A Variation of the Speed of Sound Experiment

An experiment which is familiar to most physical chemistry students is the speed of sound based on the Kundts tube.[1] The experiment also allows the student to determine the heat-capacity ratio for various gases. The process of changing gases may be more easily accomplished if the microphone in the tube can be fixed in its position relative to the speaker. In this article, this modification to the experiment is discussed in terms of resonance generated in closed pipes.     

A PC Interface for a Single-Ratio Stepper Motor

A very simple stepper motor controller was designed and built for a scanning monochromator. The circuit design centers around a programmable peripheral interface chip that controls the gate of four power transistors, which in turn activate the coils on the stepper motor. Besides being very inexpensive to build, the interface shows improved performance when compared to the commercially available controller.