Make: Electronics

by Charles Platt

  Putting this procedure into a controller chip not only simplifies the circuit, but offers another advantage: you can change the combination simply by rewriting the program and downloading the new version into the chip.

  Figure 5-148. This screenshot shows the complete listing of a program to read a sequence of three keypresses in conjunction with a combination lock. If the sequence is correct, the PICAXE sends a high output from one of its pins. If the sequence is incorrect, the program loops back to the beginning.

  Fundamentals

  Limitations of MCUs

  The PICAXE does have some disadvantages. Its voltage requirements alone restrict you from using it with the kind of freedom of a 555 timer.

  Also, although I can get an instant result by plugging a 555 timer into a breadboard and adding a couple of resistors and a couple of capacitors, the PICAXE requires me to add a download socket, hook it up to my computer, write a program in the Programming Editor, and download the program.

  Some people don’t like writing software, or they have difficulty thinking in the relentlessly left-brain way that computer programming requires. They may prefer the hands-on process of assembling hardware.

  Other people may have the opposite preference. This of course is a matter of taste, but one thing we know beyond all doubt is that computer programs often contain errors that may not reveal themselves until weeks or months later.

  The PICAXE, for instance, doesn’t protect you if a number is assigned to a variable that exceeds the limit for that type of variable. Suppose b1=200 and b2=60 and your program tells the PICAXE:

  let b3 = b1 + b2

  The result should be 260, but byte-size variables can only count up to 255. What happens? You will find that b3 acquires a value of 4, without any warning or explanation. This is known as an “overflow error,” which can be very difficult to predict, because it happens at runtime, when external factors are in control. The code looks perfectly good; the Programming Editor doesn’t find any syntax errors; the simulation behaves properly. But in the real world, days or even months later, an unexpected set of circumstances results in an input that causes the overflow, and because the code is residing inside the chip at this point, you may have a hard time figuring out what on earth went wrong.

  Software has its problems. Hardware has its advantages.

  Fundamentals

  Unexplored territory

  If you’ve taken the time to complete most of the projects in this book with your own hands, you have gained a very rapid introduction to the most fundamental areas of electronics.

  What have you missed along the way? Here are some topics that remain wide open for you to explore. Naturally you should search online if they interest you.

  The informal, learning-by-discovery approach that I have used in this book tends to be light on theory. I’ve avoided most of the math that you’d be expected to learn in a more rigorous course on the subject. If you have mathematical aptitude, you can use it to gain a much deeper insight into the way in which circuits work.

  I didn’t deal much with computer architecture, either. We didn’t go very far into binary code, and you didn’t build a half-adder, which is a great way to learn how computers function on the most fundamental level. Perhaps you should think about assembling one.

  I avoided going deeply into the fascinating and mysterious properties of alternating current. Here again, some math is involved, but just the behavior of current at high frequencies is an interesting topic in itself.

  For reasons already stated, I avoided surface-mount components—but you can still go into this area yourself for a relatively small investment, if you like the idea of creating fascinatingly tiny devices. This may be the future of hobby electronics, so if you stick with it, you’ll probably end up in the world of surface-mount.

  Vacuum tubes were not mentioned, because at this point, they are mainly of historical interest. But there’s something very special and beautiful about tubes, especially if you can enclose them in fancy cabinetwork. In the hands of a skilled craftsperson, tube amplifiers and radios become art objects.

  I didn’t show you how to etch your own printed circuit boards. This is a task that appeals to only certain people, and the preparation for it requires you to make very neat drawings or use computer software for that purpose. If you happen to have those resources, you might want to do your own etching. It could be a first step toward mass-producing your own devices.

  I didn’t cover static electricity at all. High-voltage sparks don’t have any practical applications, and they entail some safety issues—but they are stunningly impressive, and you can easily obtain the necessary information to build the equipment. Maybe you should try.

  Other Controllers

  If you want something more powerful, a BASIC Stamp is the logical next step after a PICAXE. the BASIC Stamp is so called because it originally looked like a postage stamp. The BASIC Stamp has a larger vocabulary of commands and a bigger range of add-on devices (including displays with graphical capability, and a little keyboard that is specifically designed for use with the controller). The BASIC Stamp is shown in Figure 5-149.

  Figure 5-149. The BASIC Stamp controller consists of surface-mounted components on a platform that has pins spaced at 1/10-inch intervals, for insertion in a breadboard or perforated board. This component uses a version of BASIC that is similar to the programming language of the PICAXE, but has many more extensions. The BASIC Stamp is available for use with a wide range of peripheral devices, including many alphanumeric dot-matrix displays.

  On the downside, you’ll find that everything associated with the BASIC Stamp is a bit more expensive than in the PICAXE world, and the download procedure isn’t quite as simple.

  One of the more recent developments in the world of MCUs is the Arduino, which is both sophisticated and powerful. It does require programming in the C language. This language is a little more difficult to understand, and has only the vaguest similarity to the syntax that is used in the PICAXE and BASIC Stamp. On the other hand, because C dominates the larger world of computing, learning it might not be such a bad idea—and the Arduino offers some truly amazing capabilities. Because it is so popular, there are also many software tools, documentation, user forums, and many enthusatic hobbyists to help you. Two other Make: Books titles that I mentioned previously, Getting Started with Arduino and Making Things Talk, provide a great introduction.

  In Closing

  I believe that the purpose of an introductory book is to give you a taste of a wide range of possibilities, leaving you to decide for yourself what you want to explore next. Electronics is ideal for those of us who like to do things ourselves, because almost any application—from robotics, to radio-controlled aircraft, to telecommunications, to computing hardware—allows opportunities that we can explore at home, with limited resources.

