3D Relay Model for Classroom Demonstrations

I recently created a 3D CAD model of an automotive relay to help students visualize how a relay functions internally. While physical relays are excellent for hands-on learning, it’s often difficult to see the moving parts and understand how current flow changes when the relay is energized. This model makes it easier to show what’s happening inside.

Why I Built It

When teaching relay operation, one of the biggest challenges is explaining the relationship between the coil and the contacts. Students can measure voltage and current, but the mechanical action that occurs inside the relay is hidden.
By creating a transparent and fully animated model, instructors can demonstrate how the coil creates a magnetic field that moves the internal switch contacts when energized.

This model serves as both a visual and conceptual aid—a bridge between circuit schematics and real-world hardware.

About the Model

The CAD model was designed in Fusion 360 and includes all major components of a standard electromechanical relay:

Coil winding and magnetic core
Movable and stationary contacts
Return spring mechanism
Terminals for coil and switch connections

The parts are fully constrained and can be animated to show how the contacts move when the coil is energized. This makes it a great tool for classroom projection, online demonstrations, or inclusion in training materials.

For Instructors and Students

Educators can use this model to:

Illustrate the difference between the control and load sides of a circuit
Demonstrate normally open (NO) and normally closed (NC) configurations
Discuss back EMF and the importance of diodes across relay coils
Reinforce how relays are used for low-current control of high-current circuits

Whether you’re teaching basic automotive electrical concepts or advanced electronics, this model provides a clear visual reference for relay operation.