03-11-2012, 01:35 PM
Lessons In Electric Circuits, Volume VI – Experiments
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Electronics as science
Electronics is a science, and a very accessible science at that. With other areas of scientific
study, expensive equipment is generally required to perform any non-trivial experiments. Not
so with electronics. Many advanced concepts may be explored using parts and equipment
totaling under a few hundred US dollars. This is good, because hands-on experimentation is
vital to gaining scientific knowledge about any subject.
When I started writing Lessons In Electric Circuits, my intent was to create a textbook
suitable for introductory college use. However, being mostly self-taught in electronics myself,
I knew the value of a good textbook to hobbyists and experimenters not enrolled in any formal
electronics course. Many people selflessly volunteered their time and expertise in helping me
learn electronics when I was younger, and my intent is to honor their service and love by giving
back to the world what they gave to me.
In order for someone to teach themselves a science such as electronics, they must engage in
hands-on experimentation. Knowledge gleaned from books alone has limited use, especially in
scientific endeavors. If my contribution to society is to be complete, I must include a guide to
experimentation along with the text(s) on theory, so that the individual learning on their own
has a resource to guide their experimental adventures.
Setting up a home lab
In order to build the circuits described in this volume, you will need a small work area, as
well as a few tools and critical supplies. This section describes the setup of a home electronics
laboratory.
Work area
A work area should consist of a large workbench, desk, or table (preferably wooden) for performing
circuit assembly, with household electrical power (120 volts AC) readily accessible to
power soldering equipment, power supplies, and any test equipment. Inexpensive desks intended
for computer use function very well for this purpose. Avoid a metal-surface desk, as the
electrical conductivity of a metal surface creates both a shock hazard and the very distinct possibility
of unintentional ”short circuits” developing from circuit components touching the metal
tabletop. Vinyl and plastic bench surfaces are to be avoided for their ability to generate and
store large static-electric charges, which may damage sensitive electronic components. Also,
these materials melt easily when exposed to hot soldering irons and molten solder droplets.
If you cannot obtain a wooden-surface workbench, you may turn any form of table or desk
into one by laying a piece of plywood on top. If you are reasonably skilled with woodworking
tools, you may construct your own desk using plywood and 2x4 boards.
The work area should be well-lit and comfortable. I have a small radio set up on my own
workbench for listening to music or news as I experiment. My own workbench has a ”power
strip” receptacle and switch assembly mounted to the underside, into which I plug all 120
volt devices. It is convenient to have a single switch for shutting off all power in case of an
accidental short-circuit!
Tools
A few tools are required for basic electronics work. Most of these tools are inexpensive and easy
to obtain. If you desire to keep the cost as low as possible, you might want to search for them
at thrift stores and pawn shops before buying them new. As you can tell from the photographs,
some of my own tools are rather old but function well nonetheless.
First and foremost in your tool collection is a multimeter. This is an electrical instrument
designed to measure voltage, current, resistance, and often other variables as well. Multimeters
are manufactured in both digital and analog form. A digital multimeter is preferred for
precision work, but analog meters are also useful for gaining an intuitive understanding of
instrument sensitivity and range.
INSTRUCTIONS
In all the experiments in this book, you will be using some sort of test equipment to measure
aspects of electricity you cannot directly see, feel, hear, taste, or smell. Electricity – at least in
small, safe quantities – is insensible by our human bodies. Yourmost fundamental ”eyes” in the
world of electricity and electronics will be a device called a multimeter. Multimeters indicate
the presence of, and measure the quantity of, electrical properties such as voltage, current, and
resistance. In this experiment, you will familiarize yourself with the measurement of voltage.
Voltage is the measure of electrical ”push” ready to motivate electrons to move through a
conductor. In scientific terms, it is the specific energy per unit charge, mathematically defined
as joules per coulomb. It is analogous to pressure in a fluid system: the force that moves fluid
through a pipe, and is measured in the unit of the Volt (V).
Your multimeter should come with some basic instructions. Read them well! If your multimeter
is digital, it will require a small battery to operate. If it is analog, it does not need a
battery to measure voltage.
Some digital multimeters are autoranging. An autoranging meter has only a few selector
switch (dial) positions. Manual-ranging meters have several different selector positions
for each basic quantity: several for voltage, several for current, and several for resistance.
Autoranging is usually found on only the more expensive digital meters, and is to manual
ranging as an automatic transmission is to a manual transmission in a car. An autoranging
meter ”shifts gears” automatically to find the best measurement range to display the particular
quantity being measured.