Vibration motor

A 10 mm coin vibration motor, the disc inside every phone and game pad.

It is a tiny DC motor with an off-center weight on its shaft, so the whole disc shakes at the rate it turns.

Pins

Pin	What it does
1	Red lead.
2	Blue lead. It runs either way around.

Properties

voltage: rated voltage, 3 V. rpm: speed at that voltage, 12000. resistance: winding resistance, 35 ohms. back_emf: the fraction of the supply the spinning motor gives back, 0.125. start: the least voltage that starts it from rest, 2.3 V. inertia: how quickly it spins up, 40 ms.

What the model gets right

It is the DC motor model with a coin motor's numbers, and the numbers are the lesson. The weight and the tiny bearings take nearly all the torque, so it runs at almost its stall current: about 75 mA running against 85 mA stalled. That is four times what a board pin should give, so it goes on a transistor like any other motor. And it has to be started: under 2.3 V a stopped motor does not turn at all, though a turning one keeps going down to about two thirds of that. A PWM duty too low to start it is the first thing a haptics sketch gets wrong.

The probe is the speed in rpm; the part shows the shaking in hertz, the speed over sixty, which is 200 Hz at 3 V.

What it does not model

Inductance, so the diode across it is there for the bench rather than for the simulator. How hard it shakes (about 1 g at its rated voltage, rising with the square of the speed), and anything it is glued to.

See it in action

Music box buzzes one on the beat through a transistor. Open it at /templates.