By Cassandra Tribe, Updated March 24, 2022
With a handful of readily available components, you can construct a compact permanent‑magnet alternator. This project is ideal for beginners seeking hands‑on experience with electromagnetism and motor theory.
Using a clean coffee‑can lid, trace the rotor’s dimensions onto its center. Place the disc perpendicularly over the rotor, verifying a precise centering. Keep the lid flat on your workspace; do not attach it yet.
Arrange 14 N‑35 neodymium‑iron‑boron magnets around the disc, spacing them evenly and alternating the poles. Apply a small amount of superglue to the disc’s edge where the first magnet will sit, ensuring it lies flush with the rim. Allow the glue to dry. Use shim material—wood, plastic or metal—to build a level surface for the remaining magnets. Adjust shim layers until you can place each subsequent magnet so that its pole repels the one beneath it. Once the spacing is correct, glue the remaining magnets, using a glue accelerator if desired, and confirm the alternating pole sequence.
Secure the magnet‑laden disc to the rotor—either with epoxy or by clamping it with a few high‑strength magnets. Spin the motor briefly to confirm the disc remains firmly attached while the rotor turns.
Mount the motor to a wooden frame or stand so the rotor can spin freely. The frame should accommodate the magnet wheel while keeping surrounding components clear. The assembly may lie flat or stand upright, depending on your workspace.
Using a handheld coil winder, wind two separate coils of approximately 400 turns each from #30 AWG enamel‑coated magnet wire. Leave both ends of the wire exposed, stripping the insulation for future connections, and apply a light coat of superglue to secure the coils in place.
Attach the first coil to a small wooden block and place it on the frame. Ensure the magnet wheel can pass over the coil with a clearance of roughly 1⁄8 inch. Secure the block. Repeat with the second coil, aligning it so that one of the wheel’s magnets is centered directly above it during rotation.
Connect the free ends of the two coils in series by splicing a pair of wires together. Attach the other ends to your load or a multimeter to monitor output voltage. Adjust coil placement as needed to optimize performance.
When attaching magnets, always place the new magnet over the one already glued to ensure repelling poles. This guarantees an alternating pole pattern.
The magnets used in this project are powerful. Handle them with care, as they can snap together quickly, potentially causing pinches or skin injuries.
