Vibration motors

[sdo]

Hi,

I'd like to setup an array of vibration motors, 5 or 6 of them,
controlled from an arduino. And ideally I'd like PWM control over
each. So far I've setup one vibration motor to try out. It works, but
I have a bunch of questions, please.

These are the Vibrating Mini Motor Discs from Adafruit. I first
experimented and drove the motor straight off of an arduino pin, and
that appeared to work fine. I then drove it through an IRLB8721
mosfet. It feels like the motor may be vibrating a bit more when I
feed power from my breadboard's power rail through the mosfet rather
than through the arduino pin, presumably it's able to draw more
current?

I'm assuming that powering 6 vibration motors off of arduino pins
might be asking for a lot of current through the arduino, right? But a
mosfet is perhaps overkill for such a tiny motor? Well that's what I
had on hand. Will it make any practical difference if I use PN2222
instead, does the mosfet have any advantage?

Do I need a flyback diode for a vibration motor?

And a mosfet question: is it helpful/necessary to add a resistor
between the arduino pin and the mosfet gate?

Finally, what might be good ways to control 6 such motors using fewer
than 6 pins?

Many thanks!

[adafruit_support_bill]

A MOSFET or BJT (such as the PN2222) will be able to deliver more current to the motor - and put less stress on your Arduino. The IRLB8721 needs no resistor on the gate. A Pn2222 will require one to limit the base current. Although the MOSFET is overkill, it is more efficient than a BJT and requires fewer parts.

Finally, what might be good ways to control 6 such motors using fewer
than 6 pins?

You can use one of these: The i2c bus requires only 2 pins, and these can be shared with other i2c devices.
https://www.adafruit.com/product/815

[sdo]

Awesome! That's what I wanted to know.

And a flyback diode for a vibrating mini motor discs, is that overkill, prudent, or necessary?

Actually for motor setups in general, can I verify that a flyback diode is working, can I measure its effect, test it? I have one on my breadboard, but its effect is pretty invisible. Is some kind of voltage/current spike visible on a voltmeter when stopping a bigger motor?

Thanks!

[adafruit_support_bill]

And a flyback diode for a vibrating mini motor discs, is that overkill, prudent, or necessary?

For a motor of that size, it is probably somewhere between overkill and prudent. When you stop applying power to the motor, inertia will keep the motor spinning for a while. During that time, the motor is acting like a generator and will put a reverse voltage out on the wires. Vibrator motors don't have a lot of mass, so the effect is short-lived and not so powerful. It is probably too quick to catch with a multimeter. You would need an oscilloscope to see it.