What kind of hardware is suitable to monitor eating habits of squirrels?
That's a tough question, a lot of practicable solutions are coming into my mind. Nowadays a wide range of sensors and micro-computer platforms are available to choose from.
Currently a reed switch and a 7-Segment LED display are attached to the Raspberry Pi's GPIOs to monitor the squirrels.
The reed switch's magnet is mounted on the feeder's lid. To give visual feedback how often the lid has been opened the 7-Segment LED display shows the number of openings of a meal break. The IoT Squirrel Feeder starts tweeting after having a mealtime.
I've added a 5$ stand alone ESP8266 based Witty Cloud board to read and publish weather data to ThingSpeak in case the Raspberry Pi based feeder needs some maintenance. A DHT22 sensor is used to read temperatures and humidity.