Physical Computing (Chap 1 & 2) Benjamin Coderch Soto Chapter 1: Electrical Basics Transduction is the conversion of one form of energy into another. Since the base of all this transduction is electrical energy, it is necessary to understand the bases of how electricity works first. Electrons have a tendency to go from one point of greater electrical energy to a point of lesser electrical energy. To flow from one point to another, electrons need a physical medium, called conductor, which allows electrons to flow. A circuit is a closed loop containing a source of energy and a load. Every component into a circuit has certain electrical characteristics, so it is very important to know the theory basis of electronics that is the relationship between Power, Voltage, Current and Resistance (This concept is applied only in DC since AC includes Impedance). This is given by Ohm’s law and complemented by Kirchhoff’s law. Generally speaking, electronic circuits don’t need lots of electrical power since they use power to register data into microprocessors, and turning on small devices such as, diodes and transistors using a direct current (DC) supply. DC power supplies consists in a constant voltage between the source and ground. On the other hand we have other kind of devices uses an alternating current (AC) witch is the commercial electrical power, in other words the kind of power that a TV uses. How Electricity Flows: They are two basic properties: • •
Electricity always flows the path of least resistance to ground. All the electrical energy in a circuit must be used.
Chapter 2: Shopping First come first, you will need to buy some electronic parts and tools. Following is a description of some of the parts you’ll need to get started.
Solderless Breadboard: Also called ProtoBoard, is a tool for holding the components together and connect them together. Microcontrollers: Is the center and “heart” of the circuit. Some of their features are: • They have a programming environment witch allows you to implement programs into the PIC and change the behavior at will. • Analog-to-Digital converters, witch allows you to read analog variables as digital values. • Digital Inputs and Outputs, to control other electronic devices. • Speed of execution and reasonable amounts of memory at low prices. Switches: Are devices that pass or interrupt the flow of electricity. Resistors: Convert electricity into heat. They have a color code that indicates the parameters of each resistor. Variable Resistors: Equal to resistors but they can vary the amount of resistance depending of a factor. Capacitors: This devices stores energy until the current is removed, in this instant, the capacitor releases all the charge in it. Diodes: Since the junction of two semiconductors makes them, they have polarity that means they have different behavior depending on the way you connect them. They are many different types of diodes; the more commonly used are the 1N400X, known as “Rectifier” and the LED’s (Light Emitting Diode). Transistors: Another kind of semiconductors, but with more than two junctions. In their simplest state they’re used as an electronic controlled switch. Other components: • Wires • Power Supply and power connector • Voltage regulator • RC Servomotor • Serial Connector and serial cable • Clock Crystals • Headers • Tools (Soldering Iron, Cutters, Screwdrivers, Multimeter, Hot glue gun)