Sensors

 

The electromagnetic spectrum

 

 

  Photoresistors or photocells - Visible Light

 

      RWP has 2

      As light intensity increases, resistance in photocell decreases and V_out increases

         Using ohm's law and a voltage divider

         Voltage Divider Circuit:  V_out = V₁xR₂/(R₁ + R₂)

         R₂ is fixed in the system

         R₁ varies depending upon incident light, V₁ is voltage applied (batteries)

      Voltages in range 0.0 to 5.0 volts are converted to numbers in range from 0 to 255

        (256 values, 2⁸ = 256 in RWP's 8 bit system)

      LED reports current analog values - L or R photocell and resistance value

      Photocells vary in sensitivity - point toward while sheet of paper

      Cover part of more sensitive cell with black tape so are approximately equal in

         sensitivity

 

  IR Emitters and Receiver - IR Light

 

      Detect obstacles, not distance to the obstacle

      RWP has 2 emitters and 1 detector

      Adjustments

        To maximize detection distance: Move white paper in and adjust potentiometer

        To prevent false readings - black tape

 

  Sound Sensors

 

       Adjustable in terms of sound pitch and duration

       RWP has 1

  Bump Sensors

 

      Works on principle of open and closed circuit

      RWP has 3