Automatic fish feeder

My fiancée was asked to look after some fish over the holiday break. However we wanted to go to the beach to celebrate New Years so I quickly put together a fish feeder controlled by an Arduino. It only needed to feed the fish once or twice so I made a small rotor from cardboard which the stepper motor could turn and drop the food into the fish tank.

Unipolar 48 step stepper motor with rotor capable of three dispenses

The stepper motor was driven by four transistors with 2k2 resistors from the Arduino to the base of the transistor and 2k2 resistors from the motor to the transistor to limit the current. 

The design came from Azega blog:

http://www.azega.com/controlling-a-stepper-motor-with-an-arduino/

http://www.azega.com/controlling-a-stepper-motor-with-an-arduino-part-2/

Design of the circuit from Azega

Arduino has a library for stepper motors and it is very easy to use. You specify a speed and the number of steps your motor has. Then you can call a function that will step through as many steps as you require.

Arduino notes on unipolar stepper motors:

http://arduino.cc/en/Reference/StepperUnipolarCircuit

However, I forgot that the delay function used milliseconds not seconds and so the fish were feed a week's worth of food in a few minutes.

So I reached for the slow release fish food instead and vowed to make a better fish feeder next year.