Experiment Manual Sample Pages (PDF) - Thames & Kosmos

electronics
Experiment Manual

electronics
The Components . . . . . . . . . . . . . . . . . . . . . . . . 2
A Robot is Born . . . . . . . . . . . . . . . . . . . . . . . . . 6
Assembling the Console . . . . . . . . . . . . . . . . .8
The First Experiments . . . . . . . . . . . . . . . . . .10
The Circuit Diagram . . . . . . . . . . . . . . . . . . .12
Circuits Are Closed Loops . . . . . . . . . . . . . . .12
Adding a Jumper Wire . . . . . . . . . . . . . . . . .13
Adding More Wires . . . . . . . . . . . . . . . . . . . 13
Push the Button . . . . . . . . . . . . . . . . . . . . . . 14
The Mars Department:
Greenhouses in Space . . . . . . . . . . . . . . . . . . . 15
Water Sensors . . . . . . . . . . . . . . . . . . . . . . . .16
Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Resistors in Parallel . . . . . . . . . . . . . . . . . . . .19
Resistors in Series . . . . . . . . . . . . . . . . . . . . .19
Color-Coded Resistors . . . . . . . . . . . . . . . . . 19
The Uranus Department:
Space Workshop . . . . . . . . . . . . . . . . . . . . . . . 20
Battery Tester . . . . . . . . . . . . . . . . . . . . . . . .21
Polarity Tester . . . . . . . . . . . . . . . . . . . . . . . .22
Transistor Tester . . . . . . . . . . . . . . . . . . . . . .22
Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Sensor Key . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Sensor Key 2 . . . . . . . . . . . . . . . . . . . . . . . . .24
Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Capacitor Experiments . . . . . . . . . . . . . . . . .26
A Timed Blinker . . . . . . . . . . . . . . . . . . . . . . 27
The Venus Department:
Home of the Space Cleaners . . . . . . . . . . . . . .28
Siren Circuit . . . . . . . . . . . . . . . . . . . . . . . . . 29
Heat Sensor . . . . . . . . . . . . . . . . . . . . . . . . . .30
Fuel Gauge Sensor . . . . . . . . . . . . . . . . . . . . 31
The Jupiter Department:
The Heart of the Station . . . . . . . . . . . . . . . . . 32
Double Doorbell . . . . . . . . . . . . . . . . . . . . . .33
Security Light . . . . . . . . . . . . . . . . . . . . . . . . 34
YES Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . .35
NO Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . .35
AND Circuit . . . . . . . . . . . . . . . . . . . . . . . . . .36
OR Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
AND/NOT Circuit . . . . . . . . . . . . . . . . . . . . . .37
OR/NOT Circuit . . . . . . . . . . . . . . . . . . . . . . .37
LED Communicator . . . . . . . . . . . . . . . . . . . 38
Table of Contents
The Neptune Department:
Link to Earth . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Morse Code Device . . . . . . . . . . . . . . . . . . . .40
Earphones and Speakers . . . . . . . . . . . . . . . 41
Fruit Musical Device . . . . . . . . . . . . . . . . . . .42
Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . 43
Water Detector . . . . . . . . . . . . . . . . . . . . . . .43
Sonic Pest Repellent . . . . . . . . . . . . . . . . . . .43
Electronic Horn . . . . . . . . . . . . . . . . . . . . . . .44
The Pluto Department:
Entertainment for Electronica . . . . . . . . . . . . .45
Simple Drum Machine . . . . . . . . . . . . . . . . .46
Trivia Game Timer . . . . . . . . . . . . . . . . . . . . 47
Electronic Snake Charmer . . . . . . . . . . . . . .48
Flip-Flop Switch . . . . . . . . . . . . . . . . . . . . . . 49
Two-Way Switch . . . . . . . . . . . . . . . . . . . . . .50
The Saturn Department:
A Heavenly Amusement Park . . . . . . . . . . . . .51
Go-Cart Siren . . . . . . . . . . . . . . . . . . . . . . . . 52
Lie Detector . . . . . . . . . . . . . . . . . . . . . . . . .52
LED Magic Show . . . . . . . . . . . . . . . . . . . . . .53
LED Switch 1 . . . . . . . . . . . . . . . . . . . . . . . . .54
LED Switch 2 . . . . . . . . . . . . . . . . . . . . . . . . .54
Transistor Switch 1 . . . . . . . . . . . . . . . . . . . .55
