Development of a Speed and Torque Measurement Test Rig for Small DC Motors Used in Student Research Projects in FCT Abuja

Accurate characterization of small DC motors is essential for engineering students and researchers designing mechatronic systems, yet dedicated motor test equipment is often unavailable in Nigerian university laboratories. This project presents the development of a low-cost speed and torque measurement test rig for small DC motors commonly used in undergraduate and postgraduate research projects in institutions within the Federal Capital Territory. The rig employs a rotary encoder for speed measurement and a load cell coupled to a friction brake assembly for torque measurement. Both sensors are interfaced with an Arduino Mega microcontroller that computes shaft speed in revolutions per minute and shaft torque in Newton-metres, from which mechanical output power is derived. Calibration of the torque measurement system was achieved using certified dead-weight loading on a known moment arm. The test rig was validated against a commercial motor analyser using five DC motors of different ratings, ranging from 12 to 48 volts and 50 to 500 watts. Speed measurement agreement was within 1.5 percent and torque agreement was within 3.2 percent of reference values across all tested motor ratings. A MATLAB interface was written to plot speed-torque and efficiency curves from logged measurement data. Total fabrication cost was approximately 67,000 Naira, representing less than 10 percent of the cost of equivalent imported test equipment. The rig has been adopted for use in the mechatronics laboratory of the African University of Science and Technology in Abuja. Keywords: motor test rig, speed measurement, torque measurement, DC motor, laboratory equipment