· Load is defined as the output of a circuit connected to the device. In motor selection, load can be defined as the torque needed to operate the whole system. The magnitude of load can be a constant, or it can be varied by time.
· Power: Power is the product of speed and torque. The maximum power of a DC vibration motor is produced at the operating point that is defined by operation at half the no-load speed and half the stall torque.
· Torque: The relationship between torque and speed is called a characteristic of the operating system. This DC vibration motor's characteristic varies based on three different magnetization sources: separately excited field, self-excited field or permanent field, which is used selectively to control the motor over the mechanical load's range. Beside these requirements, some restrictions exist as well that limit the motor selection. The major constraint on motor operation is thermal in nature. The heat a motor must dissipate can always be calculated as follows: Pdis = I^2 x R Heat dissipated= current through the motor squared, multiplied by the terminal resistance. The current through a motor is determined by the torque the motor produces. Current and torque are related by the torque constant of the motor: I = Mo / kM Current through motor = torque produced divided by the torque constant.
This application note detailed on introducing the function of electric components in DC motors. After that, bar-type and coin type vibration motor were introduced, and their working theory were described. The reasons why users can feel vibration through using applications of these two motor were discussed as well. In the end, requirements and restrictions about motor selecting were discussed.