Transistor Switch 2 . . . . . . . . . . . . . . . . . . . .55
The Mercury Department:
Space Voltacademy . . . . . . . . . . . . . . . . . . . . . 56
Intruder Alert . . . . . . . . . . . . . . . . . . . . . . . .57
YES Transistor Circuit . . . . . . . . . . . . . . . . . .58
NO Transistor Circuit . . . . . . . . . . . . . . . . . . 58
AND Transistor Circuit . . . . . . . . . . . . . . . . . 59
OR Transistor Circuit . . . . . . . . . . . . . . . . . . .59
AND/NOT with Transistor . . . . . . . . . . . . . . .60
OR/NOT with Transistor . . . . . . . . . . . . . . . .60
Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Germanium Diode . . . . . . . . . . . . . . . . . . . . 61
Diodes in Transistors 1 . . . . . . . . . . . . . . . . .62
Diodes in Transistors 2 . . . . . . . . . . . . . . . . .62
Diodes in Transistors 2 . . . . . . . . . . . . . . . . .63
Diodes in Transistors 2 . . . . . . . . . . . . . . . . .63
Medium Wave Radio . . . . . . . . . . . . . . . . . . 64
Reflex Receiver . . . . . . . . . . . . . . . . . . . . . . .65
Night Falls on Electronica . . . . . . . . . . . . . . 66
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
1

PWM UinPWM
Uin
Multipack 1
000 845
Resistors
10 pieces
various resistance
values
K A
Capacitors
2 x 6 .8 nF
Electrolytic
capacitors
1 x 10 µF
1 x 100 µF
6.8 nF
A K The Components
NTC
CDS
10 µF
220 kΩ
6.8 nF
NTC
10 µF
+
220 kΩ
–
10 10 µF µF
220 220 kΩ kΩ
B
10 µF
220 kΩ
+
B
CDS
Resistors are for adjusting the power and voltage in circuits . The unit for the electric A resistance K is
the ohm (short for Greek omega = Ω) . By putting E “kilo” for thousand” Cor
C “mega” for 10 mF million before
it, you get the abbreviated names for larger resistance values . For example, 1 kΩ = 1 kilo-ohm
= 1000 ohms . The value of the resistance is indicated K Aon
the resistor B in the form of a color code .
B
B
It is usually three colored rings and an additional fourth ring that indicates the tolerance of the
resistor . On the NTC NTC back cover of this manual, you will NTCfind
the entire color code . The abbreviation for
a resistor is the letter “R .” If there are several resistors in a circuit, then Ea
Enumber
is added to their
symbol, resulting in R1, R2, R3, and so on .
CK
A
HS
Germanium diode
NTC
B
A E
DGe
K
A
D DGe Ge Ge
6.8 nF
K
B
C
A
A
NTC
A K
D E F
Diodes allow the electric current to flow only in one direction and stop it in the other . Diodes are M BN
C
ELau
La
auf auf
KK LL
LED
K
used anywhere that this DGe valve effect is needed . The polarity D Ge is designated by the so-called cathode
ring . In forward K L Adirection (the direction K in which AA the BNTC B Ccurrent
C is allowed to pass Athrough, A B C
Potianschlüsse
Cthe
side
A C
with the ring), + there EP has to be more negative potential + than at the anode . Germanium is the semi-
E
+
conductor material in this diode, hence the name . A germanium A K diode offers the
220 auf advantage
kΩ Steckfedern that it D, E und
EP
consumes little voltage . With it, you can build a simple but powerful radio . Lautsprecheranschlüsse
erkanschlüsse
ckfedern kfedern K und L
2
+
Meßwerkanschlüsse –
–
auf Steckfedern M und N
Caution! Never
–
connect the diode Variable directly to capacitor the battery! terminals It could burn Variable through! capacitor terminals
auf Steckfedern K und L
on contact clips B
on contact clips A, B, and C
B
on contact clips A, B, and C
A, B, and C
A B C
A C
TF
C
E
6
6.8 nF
K A
220 kΩ
E C
These capacitors have a large capacity . The unit here is the microfarad (abbrev . µF) . The 10 µF
capacitor, Variable for example, capacitor has about terminals 1470 times the capacity as the 6 .8 nF capacitor . Due to the special
construction with a so-called electrolyte, the electrolytic capacitor B is poled; it is designated with a
on contact clips A, B, and C
B
plus and a minus . So it is important to always pay attention to the polarity when installing it .
