To design a teaching material on pendulum motion for a college course, a simple device was fabricated with an L.E.D. and a photo-sensor. An X-T recorder was used to draw oscillation curves in simple pendulum motion. Each oscillation period was easily estimated from wave forms in regular intervals on the recording paper, and was also evaluated. The present study describes features of the equipment designed as a portable teaching tool for demonstration lectures. The utility drawing the oscillation curve on recording paper is briefly discussed.
