DIY DC Motor Tutorial: Build a Simple Commutator Motor and Learn How It Works

The video demonstrates building a simple DC motor and explains how the coil, commutator, and magnets interact to produce rotation. It covers winding the rotor with enamelled copper wire, crafting the two commutator plates from copper tubing, testing electrical continuity with a multimeter, and assembling the shaft, bearings, and magnet stator. Fleming's left-hand rule is introduced to predict the direction of motion. The demonstration also shows how varying the applied voltage affects speed and discusses practical considerations such as sparking at the commutator and potential improvements for the design.

Introduction and context

Direct current motors convert electrical energy into rotational motion by leveraging interactions between magnetic fields and electric currents. The video outlines a compact, hands-on implementation that uses a fixed magnet assembly (the stator) and a rotating coil (the rotor) mounted on a shaft. A split metal contact known as a commutator provides the path for current to enter and leave the coil while the rotor spins. The core idea is to create torque through the magnetic interaction between the rotor field and the permanent magnets in the stator, a concept governed by basic electromagnetism and the way current directions influence magnetic polarity.

Core parts of the design

The motor design comprises a base to hold everything together, a stationary stator with magnets, supports containing bearings for the rotor and shaft, and a rotor with a wire coil attached to a shaft. The coil ends connect to two copper plates that form the commutator. Wires lightly touch these plates to supply current. The rotor is constrained by bearings to allow smooth rotation, enabling simple further use such as attaching gears or fans.

Electrical operation and magnetic interactions

When power is applied, current travels up one rotor wire into a commutator plate, passes through the coil, and returns via the other rotor wire to the opposite commutator plate. The result is a magnetic field around the coil that interacts with the permanent magnets on the stator. Like magnetic poles repel and opposite poles attract, producing torque that drives rotation. The video also emphasizes that reversing current reverses the coil’s magnetic polarity, which would flip the direction of rotation if not interrupted by the commutator.

The commutator and reversing current

A key feature is the commutator, which reverses current direction every half turn, allowing continuous rotation rather than the rotor aligning with a fixed magnetic field. By flipping the current, the rotor avoids getting stuck at a stable orientation and continues spinning. The explanation is reinforced with Fleming's left hand rule, which relates the direction of conventional current, magnetic field, and motor movement to predict the rotor’s motion.

Winding the rotor coil

The rotor coil is wound with enamel-coated copper wire, typically around 0.22 mm in diameter. The enamel isolates adjacent turns so current can flow through the entire coil, strengthening the magnetic field. The video demonstrates tying the wire through the rotor hole, winding in the clockwise direction, and using 400–600 turns (600 turns in this design). After winding, the ends are knotted through the opposite side and secured to ensure reliable current flow through the coil.

Commutator plates fabrication and assembly

The commutator plates are fashioned from copper tubing cut into short sections, drilled through near one end, and split along the length to create two plates. The ends of the rotor wires are stripped of enamel and connected to each plate, forming a two-terminal commutator that sandwiches the coil. Proper cleaning of the copper surfaces improves electrical contact. The rotor and commutator plates are then aligned so the plates attach to the nearest coil side, keeping the assembly compact and balanced.

Testing and integration

Continuity checks with a multimeter ensure the coil provides a conductive path between the two commutator plates through the coil. The rotor assembly is then placed over a shaft and mounted on a base made from plywood. Bearings are used to reduce friction and prevent lateral movement, while the stator magnets are positioned so their poles face inward as described. A light touch wire on the commutator arms makes light contact with the plates without shorting against other parts. Finally, a bench power supply delivers current to the motor, allowing speed to be varied with voltage.

Performance, limitations, and improvements

With a 12 V DC supply, the motor spins and speed increases with voltage. The design demonstrates the basic mechanics clearly, but the author notes the motor is not high power and can produce sparking at the commutator, which can wear surfaces over time. Several improvements are possible, such as optimizing winding turns, improving bearing quality, using higher performance magnets, reducing sparking through better commutation, or experimenting with coil geometry and mounting to reduce friction and vibration.

Learning resources and next steps

The video references related topics such as DC motors, AC motors, and stepper motors discussed in previous episodes. Viewers can access design files and CAD models for manufacturing parts and consider 3D printing the components for a polished result. This project demonstrates core electromechanical principles and offers a practical entry point to hands-on motor design and experimentation.

Conclusion

By walking through component selection, winding practices, commutator construction, and assembly, the video provides a comprehensive introduction to building a functional DC motor and understanding how the interplay of current and magnetic fields drives rotation. It also invites further experimentation and discussion on potential improvements and alternative configurations.