C
Warning! Installing electrical components with the wrong polarity can cause damage!
4
B
C
6
E10
10 m
C
E
6.8 6.8 n
E
6.8 nF
220 220k
A capacitor stores an electrical charge and decouples (prevents the unwanted transfer K of A electricity
between) circuit components, since it is impermeable for direct current . However, it allows
alternating current to pass through . Its unit of measure is the farad, abbreviated as “F .” In practice,
however, a farad is much too large, since a millionth, billionth, or even trillionth of a farad Mis N
usually enough for a given DGeapplication
. These very small D units Ge are then referred to as microfarad
A K
(µF), nanofarad (nF), and picofarad (pF) . In Multipack 1 in the kit, there are two 6 .8 220 nF kΩ capacitors .
Sometimes, however, “6800 pF” is printed on these .
A K
C
Lautsprecheranschlüsse
auf Steckfedern M und N
+
B
C
A B C
A C
E
10 mF TF
B
6
1
2
4 3
B
1
6
A
C
CDS
6.8 nF
10 µF
220 kΩ
2
K
Picture Construction
A K B
Wiring Symbol
6
6.8 nF
10 µF
220 kΩ
4
3
C
E
6
AMP
4
E
–
C E
A
K
+ +
C
E
E
V
+
A

A
A
E
A
When current passes through one of these light-emitting diodes, it either emits red or green light,
depending on its semiconductor material . Light-emitting diodes C are also poled C and only allow the
current to pass through in one direction . It is therefore important to pay attention to the correct
+
polarity — the short side is the cathode (–), the long side Bthe
anode (+) B.
A light-emitting diode is
also called an LED for short .
CDS
Caution! Never connect an LED directly to a battery . The light-emitting diode will immediately
burn out! Always use it with a series resistor of at least 470 ohms .
C E
K
The push-button (or “momentary-contact actuator”) is used to create a short-term conductive connection
between two points in a circuit . Using it, one can close an electric circuit and, for example,
make a light-emitting diode light up as long Cas
the push-button is pressed . When it is released, the
connection is interrupted once again . Push-buttons are abbreviated as Pb in this text .
+
B
A K
E
10 mF
6.8 nF
The variable capacitor is affixed to the console using
CDS
the two short screws . Beforehand, however,
the two plastic parts there have to be removed from the console (step 1 on page 8) . The best Mway N
is to twist them until they separate from the Cplastic
DGe console . The DGelong
D screw Ge is used D to Geattach
the
A K A K
rotary knob to the variable capacitor (step 3 on page 8) .
B
A K
A K
K L
Picture Construction Wiring Symbol
6.8 nF
10 µF
220 kΩ
NTC
E
10 µF
K
220 kΩ
The variable capacitor consists of two capacitors of approximately 80 and 150 picofarads . Several
HS
HS
insulated metal plates are simply pressed into each other . A variable capacitor is used to adjust
resonant circuits and is therefore able, for example, to adjust the reception frequency of a radio .
220 kΩ
The variable capacitor has three terminal leads, one for each capacitor, and a joint terminal . The
LED 3
LED 3 A
A
terminal leads O, G, and A of the variable capacitor are connected to contact clips A, B, and C
A K
A K
located beneath the plug-in panel on the electronics console (step 4 on page 8) .
