Abstract
Teaching
laboratory
electronics
in
a
general
physics
laboratory
classroom
requires
hauling
hundreds
of
pounds
of
apparatus
from
stockroom
to
lab
bench
and
back
each
day.
Some
students
see
the
equipment
as
"magical
mystery
boxes"
that
must
be
connected
in
just
the
right
way
to
func?on
properly.
Such
abstrac?on
can
be
an
impediment
to
learning
electronic
principles.
CSUCI
is
exploring
an
alterna?ve,
where
the
students
design
and
build
a
very
compact
and
simple
"open"
electronics
workbench
with
adjustable
DC
power
supplies,
a
versa?le
func?on
generator,
an
audio
amplifier,
and
a
solderless
breadboard.
They
construct
all
of
this
on
a
small
perforated
circuit
board
for
~$25.
Along
with
a
digital
mul?meter
(~
$10),
they
are
able
to
build,
troubleshoot,
and
study
a
wide
variety
of
circuits
without
an
oscilloscope
or
other
apparatus.
Dr.
Rasnow
will
present
the
results
and
lessons
learned
from
this
experimental
curriculum.
0
Do‐it‐Yourself
Electronics
Laboratory
Brian
Rasnow
Dept.
of
Physics
California
State
University
Channel
Islands
1
C.S.U. Channel Islands
New Course * Spring 2009
Phys 310 Electronics
A
new
class
in
new
major
in
a
new
(small)
school
required
recrui?ng
students
from
other
science
majors
Do you wonder how gadgets work? How to fix broken stereos, Ipods, computers?
How to design sensors, actuators, control systems, or computers?
This new course explores electronics
• from simple devices to complex instruments
• from wavefunctions to software
• mixing theory with practical methods
We will
• build amplifiers, transducers, rail guns, microcontrollers
• measure the speed of light
• fix broken Ipods, computers, stereos
4 Units, M 10-11:50 am & W 9 – 11:50 am
Prerequisites Phys 101 or 201. All majors welcome.
For further information:
http://phys106fall08.wetpaint.com/page/Basic+Electronics
Prof. Brian Rasnow brian.rasnow@csuci.edu
2
Class
philosophy
•  Electronics
is
hard
to
learn
–  No
innate
sense
of
weak
electricity
•  Rely
on
machines
to
detect
it
–  Abstract
and
unintui?ve
•  Different
physics
than
our
innate
senses
–  Daun?ng
complexity
•  Technology
provides
us
with
a
smorgasbord
of
devices
with
various
behaviors
•  But
learning
how
to
learn
about
electronics
will
help
you
learn
about
other
complex,
unintui?ve
systems
in
life
3
Our
Approach
•  Emphasize
lab
ac?vi?es
–  Build
prac?cal
understanding
–  Build
hands‐on
skills
•  Key
to
understanding
advanced
electronics
topics
are
–  Understand
basic
concepts
–  Learn
the
art
of
measurement
•  Using
a
voltmeter
&
oscilloscope
•  What
to
do
when
things
don’t
work
–
–
–
–
Iden?fy
simple
circuits
and
learn
to
parse
schema?cs
Familiarity
with
simple
components
Art
of
building,
tes?ng,
designing
Keeping
it
simple
with
hierarchical
abstrac/on
4
First
ac?vity:
Baberies
&
bulbs
•  What
general
rules
predict
circuit
behavior?
•  How
do
voltage
and
current
help
predict
circuit
behavior?
–  How
can
we
frame
general
rules
in
terms
of
these
abstract
concepts?
–  What
evidence
do
we
have
that
electrons
exist?
•  What
excep?ons
to
these
rules
are
there?
–  Where
do
the
rules
break
down?
E.g.,
Jacob’s
ladder
5
Mystery
Boxes
•  Can
you
figure
out
what’s
inside
each
of
these
boxes?
•  Draw
the
schema?cs
for
the
simplest
circuit
within
each
and
explain
how
you
concluded
that.
A
?
=
•  To
solve
this,
we
built
crude
voltmeters
and
ohmmeters
with
light
bulbs
and
baberies.
•  Abstrac?on
is
obvious.
6
Mul?meters
•  Explore
a
mul?meter
–  Human
interface
and
electric
interface
to
measure
…
•  How
can
you
damage
one?
