Introduction 2 Electrical Design As you have seen during the first SIK workshop and Simon Tilts workshop, the world of electrical design is complex and detailed. There are many aspects that we will not be covering in this course, but there are several that we must understand in order to build simple circuits that will be involved in our design work. Today, we will formally review these concepts but most of your electrical design work will occur throughout your design projects. Hands-on learning!

What is electrical design? Electronics are ubiquitous today. Almost every device includes at least a simple electronic circuit. The light switch in a flashlight The timing of traffic lights The touchscreen interface in smart phones Electrical designs integrate electrical components into circuit in order to perform a task Include passive components (resistors, capacitors, etc.) as well as active components (diodes, transistors, etc.) Circuits include a power source, input devices, and output devices in order to perform a task. Electronic designs are all around us. Instead of naming all the different circuits we interact with daily, lets think of any device that doesn’t have a circuit. What are some purely mechanical or structural devices? Bikes (without speedometer) Roads (without traffic light sensors) Others? Electrical designs integrate electrical components into a circuit in order to perform a task. Simple passive components are used as tools in order to build the circuit. Power sources, input and output devices integrate the circuit into the real world and allow for interaction.

Key definitions Voltage – a potential difference that creates a electromotive force (measured in volts, V) Water analogy: a water reservoir Current – the electrical charge that passes through a conductor area per unit time (measured in amperes, A) Water analogy: the flow of water in a pipe Ground – the zero voltage reference point within a circuit Water analogy: the bottom of the reservoir Key electrical definitions include voltage, current, and ground. With a sound understanding of these concepts then electical designs can be accomplished. Voltage is the potential difference that creates a electromotive force. It’s like a water reservoir that produces water pressure. We measure it in volts (V) using a multimeter like we did previously. Current is the electrical charge that passes through a conductor per unit time. It’s like the flow of water in a pipe. We measure it in amperes (A). A voltage is necessary to cause a current to flow. Quiz! What is the current in a lamp when you unplug the cord? Why? Ground is the zero reference point within a circuit. It’s like the bottom of the water reservoir since the bottom provide a place to measure the heigh of the water in the reservoir. Also, it’s like a coordinate system in mathematics. Ground provides a reference frame for electrical circuits. Scherz, Paul Practical Electronics for Inventors, McGraw –Hill 2007

Components Battery Resistor Diode Sensor - We’ll review a several important components in the electrical circuits that we will be building this semester. There are many many electrical components that we will not discuss but you might run across in your design projects. Hopefully, this overview will provide a brief introduction.

Components Definition: a type of portable power supply that maintains a constant voltage across its terminals Objective: Supplies power to portable electronic circuits All different types Alkaline Lithium-ion Rechargeable Water Analogy: a pump in a circuit of pipes Battery - We will be using batteries to provide a portable power source. Batteries maintain a constant voltage across its terminals. There are many types of batteries each with their own properties. In general, the battery is like the pump in a circuit of water pipes. It provides power to the circuit and allows for current flow.

Components Definition: any material that controls the current flow due to a certain voltage Purpose: produces a voltage drop within a circuit and can be arranged into sensing elements Resistance affected by Length of material Cross-sectional area of material Resistivity of material Ohmic property Water analogy: a bend in a pipe Resistor - A resistor is any material that controls the current flow due to a certain voltage. It’s properties are defined by Ohm’s law which we will refer to shortly. Resistors produce a voltage drop within a circuit and can be arranged into sensing elements. The inherent resistance of a material is due to many properties including the length, cross-sectional area, resistivity, and ohmic properties. Resistors are components with specific resistivity and are used in most circuits.

Components Definition: A component that allows current flow in one direction and not the other Purpose: An electric gate LEDS – light emiting diodes emit light when current flows in proper direction Water analogy: spring loaded gate in a pipe Diode - Diodes allow for current flow in one direction and not the other. They are basically an electronic gate and are used to protect sensitive electronical components, etc. LEDs produce light when current flows in the proper direction and are used throughout the circuits we will be building. Diodes are like spring loaded gates in a water pipe.

Components Definition: An input device that converts a measurement into a voltage Purpose: Enables interaction between the world and the circuit Many, many different sensors Photo resistor (light) Temperature sensor (temperature) Push button (force) Flex sensor (bend) Soft potentiometer (motion) Potentiometer (rotation) Sensor - A sensor is any input device that converts a measurement into a voltage. Sensors enable interaction between the world and the circuit. Of course, there are too many sensors to list here. Our SIK has many including the photo resistor, temperature sensor, push button, flex sensor, soft potentiometer, and potentiometer. All convert a certain measurement (light, temperature, etc.) into a voltage which is sent into a circuit.

where R = resistance (ohms) Ohms Law The ratio of the applied voltage to the resultant current is defined as resistance by Ohm’s Law R = V / I where R = resistance (ohms) V = voltage (Volts) I = current (Amps) Used to understand voltages, currents within a circuit Necessary to design proper electrical circuits - Finally, Ohm’s law is the most basic electrical circuit principal. Ohm’s law says that the ratio of the applied voltage to the resultant current is defined as resistance. R = V/I or more commonly V=IR. This law allows us to understand the voltage and current within a circuit and thereby design electrical circuits that work properly. Many components require a certain voltage, current, etc. in order to work properly and therefore we will be using Ohm’s law in order to determine local voltages, currents, in our circuits.

The Arduino The Arduino is the open-source brain that will fuel our design projects Watch this TED talk from the founder of Arduino, Massimo Banzi, about how the Arduino platform allows all of your ideas to come true Our electrical circuits will interface with the Arduino platform in order to give ‘intelligence’ to the circuit. The Arduino is an open source microprocessing platform with an entire community of followers who provided code, projects, etc. Let’s get some ideas for Arduino powered projects! Ted Talk here: http://www.ted.com/talks/massimo_banzi_how_arduino_is_open_sourcing_imagination

Open Ideas Catalogue different sensors/actuators in SIK Reverse engineer how each component works Extend the water analogy to other electrical components Use the SIK components as a starting point - Use these open ideas to fill out the period with an interactive team based activity.