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1.1.2 Investigating Basic CircuitsEquipment and Tools

➢ Components-devices connected in a circuit➢ Breadboard-reusable platform for prototyping temporary circuits➢ Digital Multimeter (DMM) measures current, voltage, and resistance

Breadboards➢ AKA protoboard➢ advanced ones have digital components & programing abilities➢ How it works:

○ leads and wires are inserted into holes arranged in a grid pattern on the breadboard surface

○ internal metal strips serve as jumper wires connecting specific rows○ Printed Circuit Boards (PCB)○ connect electronic components using conductive pathways etched from copper

sheets laminated on a non-conductive substrate○ components attached through soldering

➢ Why Breadboard?○ cheaper & more time efficient that PCB○ allows designer to see if circuit will function○ ability to quickly change components during development & testing○ easy modifications to facilitate measurements of voltage, current, or resistance

➢ Guidelines & Tips○ use as few wires as possible○ keep wires as short as possible○ breadboard as close as possible to the schematic to make troubleshooting easier○ place IC chips in the middle○ check off components from the schematic as they are implemented○ cut component leads to manageable length○ have someone check your circuit for errors

Digital Multimeters (DMM)➢ measure Voltage, Current, & Resistance➢ Data Acquisition Modules (DAQs) turn computers into

useful tools that were typically different pieces of equipments

➢ Proper Use:○ placing leads improperly can cause damage to

the DMM and give incorrect readings

Circuit Diagrams➢ each component has a symbol➢ help circuit designers figure out characteristics of the circuit

➢ Symbols:

Current, Voltage, & Resistance➢ Current (I):

○ the flow of electrical charge through an electronic circuit○ direction is opposite to the direction of electron flow○ measured in amperes (amps)

■ Andre Ampere (1775-1836): French Physicist➢ Voltage (V):

○ electrical force that causes current to flow○ measured in volts

■ Alessandro Volta (1745-1827): Italian Physicist➢ Resistance (R):

○ measure of opposition to flow○ measured in ohms

■ Georg Simon Ohm (1789-1854): German Physicist

Capacitors➢ electronic component that can be used to store an electrical charge

○ “temporary battery”

Battery➢ device that converts chemical energy into

electrical energy○ chemical reaction provides more charge for a

longer time than a capacitor➢ one side of the battery has the potential to do work

(12V-right side)➢ one side of the battery has no potential to do work

(0V-left side)

What is Voltage?➢ in order for a charge to move, there must be a separation of charge or a potential

difference across two points in a circuit➢ voltage is defined mathematically as: ΔV = Vfinal - Vinitial

➢ a Volt (V) is a Joule (J) of work per Coulomb (C) of charge [1V = 1J/1C]➢ a 12 Volt battery is able to do 12 Joules of work for every 1 Coulomb of charge that

battery can provide

Water Tank Analogy➢ Force: the difference in the water

levels = Voltage➢ Flow: the flow of water between the

tanks = Current➢ Opposition: the valve that limits the

amount of water = Resistance

Flashlight

Current Flow➢ Conventional Current

○ assumes current flows out of the positive side to the negative○ convention established when electricity was first discovered, but it incorrect○ used in engineering disciplines

➢ Electron Flow○ what actually happens○ electrons flow out of the negative side of the battery to the positive○ used in science disciplines

Ohm’s Law➢ defines relationship between voltage, current and resistance➢ current in a resistor varies in direct proportion to the voltage applied to it and is inversely

proportional to the resistor’s value○ I = V/R

Circuit Configuration➢ Series Circuit

○ components are end-to-end○ only a single path or current to flow

➢ Parallel Circuit○ both ends of the components are connected together○ there are multiple paths for currents to flow

Series Circuit➢ current flowing through every series component is equal➢ total resistance (RT) is equal to the sum of all of all the resistances (R1 + R2 + R3)➢ the sum of all of the voltage drops (VR1 + VR2 + VR3) is equal to the total applied voltage

(VT)○ this is called Kirchhoff’s Voltage Law (KVL)

Parallel Circuit➢ voltage across every parallel is equal➢ total resistance (RT) is equal to the reciprocal of the sum of the reciprocal

○ [(R1)-1 + (R2)-1 + (R3)-1]-1 = RT

➢ the sum of all of the currents in each branch (IR1 + IR2 + IR3) is equal to the total current (IT)

○ this is called Kirchhoff’s Current Law (KCL)