•  How
can
one
damage
you?
7
Variable
DC
power
supply
•  Explore
a
variable
DC
power
supply
–  Human
interface
and
electric
interface
•  How
can
you
damage
one?
•  How
can
one
damage
you?
8
Func?on
Generator
•  Explore
a
func?on
generator
–  Human
interface
and
electric
interface
•  How
can
you
damage
one?
•  How
can
one
damage
you?
Oscilloscope
•  Explore
a
scope
–  Human
interface
and
electric
interface
–  Both
are
quite
complex
•  How
can
you
damage
one?
•  How
can
one
damage
you?
9
Circuits
labs
•  We
used
these
apparatus
to
explore
Ohm’s
law,
voltage
dividers,
and
simple
resistor,
capacitor,
inductor,
diode,
transistor,
and
FET
circuits
10
Component
transfer
func?ons
•  A
major
goal
of
the
labs
is
to
explore/discover
the
characteris?cs
of
components
&
their
innumerable
combina?ons
in
circuits
…
11
Logis?cs
&
Abstrac?on
•  Moving
>100
pounds
of
mul?meters,
power
supplies,
func?on
generators,
and
oscilloscopes
back
and
forth
from
cabinets
to
classroom
and
lab
bench
was
becoming
a
burden
–  Doing
the
simplest
experiment
was
onerous
•  Some
students
perceived
the
labs
as
exercises
in
how
to
connect
these
magical
boxes
together
to
achieve
a
desired
state
–  Their
understanding
of
what
their
apparatus
did
was
lacking
–  The
apparatus
was
obviously
complex
and
expensive,
and
in?mida?ng
12
Matlab
Simula?on
•  Simula?on
solves
the
logis?cs
problem,
but
its
abstract
Produces:
>>
|Vr|
=
3.0V,
phase
=
82.8deg
at
1kHz
>>
|Vr|
=
18.8V,
phase
=
38.5deg
at
10kHz
13
Bode
Plot
•  Approximately
piecewise
linear
behavior
on
loglog
amplitude
and
log‐linear
phase
plots
allows
for
graphical
es/mates
of
complex
circuits
“corner
frequency”
14
Time
domain
•  Simula?ng
waveforms
that
match
oscilloscope
data
makes
the
simula?ons
more
credible
•  This
Matlab
func?on
f2t()
converts
from
frequency
domain
to
?me
domain,
with
the
inverse
Fourier
transform
(ifft)
15
Simulated
waveforms
•  Sine
waves
are
eigenfunc?ons
of
linear
circuits
•  But
we
want
to
get
more
hands‐on
16
Individual
/
class
project
•  Objec?ve:
We
will
each
build
our
own
mul?‐output
DC
power
supply,
func?on
generator,
and
audio
amplifier,
as
a
convenient,
compact,
affordable
test
bed
for
exploring
simple
electronic
circuits.
We
will
learn
many
prac?cal
lessons
in
the
process
of
design,
prototyping,
construc?on,
and
debugging,
and
ul?mately
using
the
system
for
future
labs.
•  Design
Specifica?ons:
–  size
<6"x8"x3”;
weight
<2lbs;
cost
of
materials
<$30
–  DC
power
supplies:
•  +
&–
12VDC
constant
voltage
at
0‐100mA,
<10mV
ripple
and
noise
•  +&‐
1.2‐15VDC
variable
at
0‐100mA
–  Func?on
generator:
10‐100kHz;
0‐10V
amplitude;
sine,
triangle,
square
wave
–  Audio
amplifier:
protected
input;
0.05‐50,000
gain;
50Hz
‐
15kHz
bandwidth
17
Methods
•  Designs
modified
from
datasheets
found
online
–
–
–
–
–
3
pin
voltage
regulators:
7812,
7912,
LM317,
LM337
Transformer
specs
and
RMS
Exar
XR2206
func?on
generator
LM386
audio
amplifier
Prototyped
designs
on
solderless
breadboard
•  Learned
where
to
acquire
parts:
–  Ebay,
www.allelectronics.com,
www.futureelectronics.com,
etc.
