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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)