SAMI MAKERSPACE MAKE: AN ELECTRONICS WORKSHOP

ELECTRICITY BASICS

IN THIS PRESENTATION: What is electricity? The water analogy. Voltage/Electric Potential Current Resistance Ohm’s Law Electrical Safety Sources of electric potential (batteries, power supplies, Arduinos)

WHAT IS ELECTRICITY?

There are small particles of “charge” called “electrons.” Some elements can pass electrons (conductors) and some cannot (insulators). When electrons move through a conductor, we call it electricity.

WATER ANALOGY

WATER ANALOGY FOR ELECTRICITY When water flows through the plumbing in your house, there are three important things: the water pressure, the rate of flow, and the amount of constrictions in the pipes. Water pressure = Electric potential or “voltage.” Water current = Electric current or “amperage” Constrictions in the pipe = Electrical “resistance”

ELECTRIC POTENTIAL (VOLTAGE)

Defined as the amount of potential energy in the circuit. Symbol: V Units: Volts, or just V for short

Water Tower Water Tower V2 V1

ELECTRIC CURRENT

ELECTRIC CURRENT (AMPERAGE) Defined as the amount of charge that moves through a circuit in a given amount of time. Symbol: I (Capital ‘i’ because of the French word for ‘intensity’) Units: Amps, or just A for short

CURRENT FLOW ANALOGY High CurrentLow Current

RESISTANCE

RESISTANCE (IMPEDANCE) Like it sounds, this describes how much something resists the flow of current. Symbol: R Units: Ohms, or just Ω for short (the Greek letter ‘omega’)

RESISTANCE ANALOGY Big Pipe == Lower ResistanceSmall Pipe == Higher Resistance Water Tower Water Tower V V

OHM’S LAW

This law describes the relationship between the voltage (V), current (I), and resistance (R) of a circuit. Here it is in three algebraically equivalent forms:

ELECTRICAL SAFETY

SAFETY: DAMAGE TO OUR RESOURCES Damage to electrical systems: Overload: too much voltage/current and not enough resistance. Can result when there is a “surge” or electricity. Hence, surge protectors. Short circuit: when there is too little resistance in a circuit. Often the accidental result of insufficient or faulty insulation around conductors. Preventing overloads and short circuits: Use Ohm’s Law to predict the proper values of V, I, and/or R for your circuit before you connect and real power supply. Use insulated wires and components and inspect them for damage before use.

SAFETY: DAMAGE TO YOU! ELECTRICAL SHOCK Important factors: Frequency of current: AC (wall outlet) is much more dangerous than DC (batteries) Amplitude of the current: You can stop your hear with mA of DC current, or only 30 mA of AC current! Path through body: Across your heart and lungs is the worst.

SAFETY Preventing electrical shock: Never work on something that is currently plugged into a wall outlet or that will be plugged in in the future. Remove batteries from objects when working on them. Do not work with 12V lamp batteries, car batteries, power drill batteries, laptop batteries, or anything similar. Always use insulated wires. Carefully inspect circuits before you power them. Be careful of close connections (i.e. solder points on a circuit board)

SOURCES OF ELECTRIC POTENTIAL

Batteries Labeled with their voltage. Connecting in series will add voltages together. Expensive and environmentally taxing. Safer than anything plugged into a wall outlet. Power Supplies Turns alternating current, high voltage electricity from the wall outlet into manageable direct current. Adjustable voltage and current. Expensive if damaged. Potentially dangerous (connected to wall outlet), but have protective fuses. Arduinos (when powered) Have a regulated 5V and 3.3V output. Limited amount of current can be supplied. Ardunios can potentially be damaged ($$$).