A robot may not injure plants, humans or other animals or, through inaction, allow a being to come to harm.
A robot must obey the orders given to it by human beings, except where such orders would conflict with the First Law.
A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.
Our latest prototype, named alpha II, consists of three transparent storage boxes made of polypropylene. The aquaculture resides in a 40x30x30 cm box at the bottom of the vertically stacked system. A submersible heater keeps the roughly 35 Liters of water at the correct temperature. An aerator feeds an air stone inside the aquaculture to ensure the perfect level of dissolved oxygen. A bilge pump is used for water transportation. A watertight led tube is responsible for day and night cycle inside the module. The floor of the box is covered with gravel suited for aquariums that has no apparent erosion changing the PH of the system. A lid covers the box.
The hydroculture sits on top of the aquaculture. The dimensions of the box are 40x30x30 cm. It is equipped with a water-sensor that measures electrical resistance between a total of three contacts. As soon as water touches the contacts, resistance drops and the sensor is able to detect the water-level. A watertight sensor measures the temperature of the grow media and another heater makes sure the roots of the plants feel comfortable. For your being able to see your leafy friends even better, we installed another led tube. The grow bed is filled with inflated clay pebbles with a grain of 8-14 mm.
The top cover of the system is made out of another box. It rests on the hydroculture-box upside down so that the floor is facing upwards. The top case holds a digital temperature and humidity sensor. A light intensity sensor lets your robot decide wheather additional electric lighting is needed or not. If so, a 220 V AC, 60 W full spectrum fluorescent lamp does the job. The aerator that supplies the aquaculture with oxygen is mounted to the top of the cover. This way, the warm air of the hydroculture module is used to heat part of the aquaculture. On the side of the box a 40 mm fan takes care of regulating temperature and humidity. A webcam let's you visit your loved ones anytime.
Water transportation is established by a transparent acrylic pipe, mounted to the side of the box, reaching from the pump in the aquaculture to the top of the growbed. The pipe is flow and return at the same time. Parallel to the water-pipe, all the way from the aerator in the top case to the airstone in the aquaculture, a second pipe handles air transportation. Electric power and data signals are transported by a 24-pin atx cable integrated into each of the three boxes.
Between the boxes, water, air and electric signal lines are connected through sockets, ensuring a fast and easy disassambly of the individual modules.
On top of the system all electronics rest between two lids. For easy accessability, the lids can be flipped open. All actors of the system are connected to relays. Aerator and light are triggered by a 2 channel machine tool relay board and remaining actors are hooked up to an 8 channel machines tool relay board. The relays are capable of switching 240 V alternating current, as well as 40 V direct current, at up to 10 A with a 3-5 V direct current input on the coils. For safety reasons, switching and coil current are separated by an opto-coupler.
The relay boards and most of the actors are powered by a micro-atx power supply unit mounted to the side of the upmost box. The PSU is short-circuited in order to run without a computer mainboard.
An Arduino acts as the nervous-system of the robot, connecting the sensors and switching all actors regarding to decision trees. All sensor measurements, actor states and other meta data is transmitted to a raspberryPi via serial connection, in the form of JSON.
A credit-card-sized, open source computer called raspberryPi that features an ARM processor running at 1 GHz and with 512 MB RAM serves as the brain of the robot. The operating system used is an ARM ported version of Debian Wheezy, a Linux based system. Brain functions are established by nodejs. A mongoDB holds all the robots' lovely memories of its human, green and wet friends. The interface, based on twitter bootstrap ensures communication with the robot from anywhere, at any time and with any webbrowser. The robot supports WIFI for an easy integration into any home-network.
An USB-hub lets you connect even more gadgets to your system.