Intermediate Robot Building

30 Pages·2013·0.2 MB·English

Intermediate Robot
Building
Second Edition

(cid:2) (cid:2) (cid:2)
David Cook
Intermediate Robot Building, Second Edition
Copyright © 2010 by David Cook
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any
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ISBN-13 (pbk): 978-1-4302-2754-0
ISBN-13 (electronic): 978-1-4302-2755-7
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Technical Reviewer: Scott Parsons
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Jeffrey Pepper, Frank Pohlmann, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft,
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(cid:2) CONTENTS
Contents
(cid:2) Contents.................................................................................................................iii
(cid:2) About the Author................................................................................................xxiv
(cid:2) About the Technical Reviewer............................................................................xxv
(cid:2) Acknowledgments.............................................................................................xxvi
Appreciating Technical Editors......................................................................................xxvi
Getting Support at Work................................................................................................xxvi
Getting Support from the Field......................................................................................xxvi
Support at Home...........................................................................................................xxvii
(cid:2) Introduction.....................................................................................................xxviii
Intended Audience.......................................................................................................xxviii
Prerequisites...........................................................................................................................................xxviii
Required Electronics and Machine Shop Experience.........................................................................xxviii
Required Software Development Experience.......................................................................................xxix
Preferred Robot Building Experience.....................................................................................................xxx
Would LEGO MindStorms Be Better For You?.............................................................................................xxx
Would BEAM Robots Be Better For You?....................................................................................................xxx
No Remote-Controlled Armageddon...........................................................................................................xxx
Volatile Parts..................................................................................................................xxxi
Safety Rules...................................................................................................................xxxi
Preferring the Metric System........................................................................................xxxii
Getting Updates and Seeing What’s New.....................................................................xxxii
iii
(cid:2) CONTENTS
(cid:2) Chapter 1: Assembling a Modular Robot................................................................1
Building Modules...............................................................................................................1
Assembling Roundabout, or Not....................................................................................................................2
Arranging Chapters........................................................................................................................................2
Getting Comfortable with Machining.................................................................................3
Stocking Your Machine Shop.........................................................................................................................3
Looking at a Miniature Milling Machine........................................................................................................5
Using a Milling Machine...........................................................................................................................5
Admitting a Bias Toward Milling...............................................................................................................7
Putting It All Together........................................................................................................7
Grouping Machining Parts.............................................................................................................................8
Grouping Stand-Alone Electronic Modules....................................................................................................8
Assembling and Testing a Robot...................................................................................................................8
Applying Parts and Techniques to Other Robots...............................................................9
(cid:2) Chapter 2: Comparing Two Types of Homemade Motor Couplers and Common
Errors to Avoid......................................................................................................11
Comparing Two Homemade Coupler Technologies.........................................................12
Examining Telescoping-Tube Couplers.......................................................................................................12
Comparing with Solid-Rod Couplers............................................................................................................13
Identifying Desired Results in Coupler Drill Holes,
Along with Common Errors and Their Effects..................................................................14
Connecting the Setscrew Hole to the Motor Shaft Hole..............................................................................15
Aligning the Hole Angles and Hole Centers.................................................................................................16
Accepting Parallel Offset Between the Holes and the Coupler Body......................................................16
Avoiding Parallel Offset Between the Holes Themselves.......................................................................18
Avoiding Angular Offset Between the Holes Themselves.......................................................................19
Reiterating the Advantages of Telescoping Tubing................................................................................21
Getting Ready to Make a Solid-Rod Coupler....................................................................21
iv
(cid:2) CONTENTS
(cid:2) Chapter 3: Making a Fixture and Drilling Solid Rods for a Coupler......................23
Gathering Tools and Parts...............................................................................................23
Preparing Lengths of Solid Rod for the Couplers.............................................................24
Measuring the Motor and Axle....................................................................................................................24
Selecting a Solid Rod for the Coupler Body.................................................................................................25
Calculating the Coupler Length..............................................................................................................25
Calculating the Coupler Diameter...........................................................................................................25
Selecting the Coupler Material...............................................................................................................25
Cutting the Solid Rod into Coupler-Size Pieces...........................................................................................26
Smoothing the Ends of the Coupler Body Pieces.........................................................................................27
Setting Aside the Lengths of Rod................................................................................................................30
Making a Coupler Fixture.................................................................................................30
Cutting the Coupler Fixture Block................................................................................................................31
Drilling the Coupler Fixture Setscrew Hole..................................................................................................33
Tapping the Coupler Fixture Setscrew Hole................................................................................................35
Drilling the Coupler Rod Hole in the Coupler Fixture...................................................................................35
Selecting Drills.......................................................................................................................................36
Fixing the Depth.....................................................................................................................................37
Drilling....................................................................................................................................................40
Getting the Money Shot...................................................................................................41
Enlarging Tight Fits......................................................................................................................................42