  As you delve deeper into the areas of electronics that interest you most, I trust you’ll have a satisfying learning experience. But most of all, I hope you have lots of fun along the way.

  Appendix. Online Retail Sources and Manufacturers

  This appendix contains URLs for companies mentioned as retail sources or manufacturers, along with the commonly used name of the source and the company name.

  Colloquially used name

  Actual corporate or company name

  URL

  3M

  Minnesota Mining and Manufacturing Co.

  http://solutions.3m.com/en_US/

  Ace Hardware

  Ace Hardware Corporation

  http://www.acehardware.com

  Adva
nced Micro Circuits

  Advanced Micro Circuits Corp

  http://www.advancedmicrocircuits.com

  Akro-Mils

  Myers Industries, Inc.

  http://www.akro-mils.com

  Alcoswitch

  Division of Tyco Electronics Corporation

  http://www.tycoelectronics.com/catalog/menu/en/18025

  All Electronics

  All Electronics Corporation

  http://www.allelectronics.com

  All Spectrum Electronics

  All Spectrum Electronics

  http://www.allspectrum.com

  All-Battery.com

  Tenergy Corporation

  http://www.all-battery.com

  Alpha potentiometers

  Alpha Products Inc.

  http://www.alphapotentiometers.net

  ALPS pushbutton

  ALPS Electric Co., Ltd.

  http://www.alps.com

  Amazon

  Amazon.com, Inc.

  http://www.amazon.com

  Amprobe

  Amprobe Test Tools

  http://www.amprobe.com

  Arduino

  No corporate identity

  http://www.arduino.cc

  ArtCity

  ArtCity

  http://www.artcity.com

  AutoZone

  AutoZone, Inc.

  http://www.autozone.com

  Avago

  Avago Technologies

  http://www.avagotech.com

  BASIC Stamp

  Brand owned by Parallax, Inc.

  http://www.parallax.com

  BI Technologies

  BI Technologies Corporation

  http://www.bitechnologies.com

  BK Precision

  B&K Precision Corp.

  http://www.bkprecision.com

  Bussmann fuses

  Cooper Bussman, Inc.

  http://www.cooperbussmann.com

  C&K switch

  CoActive Technologies, Inc.

  http://www.ck-components.com

  Chicago lighting

  CML Innovative Technologies

  http://www.cml-it.com

  CraftAmerica

  Cardinal Enterprises

  http://www.craftamerica.com

  Darice

  Darice Inc.

  http://www.darice.com

  DeWalt

  DeWalt Industrial Tool Company

  http://www.dewalt.com

  Digi-Key

  Digi-Key Corporation

  http://www.digikey.com

  Directed switches

  Directed Electronics Inc.

  http://www.directed.com

  Doctronics

  Doctronics Educational Publishing

  http://www.doctronics.co.uk

  eBay

  eBay Inc.

  http://www.ebay.com

  Elenco

  Elenco Electronics Inc.

  http://www.elenco.com

  Everlight

  Everlight Electronic Co. Ltd.

  http://www.everlight.com

  Extech

  Extech Instruments Corporation

  http://www.extech.com

  Fairchild

  Fairchild Semiconductor Incorporated

  http://www.fairchildsemi.com

  FTM

  FTM Incorporated

  http://thefabricatorssource.com

  Fujitsu

  Fujitsu America, Inc.

  http://www.fujitsu.com/us/

  GB wire strippers

  Gardner Bender Inc.

  http://www.gardnerbender.com

  Hobbylinc

  Hobbylinc Hobbies

  http://www.hobbylinc.com

  Home Depot

  Homer TLC, Inc.

  http://www.homedepot.com

  Ideal wire strippers

  Ideal Industries Inc.

  http://www.idealindustries.com

  Jameco

  Jameco Electronics

  http://www.jameco.com

  K&J Magnetics

  K&J Magnetics Inc.

  http://www.kjmagnetics.com

  Kingbright

  Kingbright Corporation

  http://www.kingbrightusa.com

  Kobiconn

  No web page found; use mouser.com

  KVM Tools

  KVM Tools Inc.

  http://www.kvmtools.com

  Lowe‚Äôs hardware

  LF, LLC

  http://www.lowes.com

  Lumex

  Lumex Inc.

  http://www.lumex.com

  McMaster-Carr

  McMaster-Carr Supply Company

  http://www.mcmaster.com

  Megahobby

  Megahobby.com

  http://www.megahobby.com

  Meter Superstore

  Division of SRS Market Solutions Inc.

  http://www.metersuperstore.com

  Michaels craft stores

  Michaels Stores, Inc.

  http://www.michaelscrafts.com

 
Mill-Max

  Mill-Max Manufacturing Corp.

  http://www.mill-max.com

  Mitutoyo

  Mitutoyo America Corporation

  http://www.mitutoyo.com

  Motorola

  Motorola, Inc.

  http://www.motorola.com/us

  Mouser electronics

  Mouser Electronics, Inc.

  http://www.mouser.com

  Mueller alligator clip

  Mueller Electric Company

  http://www.muellerelectric.com

  Newark

  Subsidiary of Premier Farnell plc

  http://www.newark.com

  NKK switches

  Nihon Kaiheiki Industry Co. Ltd.

  http://www.nkkswitches.com

  NXP semiconductors

  NXP Semiconductors

  http://www.nxp.com

  Omron

  Omron Corporation