Electrical Workshop Handout

10/25/2010FIRST®For Inspiration and Recognition of Science and TechnologyRobotics SubsystemsTeam 358Hauppauge High SchoolElectrical WorkshopOctober 20101• Major Subsystems– Mechanical– Pneumatic– Electrical – SoftwareThis workshop will coverthe Electrical Subsystem2Electrical Subsystem Topics• Presentation– Electrical Theory– Block Diagram and Major Components– Wiring Basics– Safety– Electrical Tools• Hands-On Demonstrations– Wire Stripping and Crimping– Soldering– PWM Motor Speed Control– Parts IdentificationElectrical Theory341

10/25/2010Basic Electrical TheoryThe Water Analogy• Ohm’s LawE = Voltage (Volts)I = Current (Amps)R = Resistance (Ohms)I = E / RP = Power (Watts)P = E * ISymbol: VSymbol: ASymbol: ΩSymbol: WBattery PumpE = Voltage (Volts)I = Current (Amps)R = Resistance (Ohms)+ is the High Pressure Side- is the Low Pressure Side Water Pressure Water Volume Flowrate Flow RestrictionWe use a Positive Current convention(Current flows from + to -)56Resistance RulesElectrical Circuit Example• Resistor Symbol• Series ResistanceR = R1 + R2• Parallel ResistanceR = (R1 * R2) / (R1 + R2)7• What is thecombined resistanceof R1, R2 and R3?• What is the currentbeing supplied bythe battery?• What is the voltageacross R3?• What is the powerdissipated by R3?Kirchhoff's Voltage LawThe sum of voltage sources and voltagedrops in a circuit must equal zero82

10/25/2010Electrical Circuit Challenge• What is the polarityand magnitude ofthe voltage thatwould be measuredbetween points Aand B?Hint: Kirchhoff's Voltage LawThe sum of voltage sourcesand voltage drops in a circuitmust equal zero• Digital SignalDigital vs. Analog– Binary values (0 or 1)– Each value represented by a specific voltage• Analog Signal– Continually variable– Random or waveform (sawtooth, sine, etc)910Robot Electrical Block DiagramElectrical BlockDiagram and MajorComponents11123

10/25/2010Power Source and Power DistributioncRIO ControllercRIO with Interface ModulesAnalog Digital Solenoid12 Volt BatteryLead Acid18 AhPower Distribution Panel12 Volt Power DistributionCircuit Breaker protection24 Volt source5 Volt sourceCircuit BreakerHigh Current (120A)Used to enable anddisable Robot Power13Contains an industrial 400 MHz Freescale MPC5200 processor that supportsthe execution of code on the Wind River VxWorks real-time operating systemInterface Modules can be added or removed depending on the applicationShown with Analog Input, Digital I/O and Solenoid Control ModulesWiring can be via Bumper (blue/red card on Solenoid Module)or Cable & Sidecar Expansion Module14Controller and Digital I/OController and Analog InputcRIOControllercRIOControllerNI-9201 Analog Input(w/Analog Bumper)Analog inputs alsow/standard 3-pinconnectorsNI-9403 Digital I/OInterface to DigitalSidecarNI-9403 Digital SidecarHandles PWMs, DigitalI/O, Relays w/standardInter-connecting3-pin connectorsCable 15164

10/25/2010Controller and Solenoid ControlMotor Speed Controllers and SpikescRIOControllerNI-9472 Relay Controller(w/Pneumatic Bumper)Solenoid outputs directlycontrols pneumaticvalves without spikesJaguar Motor ControllerPWM Motor speed controlBi-directional, variable speed40 Amp load884 Victor Motor ControllerPWM Motor speed controlBi-directional, variable speed40 Amp loadSpike Relay ControllerHigh current power switchingCompressor, Motor ControlOn/Off only40 Amp load1718Pulse Width Modulation (PWM)Analog and Digital SensorsFastMediumSlowExamplesLimit switchesIR sensorsDigital EncodersDigital AccelerometersPWM WaveformsPWM Motor DriveSwitches the motor on and off with a series of pulses of different duty cyclesProvides high torque at low speedsPulses are always 0 to 12 voltsThe polarity can be changed to reverse motor direction19ExamplesPotentiometers (variable resistors)Analog EncodersAnalog Multi-position SwitchesGyroscopes205

10/25/2010Wire CharacteristicsWiring Basics• Basic types– Solid (single wire)– Stranded (multiple smaller wires twisted together)– Jacketed (multiple insulated wires with an outercover)• The size (diameter) of a wire is referred to asthe “gauge” of the wire– The smaller the gauge, the larger the wire– The larger the wire, the lower the resistance per foot– The larger the wire, the more current it can handle– Undersized wire can produce excess heat2122Wire Gauge TableAWG Stranded Wire TableWire Gauge RulesTypical First Robotics Wiring Rules23246

10/25/2010Electrical ToolsWire StrippersElectrical ToolsWire Terminals and Crimping Tools3334Electrical ToolsTie Wrap Gun and Tie WrapsElectrical ToolsSoldering Iron35369

10/25/2010Electrical ToolsDigital Multi-Meter or Digital Volt Meter (DVM)Electrical ToolsClamp-On Current Meter (Amprobe)Measures:VoltageResistanceCurrentContinuityMeasures:Current(AlsoResistance &Voltage withprobes)3738Electrical ToolsOscilloscopeMeasures:VoltageVs.TimeDemonstrations394010

10/25/2010Hands-On Demonstrations• Wire Stripping and Crimping• Soldering• PWM Motor Speed Control• Parts Identification using an existing Robot4111