A K
IR-LED
K L
Meßwerkanschlüsse Meßwerkanschlüsse
auf Steckfedern K und auf Steckfedern L K und L
A K
IR-LED
K
+
–
LED
6.8 nF
10 µF
220 kΩ
6
1
NTC
K
A
6.8 nF
10 µF
A
A
K
K
A
6.8 nF
The battery clip is placed into a compartment under the console, its connections are threaded
through and connected to contact clip 404 (red positive terminal) and contact clip 804 (black negative
terminal) (step 5 on page 9) . Then the clip C is connected to a 9-volt battery and it is ready for
operation . Due to its limited shelf life, the 9-volt battery is not included in the kit .
Caution! Never short-circuit the battery, B as it could explode!
+
+ –
A K E 10 mF
A B C
2
EP
B
6 1
4 3
E
C
E
EP
A C
Variable – capacitor terminals Variable capacitor terminals
B
on contact clips A, on B, and contact C clips A, B, and C
K
NTC
+
LED
1
A B C
6
2
EP
2
4 3
B
E
C
E
6
4
3
1
2
A
K
220 kΩ
K
C 2 pieces E
B
Light-emitting
diodes
A 1 x red 000 145
1 x green 002 198
Bag of small
PHT
components O
000 148
Push-button
Screws
3 pieces for the
variable capacitor
000 143
VariableC
capacitor
Potianschlüsse B Potianschlüsse
auf Steckfedern D, auf E und Steckfedern F D, E und F
9-volt
K 9 VA
Ebattery
clip
EP
+ –
M
A
10 mF
6.8 nF
A C
B
C
E
C
042 106
C
O
+
P
NTC
10 kΩ
C E
Lautsprecheranschlüsse Lautsprecheranschlüsse SP
auf Steckfedern M auf und Steckfedern N M und N
B
4
AMP
E
–
3
TF
E C
A
D E F
K
+
10 mF
6.8 nF
220 kΩ
V
AMP
+
E
–
M N
TF
E C
A
V
E
D E F
–
R O
U
S T S
V
+
AMP
P
–
+
E
A
TF
U
S
V
E
O
3
C
C
SP
+
–
+
AMP
P
P
+
NT
+
P
N
+
C
E
P
N

000 144
042 056
K L
L-module
A K
Earphone
npn
Transistor module
2 pieces
043 006
Electronics
console
Upper console part 1
070 207
Lower console part 2
070 407
Plastic caps
and knob
With 2 caps and knob
for variable capacitor
004 012
4
Meßwerkanschlüsse
auf Steckfedern K und L
LED 3
A K
IR-LED
Picture K A Construction Wiring Symbol
Meßwerkanschlüsse Meßwerkanschlüsse –
Variable – capacitor terminals Variable capacitor terminals
auf Steckfedern K und auf LSteckfedern
K und L
B
B
on contact clips A, B, on and contact C clips A, B, and C
6.8 nF
The A L-module K is a Atransformer, K which consists of a coil with two windings around an iron core and
E C
several terminals, called taps . LED It is the counterpart LED
Meßwerkanschlüsse
–
to the capacitor, with which it forms a resonant
A K
A K
Variable capacitor terminals
Potianschlüsse Potia
auf Steckfedern circuit that can be set to a certain K frequency . The EP
IR-LED K und L
K strength of the EPcoil
can be B
IR-LED
on contact clips A, B, and C
adjusted with auf Steckfedern a screw- D, E auf und Steckfe F
EP
EP
driver . When the iron core is HS screwed in, the resonant circuit frequency decreases . The resonant
circuit frequency can be adjusted in two ways, either using the coil or the variable capacitor .
Caution! The core is very easy to break, so do not use force to turn it .
10 µF
B C
p
n
p
E E
With the aid of a coil and a metallic membrane, the earphone converts electrical signals E into audible
tones . In this earphone, the coil acts as a sort of electromagnet to vibrate the membrane to
produce sound . When we produce sounds or listen to the radio in this kit, we will use earphone .
