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Basic Electronics Review B. Furman 27JAN2015

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Lecture Flow Today Items to focus on this week Lab 1 PortMaster build HW 1 and Questionnaire due Thursday Term Project overview + video of past projects Finish basic electronics review: Voltage divider Impedance of a capacitor

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Learning Objectives Get prepared for Lab 1 and started on PortMaster build Get started on the term project Explain in simple terms what is meant by: Voltage Current Ground Resistor, Capacitor, Inductor Impedance Power Determine equivalent series and parallel impedances Explain the significance of a voltage divider Derive an expression for the impedance of a capacitor

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Mechatronics Concept Map System to Control Sensor Signal Conditioning Controller (Hardware & Software) Power Interface Actuator User Interface Power Source BJ Furman 22JAN11 ME 106 ME 154 ME 157 ME 195 ME 120 ME 297A ME 106 ME 120 ME 106 ME 190 ME 187 ME 110 ME 136 ME 154 ME 157 ME 182 ME 189 ME 195 ME 106 ME 120 ME 106 INTEGRATION

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Lab 1 – Intro to the Mechatronics Lab Read and prepare Take the pre-lab quiz

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PortMaster Solder practice Bit manipulation and port IO learning

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HW 1 and Questionnaire When are they due? Hard and softcopy

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Term Project Overview Video sample of previous projects

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Key Concepts Voltage Ground Current Resistor Capacitor Inductor Impedance Power Take out a sheet of paper Explain the concepts in terms that a 6 th grader could understand First, work on your own, then, introduce yourself to someone you have NOT met yet, and share your answers.

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Basic Electronics Review - 1 Voltage – put it in terms that a 6 th grader could understand “Pressure” Pressure on electric charge (e - ). Units are in Volts Urges charge to ‘flow’ Measured relative to a reference pressure level An “across” quantity – we measure it across two points (Don’t say ‘the voltage through…’) R1 R2 R3 ViVi + A B C D “High” pressure “Low” pressure Voltage source acts like a pump Ground is often taken as the low pressure point, but any point could be taken as ‘ground’ ex. V AD = V i = -V DA

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Basic Electronics Review - 2 Current – put it in terms that a 6 th grader could understand “Flow” Flow of electric charge (e - ). Units are in Amps The response of charge to applied voltage Need a complete circuit for current to flow A “through” quantity – we measure it through an element R1 R2 R3 ViVi + A B C D “High” pressure “Low” pressure We will assume ‘conventional’ current flow – positive charges flow out of the + terminal and return to the - terminal I

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Basic Electronics Review - 3 Resistor – put it in terms that a 6 th grader could understand “Flow restriction” (causes a pressure (voltage) drop across it), an impedance Drinking a milkshake through a straw Small diameter straw – high resistance Causes large pressure drop Large diameter straw – low resistance Causes small pressure drop Units are in Ohms Dissipates power in heat! R1 R2 R3 ViVi + A B C D “High” pressure “Low” pressure

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Basic Electronics Review - 4 Ohm’s Law (know it cold!) V=I*R A relationship between current and voltage for a resistor The slope of the V-I line The voltage drop across a resistor is proportional to the current through it V, volts I, Amps R R increasing V IR

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Basic Electronics Review - 5 R1 ViVi + A D R3 R2 ViVi + R eq A D Original CircuitEquivalent Circuit

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Basic Electronics Review - 6 Power (units are in Watts) P = I 2 R = (V/R) 2 R = V 2 /R P = I 2 R = I 2 (V/I) = IV Note: can calculate the power required for any circuit by measuring I and V and taking their product R1 R2 R3 ViVi + A B C D Any circuit I

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Capacitor Capacitor– put it in terms that a 6 th grader could understand “Accumulator”, water tank Pressure storage. Stores energy in an electric field Voltage across the leads takes time to build up. Units of capacitance are Farads +- V

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Inductor Inductor – put it in terms that a 6 th grader could understand “Flywheel, merry-go-round” An inertia. Stores energy in a magnetic field Tries to oppose changes in current flow. Units of inductance are Henrys +- i V

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The Voltage Divider Consider two resistances in series What is V A in terms of V i, R1 and R2 ViVi + A D R2 R1 VAVA

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So what? Why is this important? Voltage divider effect occurs whenever one circuit is connected to another Voltage dividers can be used to set a voltage level somewhere between a given supply voltage and ground If significant current is desired, it is better to use a power supply or voltage regulator

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