Adding a Setscrew to the Coupler Fixture...................................................................................................42
Repositioning the Coupler Fixture...............................................................................................................43
Drilling the Motor-Shaft and LEGO Axle Coupler Holes....................................................43
Swapping Drills, Not Coupler Rods..............................................................................................................46
Add the Finishing Touch: Squaring the Ends...............................................................................................46
Examining the Coupler So Far.........................................................................................46
v
(cid:2) CONTENTS
(cid:2) Chapter 4: Finishing the Solid-Rod Motor Coupler...............................................49
Installing the Coupler Setscrew.......................................................................................49
Determining the Location for the Coupler Setscrew....................................................................................49
Drilling the Coupler Setscrew Hole..............................................................................................................50
Tapping the Coupler Setscrew Hole............................................................................................................51
Selecting a Bottom-Style Tap.................................................................................................................51
Comparing to a Taper-Style Tap.............................................................................................................52
Tapping Tips...........................................................................................................................................53
Selecting a Setscrew...................................................................................................................................53
Adding the LEGO Axle......................................................................................................55
Summary.........................................................................................................................57
(cid:2) Chapter 5: Building a Motor Inside a Wheel.........................................................59
Encountering Danger: Bent Shafts Ahead........................................................................60
Driving Properly with Bearings....................................................................................................................60
Protecting Against Bumps and Falls.......................................................................................................60
Shifting Against the Coupler, Laterally...................................................................................................61
Bending Without Support........................................................................................................................61
Making a Hub-Adapter Coupler.......................................................................................61
Adapting the Motor Shaft’s Outer Diameter to the LEGO Wheel’s Inner Diameter......................................62
Starting Simply with the Coupler Rod..........................................................................................................63
Making the Inner and Outer Hub-Adapter Discs..........................................................................................65
Choosing a Shape...................................................................................................................................65
Determining the Size..............................................................................................................................65
Choosing the Raw Material.....................................................................................................................66
Cutting the Raw Sheet Down to Size......................................................................................................66
Drilling the 1(cid:2)-Inch in Diameter Center Hole...........................................................................................67
4
Again, Why Measure Oversize?..............................................................................................................69
Milling Circles with a Rotary Table.........................................................................................................69
vi
(cid:2) CONTENTS
Drilling Screw Holes in the Discs............................................................................................................73
Finishing the Inner and Outer Hub-Adapter Discs..................................................................................76
Coring the LEGO Hubs..................................................................................................................................78
Securing the Hub During Machining.......................................................................................................79
Selecting a Silver & Deming Drill............................................................................................................80
Drilling Out the Center of the Hub...........................................................................................................80
Sanding Away the Remains of the Center of the Hub.............................................................................81
Fitting and Gluing the Parts Together..........................................................................................................82
Fitting and Gluing the Outer Disc into the Hub.......................................................................................82
Fitting and Gluing the Inner Disc onto the Rod.......................................................................................82
Waiting for Glue to Dry...........................................................................................................................84
Summary.........................................................................................................................84
(cid:2) Chapter 6: Understanding the Standards and Setup for Electronic
Experiments..........................................................................................................85
Reading Schematics........................................................................................................85
Connecting Wires.........................................................................................................................................86
Designating Parts........................................................................................................................................87
Lettering Designations............................................................................................................................87
Numbering Designations........................................................................................................................88
Labeling Parts..............................................................................................................................................88
Labeling Resistors..................................................................................................................................89
Labeling Capacitors................................................................................................................................91
Labeling LEDs and IEDs..........................................................................................................................93
Labeling Other Parts...............................................................................................................................94
Specifying Power Supply.............................................................................................................................94
Simplifying the Positive Voltage Supply Label........................................................................................94
Symbolizing Ground and Simplifying Wiring...........................................................................................94
Using Solderless Breadboards.........................................................................................95
Selecting a Solderless Breadboard.............................................................................................................96
vii
(cid:2) CONTENTS
Setting Up a Solderless Breadboard to Match the Photographs.................................................................97
Powering a Solderless Breadboard........................................................................................................98
Selecting an AC Power Adapter..............................................................................................................98
Adding a Few Amenities.......................................................................................................................100
Understanding Oscilloscope Traces...............................................................................101
Riding the Bandwagon of Modern Electronics...............................................................102
Getting Past the Learning Curve Barrier....................................................................................................102
Avoiding Obsolete Technology...................................................................................................................102
Using Surface-Mount Components............................................................................................................102
Sizing Down Surface-Mount.................................................................................................................103
