How Does Coin Vibration Motor Work?

These small and compact coin vibration motors are commonly found in smartphones, fitness trackers and other portable electronic devices.

Our coin or pancake vibration motors are designed as eccentric rotating mass (ERM) motors, so they can be operated using the same methods as pager motors. They use the same motor drive principle, including the use of an H-bridge circuit for active braking.

The construction of the brushed coin vibration motor involves a flat PCB on which a 3-pole commutation circuit is arranged around a centrally located inner shaft. The rotor of the vibration motor consists of two "voice coils" and a small mass integrated in a flat plastic disk with a bearing in the center, which is located on the shaft. Two brushes on the underside of the plastic disc come into contact with the PCB commutation pads and supply power to the voice coil, creating a magnetic field. This magnetic field interacts with the magnetic flux generated by a disc magnet attached to the motor's chassis.

The commutation circuit alternates the direction of the field through the voice coils, and this interacts with the N-S pole pairs that are built into the neodymium magnet. The disc rotates and, due to the built-in off-centred eccentric mass, the motor vibrates!