–  Recycled
from
consumer
electronics
–  We
needed
to
be
extremely
frugal
to
meet
budget
constraints
•  Construc?on:
–  perforated
circuit
breadboard
–  Posi?ve
photoresist
single
sided
PCB
–  Small
solderless
breadboard
•  “Bootstrapped”
approach
18
Interfaces
•  Inputs
–  Power
plug
–  Audio
input
–  Solderless
breadboard
•  Outputs
–
–
–
–
–
–
+/‐12V,
+/‐1.2‐15V
Fgen
out
Sync
out
Speaker
LED
indicator
Solderless
breadboard
•  Controls
–
–
–
–
–
+/‐
V
=
5k
pots
Frequency
=
500k
pot
Amplitude
=
50k
pot
DC
offset
=
50k
pot
Volume
50k
pot
19
Power
supply
schema?c
Note
polarity
of
caps.
The
pinouts
of
each
voltage
regulator
is
different!
Why
are
there
two
1k
resistors
in
series
with
the
LED?
Why
is
it
on
the
nega?ve
supply?
20
Layout
•  Power
supply
occupies
~1/4
of
the
circuit
board
•  It
is
powering
prototyped
func?on
generator
on
a
small
solderless
breadboard
21
Construc?on
+12
‐12
gnd
gnd
‐V
+V
Power
LED
22
Power
supply
solder
side
•  Note:
By
careful
layout,
only
two
traces
cross
others
•  One
trace
is
more
common
than
others,
hence
it’s
called
“common”
or
“ground”.
23
Power
supply
solder
side
•  Note:
By
careful
layout,
only
two
traces
cross
others
•  One
trace
is
more
common
than
others,
hence
it’s
called
“common”
or
“ground”.
•  If
this
were
a
printed
circuit,
this
conductor
could
cover
much
of
the
board.
24
X‐ray
view
25
Func?on
generator
schema?c
•  First
prototype
is
the
simplest
circuit
from
Figs.
2
&
11
of
the
data
sheet.
•  f
=
1/RC
200
fmin
=
100Hz
fmax
=
100kHz
w/.01uf
•  Sine
output
is
offset
by
Vcc/2
•  Square
output
is
open‐
collector
3
26
Func?on
Generator
prototype
sqr
out
•  Verify
sine
and
square
wave
outputs
on
a
scope,
&
both
pots
work
as
expected
(volume
and
frequency
increase
clockwise).
•  What
changes
or
features
should
we
consider?
•  How
will
we
lay
this
circuit
out
to
solder
(with
minimal
crossing
of
wires)?
amplitude
Sine
out
+12
Gnd
freq
27
Final
design
Freq
•  This
circuit
produces
~100Hz‐100kHz
sine,
triangle,
and
square
waves
with
adjustable
frequency,
amplitude,
and
DC
offset.
•  Breadboard
the
upper
le{
part
first,
then
we’ll
build
it
on
a
printed
circuit
board
10k
28
PCB
design
•  Printed
circuit
board,
designed
in
Adobe
Illustrator,
implements
all
interconnec?ons
but
2
(blue)
on
one
side
of
a
2”x2”
copper
clad
circuit
board.
•  Component
side
view
with
copper
pabern
grayed.
Grid
is
100
mil
(.1”).
•  Note
that
traces
generally
run
ver?cally
and
“vias”
(blue)
are
horizontal.
Geometry
does
maber
in
this
physical
abstrac?on
of
the
circuit.
29
Design
ques?ons
•  Do
you
understand
…
–
–
–
–
–
–
–
–
What
is
the
theore?cal
maximum
and
minimum
frequency?
Why
R1
+
R2
(i.e.,
isn’t
R2
<<
R1,
so
why
is
it
there?)
Why
R3
||
R4
(vs.
one
resistor?)
What’s
the
role
of
R5
and
the
Zener?
Why
isn’t
R5
10k
or
1k?
Hint:
you’ll
need
to
understand
the
“open
collector”
configura?on
inside
pin
11.
Why
is
R6
fixed
instead
of
variable
as
in
most
circuits
in
the
datasheet?
What
is
the
role
of
C4?
What
constrains
the
values
of
C4
and
R9?
What
is
the
op
amp
gain?
Phase?
Vs.
frequency?
Might
there
be
a
problem
with
the
polarity
of
C4?
30
PCB
layout
•  6
func?on
generators
fit
on
a
4”x6”
circuit
board.