Saying “Good-Bye” to Through-Hole....................................................................................................104
Working with Surface-Mount Components..........................................................................................104
Converting Surface-Mount Components to Through-Hole....................................................................104
Mixing and Matching Package Technologies.......................................................................................106
Shrinking Below Hand-Labor Level......................................................................................................106
Summary.......................................................................................................................106
(cid:2) Chapter 7: Creating a Linear Voltage- Regulated Power Supply........................107
Understanding Voltage Regulators................................................................................107
Understanding Linear Voltage-Regulated Power Supplies............................................108
The 7805 Linear Voltage Regulator...........................................................................................................108
Introducing a 7805-Based 5 V Power Supply.......................................................................................109
Building the 7805-Based Power Supply...............................................................................................111
Improving the Power Supply by Reducing the Minimum Required Unregulated Voltage..........................113
Substituting an LM2940, MCP1702, or LP2954 for the 7805................................................................114
Substituting a Power MOSFET for the 1N5817.....................................................................................115
Increasing Resistance at Lower Voltages.............................................................................................117
Selecting a Low-Resistance P-Channel Power MOSFET......................................................................117
Analyzing the Minimum Input Voltage of Various Linear Regulator Circuits.........................................118
Presenting the Input/Output Voltage Results of Three 5 V Linear Voltage Regulators.........................122
viii
(cid:2) CONTENTS
Considering Various Factors in Linear Voltage Regulators........................................................................124
Protecting Against a Reverse Battery...................................................................................................124
Protecting Against Short Circuits..........................................................................................................124
Protecting Against Thermal Overload...................................................................................................125
Simplicity and Low Cost of a Complete Circuit.....................................................................................126
Consuming Quiescent Current..............................................................................................................126
Isolating Power and Noise....................................................................................................................126
Selecting a Linear Voltage Regulator for Your Robot............................................................................128
Changing Marketplace Is Limiting 5 V Linear Regulator Selection............................................................129
Heading into Optimizations............................................................................................130
(cid:2) Chapter 8: Making Robot Power Supply Improvements.....................................131
Bulking Up the Input and Output Capacitors..................................................................131
Increasing Battery Lifetime with Bulk Capacitors.....................................................................................133
Delayed Power-Off Because of Bulk Capacitors........................................................................................133
Using a DPDT Power Switch to Reduce Turn-Off Time..............................................................................135
Selecting Bulk Capacitors..........................................................................................................................136
Implementing Higher Margins of Safety for Tantalum Capacitors.............................................................136
Adding Voodoo Capacitors.............................................................................................137
Sprinkling with Bypass/Decoupling Capacitors.............................................................138
Bypassing the Long Path to the Power Supply.....................................................................................139
Decoupling Noise at Each Source.........................................................................................................140
Selecting Bypass/Decoupling Capacitors.............................................................................................140
Preventing Damage from Short Circuits or Overcurrent................................................141
Deciding If Overcurrent Protection Is Required.........................................................................................141
Protecting with a Fuse...............................................................................................................................141
Protecting with a Manually Reset Circuit Breaker.....................................................................................142
Protecting Robots from Short Circuits and Overcurrents with a
Solid-State Auto-Resetting PPTC Device...................................................................................................142
Greatly Increasing Resistance to Greatly Reduce Current....................................................................142
ix
(cid:2) CONTENTS
Installing PPTC Overcurrent-Protection Devices...................................................................................143
Selecting PPTC Overcurrent-Protection Devices..................................................................................145
Preventing Damage from Overvoltage in a Regulated Circuit........................................146
Introducing the Zener Diode......................................................................................................................146
Using a Zener Diode to Short Circuit Power Upon Overvoltage.................................................................147
Tripping Overcurrent Protection with the Overvoltage Short Circuit....................................................148
Taking One for the Team: The Sacrificial Death of Mr. Zener...............................................................149
Choosing an Appropriate Breakdown Voltage...........................................................................................149
Purchasing Zener Diodes...........................................................................................................................149
Putting It All Together for a Robust Robot Power Supply..............................................150
(cid:2) Chapter 9: Driving Miss Motor............................................................................153
Why a Motor Driver?......................................................................................................153
Running Motors at Higher Voltages Than Logic Chips Can Provide...........................................................154
Supplying More Current to Motors Than Logic Chips Can Provide............................................................154
Causing Logic Errors with Motor Noise.....................................................................................................154
Supplying Motor Power from Unregulated vs. Regulated Power...............................................................154
Demonstrating the Four Modes of a Motor....................................................................155
Rotating Clockwise....................................................................................................................................156
Rotating Counterclockwise........................................................................................................................157
Rotating Freely/Coasting (Slow Decay).....................................................................................................157
Braking/Stopping (Fast Decay)..................................................................................................................157
Using Up More Energy..........................................................................................................................157
Braking by Fast Decay..........................................................................................................................158
Driving Simply with a Single Transistor.........................................................................158
Introducing the NPN Bipolar Single-Transistor Motor-Driver Circuit.........................................................160
Switching with a Transistor..................................................................................................................161
Using Transistors As Off/On Switches, Not Amplifiers, in Motor-Driver Circuits..................................161
Limiting Base Current with a Resistor..................................................................................................161
Protecting the Transistor with a Diode.................................................................................................162
x