K L
K L
K L
LED 3
LED 3
A K
A K
IR-LED
K L
LED 3
A
K
+
–
LED
+
A
+
A
K
LED
HS
HS
220 kΩ
NTC
+
–
+
6
1
HS
A B C
B C
n
p
n
E E
A B CA
C
EP
B
B
C Potianschlüsse
auf Steckfedern D, E und auf F
The transistor module has an npn transistor soldered onto the small circuit board that has four terminals
. Terminal E (emitter) of the transistor, which only has three terminals itself, is represented
twice . There are only one each of the other two terminals B (base) and C (collector) . To put it very
simply, imagine that a transistor is an adjustable resistor; the resistor between the collector and
emitter terminals can be adjusted using the base terminal . In a way, the base terminal is therefore
the control dial that one turns in order to change the resistance . Of course, one doesn’t actually
turn a knob by hand in this case, but rather by using electric currents!
2
4 3
6
1
1
6
2
2
4 3
Join the upper and lower console pieces together
by inserting the two caps in the holes on
the sides . The caps then form a hinge, so that
the console can be opened and closed . Insert
the contact clips into the many rectangular
recesses on the console until they click audibly
into place . This area is called the plug-in panel .
Please follow the component mounting diagram
(step 2 on page 8)!
The two upper rows (contacts 200 to 204 and
300 to 304) are left open .
The caps are used to connect the upper and
lower console parts .
The rotary knob is affixed to the axis of the
variable capacitor using the long screw from
the bag of small parts . To do this, first turn the
variable capacitor DGecompletely
to the left . Then D Ge
A K
place the knob with the indicator mark pointing
to the left onto the variable capacitor, Aand
K
then screw it in .
A B C
4
on A contact A B clips C A, B, and CA
C
6
1
DGe
A B C
A K
Variable capacitor terminals
6
1
2
EP
2
4 3
EP
6
4 3
1
2
EP
A
D Ge
1
K
6
4
3 1
6
2
3
2
A
A C
C
E
K
A C
B
3
E –
4
AMP
TF
E C
A
D E F
TF
V
+
A
K L
C
AMP
E –
Lautsprecheranschlüsse
auf Steckfedern M und N
4
AMP
E
3
–
M N
A
D E F
V
+
La
E auf
AMP

A
K
The contact sleeves are used to connect the extension wires to the terminals of the light-emitting
diodes when you want to install them in the console to the left next to the variable capacitor .
One of the terminal leads of a light-emitting Cdiode and E one extension wire are inserted into one
contact sleeve; the contact sleeve becomes narrower on the inside and thus clamps the two wires
together . Then, the wire is bent downward and the light-emitting diode assembly is finished (see
step 7 on page 9) .
C
C E
6.8 nF
10 µF
The already-bent jumper wires are not enough for some experiments . Longer pieces of wire are
additionally needed . For connecting the light-emitting diodes as well, when they are to be mount-
C
ed in the console, they are needed to extend the connectors .
B
Instruction manual for Electronics Workshop 1
220 kΩ
K
NTC CDS
GND
+9V
D0
D
+5V...+9V
D
A
A K
The short jumper wires have to be bent so that they measure 15 mm (step 8 on page 9) . They make
the electrical connections between the individual contact clips .
C
K
6.8 nF
10 µF
220 kΩ
A
B
D
Picture Construction Wiring Symbol
K
6.8 nF
10 µF
6.8 nF
10 µF
220 kΩ
GND
Digi
PWM Uin
D0 Din
D1 Beep
D2 Start
D3 Reset
D4 +5V
D5 GND
B C
p
n
p
E E
The contact clips are used to hold and connect components and wires on the console . They provide
physical support and electrically connect the components at the same time . The contact clips are
inserted into the rectangular A recesses K of the experiment console until they click audibly into place .
Please follow the component mounting diagram (step 2 on page 8) . The two upper Crows
(contacts
CDS 200 to 204 and 300 to 304) are left open .
