I'm designing a circuit with the IOIO-OTG board and a vibrating motor. The idea would be to have a digital pin on the IOIO board control the state of the motor (either ON or OFF).
The motor operates from 2.5 to 3.8 volts and the IOIO-OTG ports provide a 3.3 or 5V digital output (up to 5V if you use a drain circuit).
My current understanding is that I should be able to do something like this:
IOIO port @3.3V -> resistor -> motor @3V -> ground on IOIO
However, from what I'm reading, I should use a transistor and have the digital pin connect to its base. I remember from my electrical engineering classes that a BJT can be used as such a switch. However, I have a few questions regarding this:
- What is wrong with my original implementation above? I assume it has to do with the safety of the board.
- Is the proper implementation one with a transistor?
- Are there any best practices I should be observing to protect the motor and the board for my little project?
Whether you need a transistor buffer or not will depend on the current capability of the IOIO-OTG board, and the current requirements of your motor.
A quick look through some of the IOIO_OTG documentation didn't reveal any IO current spec, but a photo of the board just shows one chip - presumably the PIC microcontroller, so I would assume the board can only safely drive a 20 mA load. I would expect any motor to require more than 20 mA so you will almost certainly need a transistor buffer to control it.