RFID pet feeder

Step 3 Add open/close sensors (pushbuttons)

To ensure that Arduino stops turning the motor when an open/close action has been performed, I mounted two pushbuttons in the tray, which get pressed when the door is all the way open/closed. This also helps to keep track of what state the system is in at all times. I have mounted a metal strip on the tray in such a way that when the door is all the way open, the strip pushes on one button, and when it is all the way closed, it pushes the other button.

Put the Adafruit Motorshield on top of the Arduino. Connect the motor to the motor shield. I use m3 (digital pin 5). Connect pushbuttons to Arduino analog channel 0 and 1 (in Arduino code pin 14 and 15). Add a 10K resistor between each button and ground as a pull down resistor (http://www.ladyada.net/learn/arduino/lesson5.html) and a low one (100-220 ohm) between the button and the analog channel just so the resistance is not infinitely small. The button that is actuated when the tray is extended (i.e. door closed) should be on channel 1 and the button actuated when the tray is retracted (door open) should be on channel 0.

More info about the motor shield: http://www.ladyada.net/make/mshield/faq.html.

You can test the mechanism with a bit of Arduino code that is downloadable here:
http://www.writtensound.com/arduino/cat_feeder.htm