Schematic

image0

A pendulum executes simple harmonic motion. If the anglular displacement is plotted against time, we get a sine wave. But angle encoders are costly, we can use a DC motor as angular velocity encoder, the induced voltage is proportional to the instantaneous angular velocity.

Instructions

  • The pendulum is attached to the axis of the motor.
  • The induced DC voltage is proportional to the angular velocity.
  • The signal is measured by A3. The 100 Ω resistor between Rg and Ground, sets an amplification factor of $1 + \frac{10000}{100} = 101$, it is required since the induced voltage is small.
  • Oscillate the pendulum and press START button to record the data.
  • If the signal is noisy, try rotating the whole body of the motor by several degrees and try again.