–  Large
ground
plane
(and
V+)
minimizes
etching
–  Etched
component
holes
are
drill
guides
•  To
make
a
printed
circuit
board:
1.  Print
this
pabern
on
transparency
film
2.  Place
film
on
photoresist
3.  Expose
to
sunlight
(exposure
determined
empirically,
~1
min)
4.  Develop
to
remove
exposed
photoresist
5.  Examine,
touch
up
errors
(with
Sharpie)
Write
your
ini?als
or
name
with
Sharpie
6.  Etch
unprotected
copper
7.  Drill
8.  Scrape
or
dissolve
photoresist
(acetone)
9.  Place
components
and
solder
10. 
Clean
and
test
31
PCB
construc?on
1.
Developed
photoresist
2.
Etched
bare
copper 3.
Drilled
4.
Removed
photoresist
5.
Soldered
components
6.
Component
side 32
Func?on
generator
pcb
33
Mounted
on
motherboard
Wires
holding
it
down
34
Some
lessons
learned
•  Hands‐on
experiences
and
building
useful
things
was
rewarding
and
engaging
–  This
was
the
first
?me
most
students
used
a
soldering
iron
&
drill
press
–  Conver?ng
recycled
AC
or
DC
adapters
into
LED
night
lights
was
“cool”
–  Building
from
scratch
and
owning
sophis?cated
test
equipment
was
cool
•  The
art
of
compromise
in
engineering
was
repeatedly
experienced
–  Cost,
simplicity,
robustness,
user‐friendliness,
capabili?es
are
traded
off
•  Building
power
supplies
demys?fied
what
a
power
supply
does
–  Undersizing
filter
capacitors
let
the
students
see
poor
regula?on
–  The
adjustable
supplies
were
not
necessary
•  Building
the
func?on
generator
and
audio
amp
let
students
explore
many
devices
and
circuits
without
using
any
school
equipment
–  This
appeared
to
empower
and
mo?vate
some
to
explore
more
35
More
lessons
•  Soldering
is
a
skill
picked
up
by
some
students
faster
than
others,
and
it
takes
?me
–  Soldering
the
PCB
was
much
quicker
and
easier
than
the
perf
board
•  Layout
is
also
a
slowly
learned
skill
–
visualizing
top
and
bobom
simultaneously
–  Could
it
help
to
build
the
PCB
before
the
PS?
•  A
walk‐in,
open
lab
bench,
equipped
with
soldering
sta?on,
oscilloscope,
voltmeter,
tools
and
parts,
helped
students
complete
their
projects
outside
of
class
•  Tried
to
engage
the
class
in
debugging
individual
boards
36
Other
topics
explored
•  Transistors
&
FETs
in
satura?on
and
op‐amp
comparators
segued
to
the
digital
abstrac?on
–  Explored
the
Arduino
microcontroller
•  Appreciate
the
computa?onal
power
of
feedback
–  Read
Braitenberg’s
“Vehicles”
•  Time
domain
reflectometry
(without
a
TDR)
–  Measued
speed
of
light
&
length
of
a
wire
–  Related
to
SWR
and
radio
•  Transducers:
sensors
and
actuators
37
Final
comments
•  Low
enrollment
and
haven’t
collected
final
lab
reports
to
more
formally
assess
student
outcomes
•  Didn’t
get
any
ipods
or
home
electronics
to
explore
•  Can
beber
CAD
tools
be
incorporated
in
the
class?
•  Building
the
PS/func?on
generator
circuits
was
the
high
point
of
the
class
•  Some
students
bought
used
oscilloscopes
for
<$100
•  Hopefully
they’ll
con?nue
exploring
electronics!
38
References
&
Acknowledgements
•
•
•
•
•
•
•
•
Horowitz
&
Hill,
“The
Art
of
Electronics”
A.
Agarwal,
MIT
Open
Courseware,
6.002
Circuits
and
Electronics
R.
Middlebrook,
Design‐oriented
Analysis
Paradigm
V.
Braitenberg
“Vehicles:
Experiments
in
Synthe?c
Psychology”
Circuit
cellar
magazine
&
website
The
Arduino
online
community
CSUCI
Physics
Dept.
Students
of
Phys
310
Thank
you!
Ques?ons?
39