A Study on the Time Constant Measurement of an RC Circuit Using a Microcontroller

In this paper, a time constant measurement device was developed using a microcontroller with an embedded web server to facilitate measurement control and data collection via the web.In the RC circuit, the voltage change over time during the charging or discharging process was measured and recorded at regular intervals using the internal interrupt of the microcontroller.To test the measurement device, experiments were conducted using two resistors and two capacitors, and two analysis methods were used to determine the time constant.The first method involves calculating the capacitor voltage at five multiples of the time constant and reading the corresponding time to determine the time constant from the time vs. time constant multiple graph.This method aims to help students understand the concept of the time constant more easily.The second method involves calculating the voltage for the charging or discharging time based on the predicted time constant and finding the time constant that minimizes the sum of squared errors between the calculated voltage and the voltage obtained from the experiment.Comparing the sum of squared errors for the two analysis methods shows that the second method is 5 to 17 times smaller, indicating that a very accurate time constant can be obtained.