLY  (RECTIFIER CIRCUIT)
IC7805/ IC7812 1 - Input  2 - Ground  3 - Output
THE RECTIFIER CIRCUIT
USES OF RECTIFIER CIRCUIT <ul><li>To convert Alternating Current to Direct Current. </li></ul><ul><ul><ul><li>We get Alter...
STEPS OF CONVERTING AC TO DC <ul><li>First the Transformer, converts 220V AC to 12V AC. </li></ul><ul><li>The Diodes recti...
End Actuators <ul><li>They convert the electrical energy into meaningful mechanical work </li></ul><ul><li>Mechanical outp...
Motors are of various kinds <ul><li>AC Motors : Not used much in robotics </li></ul><ul><li>Stepper Motors : For controlle...
DC Motors <ul><li>As the name suggests, a motor which uses a DC (Direct Current) power </li></ul><ul><li>Can run in both d...
DC Motor Working  <ul><li>Direction of rotation controlled by polarity of current / voltage </li></ul><ul><li>Speed of rot...
DC Motor Specifications <ul><li>Operating Voltage : Recommended voltage for powering the motor </li></ul><ul><li>Operating...
DC Motor Characteristics <ul><li>Free running torque & current are ideally zero </li></ul><ul><li>Increased load implies, ...
DC Motor Characteristics <ul><li>Zero speed at maximum load (stall torque) </li></ul><ul><li>Highest speed while free runn...
DC Motor Drivers <ul><li>These are current amplifying circuits </li></ul><ul><li>A low current control signal is converted...
DC Motor Direction Control <ul><li>H – Bridge Circuit Diagram </li></ul>S 1 S 3 S 2 S 4 M 1 2 V CC
H – Bridge Working
Electronic Direction Control <ul><li>H – Bridge Circuit Diagram </li></ul>
Sensors <ul><li>Analogous to human sensory organs </li></ul><ul><ul><ul><li>Eyes, ears, nose, tongue, skin </li></ul></ul>...
LDR - Light Dependent Resistor <ul><li>Made of cadmium sulphide </li></ul><ul><li>Resistance between two terminals vary de...
Comparator
<ul><li>Light Sensing Module using LED-LDR combination </li></ul>Sensor   Interfacing
Bump Detector Module
An Example - Line Follower <ul><li>A line follower is a robot capable of tracking a line drawn on a surface </li></ul><ul>...
Block Layout of Line Follower
Line Following Algorithm All the sensors are assigned  some weight such as Sensor 1 = a1 = 3 Sensor 2 = a2 = 2 Sensor 3 = ...
DC Motor Speed Control Circuit <ul><li>Input is the operating voltage & control signal </li></ul><ul><li>Output is a part ...
DC Motor Speed Control Cont… <ul><li>Controlling the current by passing it through a variable resistor is not advisable as...
Duty Cycle Fundamentals
Duty Cycle Contd… <ul><li>The time period (τ) is the duration after the voltage waveform repeats itself </li></ul><ul><li>...
<ul><ul><ul><li>Pulse Width Modulation </li></ul></ul></ul><ul><li>PWM is a technique using which we can modify the duty c...
L293D – Pin Diagram
THANK YOU
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Third Freshers\' Workshop 2011

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Third Freshers\' Workshop 2011

