Basic Electronics Review

B. Furman

27JAN2015

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

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

Mechatronics Concept Map

System toControl

Sensor

SignalConditioning

Controller(Hardware & Software)

PowerInterface

Actuator

UserInterface

PowerSource

BJ Furman 22JAN11

ME 106ME 154ME 157ME 195

ME 120ME 297A

ME 106ME 120

ME 106ME 190ME 187

ME 110ME 136ME 154ME 157

ME 182ME 189ME 195

ME 106ME 120

ME 106

INTEGRATION

Lab 1 – Intro to the Mechatronics Lab

Read and prepare

Take the pre-lab quiz

PortMaster

Solder practice Bit manipulation

and port IO learning

HW 1 and Questionnaire

When are they due? Hard and softcopy

Term Project Overview

Video sample of previous projects

Key Concepts

Voltage Ground Current Resistor Capacitor Inductor Impedance Power

Take out a sheet of paper Explain the concepts in

terms that a 6th grader could understand

First, work on your own, then, introduce yourself to someone you have NOT met yet, and share your answers.

Basic Electronics Review - 1 Voltage – put it in terms that a 6th 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

Vi

+

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. VAD = Vi = -VDA

Basic Electronics Review - 2

Current – put it in terms that a 6th 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

Vi

+

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

Basic Electronics Review - 3 Resistor – put it in terms that a 6th 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

Vi

+

A B

C

D

“High” pressure

“Low” pressure

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

I R

Basic Electronics Review - 5

R1

Vi

+

A

DR3

R2

Vi

+

Req

A

D

Original Circuit Equivalent Circuit

Basic Electronics Review - 6

Power (units are in Watts)P = I2R = (V/R)2R = V2/RP = I2R = I2(V/I) = IV

Note: can calculate thepower required for anycircuit by measuring I andV and taking their product

R1

R2

R3

Vi

+

A B

C

D

Any circuit

I

Capacitor Capacitor– put it in terms that a 6th 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

+ -

2

2

1

1

CVE

idtC

V

dt

dVCi

dt

dQ

CVQ

V

)2cos(2)2sin((

)2sin()sin(

ftfCAdt

ftAdC

dt

dVCi

ftAtAV

Inductor Inductor – put it in terms that a 6th 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

2

2

1

1

LiE

VdtL

i

dt

diLV

V

)2cos(2)2sin((

)2sin()sin(

ftfLAdt

ftAdL

dt

diLV

ftAtAi

The Voltage Divider Consider two resistances in series What is VA in terms of

Vi, R1 and R2Vi

+

A

D

R2

R1

VA

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