Schematic

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 Ohm resistor between Rg and Ground, sets an amplificaion factor of 1 + 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.