  1. 1. Third Fresher’s Workshop
  2. 2. Basic Parts Of A Mobile Robot <ul><li>Locomotion system </li></ul><ul><li>Power supply system </li></ul><ul><li>Actuators </li></ul><ul><li>Sensory devices for feedback </li></ul><ul><li>Sensor Data processing unit </li></ul><ul><li>Control system </li></ul>
  3. 4. Potentiometer
  4. 5. Capacitors
  5. 6. IR LED
  6. 7. LED: an inner view
  7. 8. Diode
  8. 9. Current Flow in a Diode
  9. 10. Multimeter
  10. 11. POWER SUPPLY (RECTIFIER CIRCUIT)
  11. 12. IC7805/ IC7812 1 - Input 2 - Ground 3 - Output
  12. 13. THE RECTIFIER CIRCUIT
  13. 14. USES OF RECTIFIER CIRCUIT <ul><li>To convert Alternating Current to Direct Current. </li></ul><ul><ul><ul><li>We get Alternating Current as Power Supply in our homes, but electronic components in robots use Direct Current. </li></ul></ul></ul>
  14. 15. STEPS OF CONVERTING AC TO DC <ul><li>First the Transformer, converts 220V AC to 12V AC. </li></ul><ul><li>The Diodes rectify the current in a single direction. </li></ul><ul><li>The Capacitor then normalizes the current. </li></ul><ul><li>The little distortions are further rectified by the IC7805. </li></ul>
  15. 16. End Actuators <ul><li>They convert the electrical energy into meaningful mechanical work </li></ul><ul><li>Mechanical output can be rotational or linear (straight line) </li></ul><ul><li>Motors provide rotational motion </li></ul><ul><li>Electromagnets provide linear motion </li></ul>
  16. 17. Motors are of various kinds <ul><li>AC Motors : Not used much in robotics </li></ul><ul><li>Stepper Motors : For controlled rotation </li></ul><ul><li>DC Motors : Finds extensive general use </li></ul><ul><li>Servo Motors : DC motor with in built feedback & error compensation </li></ul>
  17. 18. DC Motors <ul><li>As the name suggests, a motor which uses a DC (Direct Current) power </li></ul><ul><li>Can run in both directions </li></ul><ul><li>Speed Controllable </li></ul>
  18. 19. DC Motor Working <ul><li>Direction of rotation controlled by polarity of current / voltage </li></ul><ul><li>Speed of rotation controlled by average energy (power) fed to the motor </li></ul>
  19. 20. DC Motor Specifications <ul><li>Operating Voltage : Recommended voltage for powering the motor </li></ul><ul><li>Operating Current : Current drawn at a certain load on the shaft </li></ul><ul><li>Stall Current : Maximum current drawn, when motor not allowed to rotate </li></ul><ul><li>Stall Torque : Rotation force needed to hold the motor in stall condition </li></ul>
  20. 21. DC Motor Characteristics <ul><li>Free running torque & current are ideally zero </li></ul><ul><li>Increased load implies, increased torque, current drawn & power consumption </li></ul><ul><li>Power supplied by a motor is the product of output shaft’s rotational velocity & torque </li></ul><ul><li>DC Motors are high–speed, low-torque devices </li></ul><ul><li>Using gears, the high speed of the motor is traded off into torque </li></ul>
  21. 22. DC Motor Characteristics <ul><li>Zero speed at maximum load (stall torque) </li></ul><ul><li>Highest speed while free running (zero load) </li></ul><ul><li>Highest power at half speed & half load </li></ul>
  22. 23. 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 ICmax is usually of the order of Amps as compared to small signal transistors which have ICmax in mA </li></ul>
  23. 24. DC Motor Direction Control <ul><li>H – Bridge Circuit Diagram </li></ul>S 1 S 3 S 2 S 4 M 1 2 V CC
  24. 25. H – Bridge Working
  25. 26. Electronic Direction Control <ul><li>H – Bridge Circuit Diagram </li></ul>
  26. 27. Sensors <ul><li>Analogous to human sensory organs </li></ul><ul><ul><ul><li>Eyes, ears, nose, tongue, skin </li></ul></ul></ul><ul><li>Sensors help the robot knowing its surroundings better </li></ul><ul><li>Improves its actions and decision making ability </li></ul><ul><li>Provides feedback control </li></ul>
  27. 28. LDR - Light Dependent Resistor <ul><li>Made of cadmium sulphide </li></ul><ul><li>Resistance between two terminals vary depending on the intensity of light </li></ul><ul><li>Can be used to differentiate contrast colours </li></ul>
  28. 29. Comparator
  29. 30. <ul><li>Light Sensing Module using LED-LDR combination </li></ul>Sensor Interfacing
  30. 31. Bump Detector Module
  31. 32. An Example - Line Follower <ul><li>A line follower is a robot capable of tracking a line drawn on a surface </li></ul><ul><li>Optical sensors capture the line position at the front end of the robot </li></ul><ul><li>The robot is steered to keep it always over the line </li></ul>
  32. 33. Block Layout of Line Follower
  33. 34. Line Following Algorithm All the sensors are assigned some weight such as Sensor 1 = a1 = 3 Sensor 2 = a2 = 2 Sensor 3 = a3 = 1 Sensor 4 = a4 = -1 Sensor 5 = a5 = -2 Sensor 6 = a6 = -3
  34. 35. 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>
  35. 36. 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>
  36. 37. Duty Cycle Fundamentals
  37. 38. Duty Cycle Contd… <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>
  38. 39. <ul><ul><ul><li>Pulse Width Modulation </li></ul></ul></ul><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>
  39. 40. L293D – Pin Diagram
  40. 41. THANK YOU

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