Laboratory of Sensors Engineering Sciences 9 CFU

Laboratory of Sensors Engineering Sciences 9 CFU

Contacts Alexandro Catini catini@ing.uniroma2.it Phone: +39 06 7259 7347 Department of Electronic Engineering First Floor - Room B1-07b

Course Outline THEORY (Monday): Introduction to sensors Circuits for resistive and capacitive sensors Temperature sensors: thermistors, thermoelectric effects Magnetic field sensors; Optical sensors Photoconductors and Photodiodes; IR sensors Mechanical sensors: position, strain gauges, accelerometers, gyroscope, pressure sensors, flow meters, micro electro mechanical systems Design of sensors applications Use of sensors data analysis software LABORATORY (Friday): Intro to physical computing, electricity and electronics, sensor components, examples of work, intro to the fast prototyping boards Using the breadboard to build simple circuits, Digital input and output, build sensor interface Analogue Input and Output, MATLAB Hacking everyday objects, building more complex circuits, interfacing with processing

Lecture slides and information http://didattica.uniroma2.it/home/ Exams Reports after each laboratory experience Final project Oral questions

Class skills and Instrumentation HARDWARE: Sensors, Actuators, Passive and Active Components Arduino / Raspberry PI Notebook Digital Multimeter Power Supply SOFTWARE: Arduino IDE MATLAB

Physical Computing Physical computing is about creating a conversation between the physical world and the virtual world of the computer. The process of transduction or the conversion of one form of energy into another is what enables this flow.

Pervasive Computing

What is Interaction? Interaction is an iterative process of listening, thinking and communicating between two or more actors. Input Output Processing Transduction/Understanding

Electronics

Microcontrollers

Wireless Sensor Networks

Introduction to Electricity Electricity is the flow of tiny charged particles called electrons. Electrons are present in all substances, but in some materials they are not free to move. These substances are known as insulators. Substances which permit the flow of electricity are called conductors.

To best describe how electricity and electric circuits work, we use what is called the Water Analogy

Water flowing = electrical Current (amps) Water Pressure = Voltage (volts) Size of Pipe = Level of Resistance (ohms)

Power and Ground Connections All electrical and electronic devices exploit the fact that electrons have a tendency to go from a point of greater electrical energy to a point of lesser electrical energy. You provide a positive connection (greater energy or power) A negative connection (lower energy, or ground) A conductor through which the electrons flow.

Circuits A circuit is a closed loop containing a source of electrical energy (i.e. a battery) and a load (i.e. a light bulb)

Electricity Vs. Electronics Electronics is a subset of electrical circuits used to convey information.

Sensor Technology One of the main principles behind physical computing is transduction, or the conversion of one from of energy into another A microphone is a classic transducer because it changes sound pressure into electrical voltage.

Sensors and Actuators Input transducers (sensors) such as switches and variable resistors, convert heat, light, motion and sound into electrical energy. Output transducers (actuators) such as motors and buzzers, convert electrical energy into the various forms of energy the body can sense.

Common Components in Sensor Technology There are two different types of sensors: Digital and Analogue. Digital = on/off or zero/one Analogue = Any range of values, a continuous line

Switches Switches pass or interrupt the flow of electricity A simple switch has two interchangeable leads. The leads are attached to two contacts inside the switch that can put them in contact with each other or be separated by the actions of the switch.

Fixed Resistors Resistors give electricity something - they convert electrical energy into heat. Resistors are rated in ohms, indicating how much resistance they offer a circuit, and in watts, indicating the max power they can take.

The value of a resistor will be written right next to its schematic symbol

Resistors

Variable Resistors These are very common transducers for analogue input. Thermoresistors Photocells or Photoresistors Force sensitive Resistors Flex Sensors Potentiometer

Thermoresistors convert a change in heat to a change in resistance. Photocells or Photoresistors change their resistance in response to changing light levels

Force sensitive resistors respond to a changing force exerted on them. These are often used in pressure sensors

Flex sensors change their resistance when they are bent at varying angles: they re often used in interactive gloves

Potentiometer: The most common of all variable resistors is called a potentiometer or pot and this is what is behind every volume knob.

Capacitor: These store electricity to be released at a later point They are rated by how much charge they store, which is called their capacitance measured in farads F.

Diodes: A diode only allows electricity to flow in one direction and not the other. An LED is a light emitting diode that emits light in the process. The shorter leg is the cathode (negative), the longer LED is the anode (positive).

Switching Devices: Transistors and Relays Transistors and relays are switching devices. Normal switches can be thrown by your finger, but these can be thrown by an electronic signal from your microcontroller.

Wires

Solderless Breadboard A breadboard is a tool for holding the components of your circuit, and connecting them together. It s got holes that are a good size for wires and the ends of most components, so you can push wires and components in and pull them out without much trouble.

Arduino Arduino is an open source physical computing platform based on a simple input/output (I/O) board and a development language that implements the processing language (www.processing.org) Arduino can be used to develop standalone interactive objects of connected to software on your computer, such as flash, Processing, VVVV or MAX/MSP The boards can be assembled by hand or purchased preassembled; the IDE (integrated Development Environment) can be downloaded for free at www.arduino.cc

Introduction to Arduino Arduino is a multiplatform environment; it can run on Windows, Macintosh and Linux. It is based on the Processing programming IDE, an easy to use development environment used by artists and designers. You program it via a USB cable. It is open source hardware and software There is an active community of users so there are plenty of people who can help you.

The Arduino Platform Arduino is composed of two major parts: The Arduino board; which is the piece of hardware you work on when you build your objects; The Arduino IDE, the piece of software you run on your computer. You use the IDE to create a sketch ( a little computer program) that you upload to the board. The sketch tells the board what to do.

The Arduino Hardware The Arduino board is a small microcontroller board, which is a small circuit (the board) that contains a whole computer on a small chip (the microcontroller). The board can be powered from your computer s USB port, most USB chargers, or an AC adapter (9 volts recommended, 2.1mm barrel tip, centre positive)

Arduino Hardware 14 Digital IO pins (pins 0-13) : these can be inputs or outputs, which is specified by the sketch you create in the IDE. 6 Analogue In Pins (pins 0-5) These dedicated analogue inputs take analogue values (i.e. Voltage readings from a sensor) and convert them to a number between 0 and 1023. 6 Analogue Out pins (pins 3, 5, 6, 9, 10 and 11) These are actually six of the digital pins that can be reprogrammed for analogue output using the sketch you create in the IDE.