## Tuesday, 29 January 2013

### Realise the Dream 2012 Video

In December I helped out at the Realise the Dream competition as a student mentor. I have participated in the great event. Where high school students are chosen from the top projects in science and technology fairs around the country and bought together in a week long trip around New Zealand seeing different research centres and sights. Culminating in the award ceremony at government house.

Also have a look at some of the project one of my personal favourites is a window cleaning robot and a rubik cube solver a student made from scratch without going to the internet!
http://www.realisethedream.org.nz/participant-projects.htm

## Monday, 14 January 2013

### Automatic fish feeder

My fiancĂ©e 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.