Built the following circuit to experiment with basic I/O using a Raspberry Pi
- We're controlling a motor (via transistor/current source) to demonstrate an output device.
- We're monitoring a switch and photo-diode to test a couple different types of possible input.
The circuit is quite basic, but is sufficient for this experiment.
The Python script motorTest.py allows the motor to be started, by pressing the button (SW1), then lets the motor complete 10 revolutions before stopping the motor. A photodiode (D4) is used to detect when the motor completes a full revolution.
We're handling both the switch and the photodiode with the gpiozero Switch class. For the photodiode we had to include some non-default parameters in the constructor to account for the noisy transition between OFF and ON states.
The motor is handled with the gpiozero Motor class. Our circuit doesn't use a H-bridge (we drive the motor with a single GPIO pin) but we're still able to control the motor - including adjusting the speed via PWM. NOTE: The second GPIO pin is required in the initialization of the Motor instance (the reverse pin) but we simply provided an unused GPIO pin. Obviously, we are only able to use the forward() command when controlling the motor.