C
B
B
B
220 kΩ
NTC
+
A
K
6.8 nF
10 µF
B C
n
p
n
E E
220 kΩ
NTC
The long jumper wires have to be bent so that they measure 30 mm (step 8 on page 9) . They make
the electrical connections between the individual contact clips .
A
B C
p
n
p
E E
B C
n
p
n
E E
E C 10 mF
DGe
A K
C
A B C
B
B
B
E
E
E
E
K
+
B
A
D Ge
A
Contact sleeves
6 pieces in kit
000 612
Contact clips
+
K
33 pieces in bag
000 612
Short jumper
E
wires 10 mF
10 pieces in bag
000 282
Long jumper220
A kΩK
wires
10 pieces in bag
000 292
Wire pieces220
kΩ
E
A K
10 mF
Lautsprec
auf Steckf
K L
A C
C
C
E
3 pieces in bundle
300 mm
000 151
704 920
Instruction
manual
K
10 mF
+
6.8 nF
K
+
K
A
A
6.8 nF
5
A

The Neptune Department:
learned quite a lot from you,” Robert
thanks Julius Delta . And Armstrong
also says goodbye . They can still hear
“I’ve
Delta’s booming voice thanking them as
the first control room door closes .
“Now I’m curious,” says Robert M-3, “about
what comes next .”
“You’ll be surprised to learn that we’ve just
completed half of our tour,” Armstrong tells his
assistant . On their way back to the ring, Robert
sees the next department from the outside
through the window . Many antennas of all imaginable
shapes are mounted there . Some protrude
deeply into space, while others look like giant
butterflies with their wings, and yet others have a
shape similar to a large salad bowl .
“Now I understand,” thinks Robert, “where
the expression ‘jumbled frequencies’ comes from .”
“Here on Electronica,” says the professor as he
begins his discourse, “the Neptune Department is
responsible…”
“ . . .for the radio communications,” says Robert,
finishing Armstrong’s sentence out loud .
“Oh, you already saw the antennas,” replies
the professor with a smile, “And I thought you
were pulling my leg again .”
As they approach the door, Robert asks: “These
radio guys, do they make do without gravity?”
The professor understands the polite reference
to his clumsiness: “Gravity is not absolutely
necessary here, and by the way, you’re going to be
surprised about ‘the radio guys .’”
While Robert is still ruminating about the professor’s
last sentence, they enter the radio department
. “As you’ll see, it looks very similar to the
Jupiter Department here,” the professor explains .
“It’s just a bit noisier, if I can judge by my sensors,”
Link to Earth
replies Robert as he rolls by, for a clamor of beeps
and humming accompanies the glow of LEDs .
Robert sees only people with headphones
sitting in front of the radio computers . “Do just
women work here?” he asks the professor .
“I told you that you were going to be surprised,”
Armstrong says, “and that’s right: This
department is operated solely by women .”
Robert is a little surprised: “Is that so?”
Before the professor is able to answer, a voice
from far away replies: “You bet it is, my little tin
roller!” A small, wiry woman is walking toward
them . She greets the professor amicably: “Howdy,
dear old Sirius!”
“Good afternoon,” Armstrong replies, “I’d like
to introduce you: Ruth Frequency, the director of
the radio department, and this here is my new colleague
Robert M-3 .”
Ms . Frequency looks the new model of robot
up and down: “Pretty impressive, this new series,
but obviously programmed by old engineers on
Earth who don’t know how we do things up here
on Electronica, if you ask me .”
Armstrong apologizes for his assistant, “He
just doesn’t know his way around yet; it’ll take
a little time before his experience memory is
full enough, otherwise he would have naturally
already known a long time ago that the Neptune
Department is one of the most efficient ones here
on Electronica .”
Robert whirrs quietly in embarrassment . But
Ruth Frequency doesn’t hold it against the young
robot . She invites both of them on a tour . “Did
you remember my collection this time?” she asks
the professor along the way .
“Of course I did,” he says, and he explains to
Robert: “Ruth is a passionate collector of antique
radio equipment .”
39

40
Morse Code Device
The professor digs a device out of his seemingly
inexhaustible bag that does in fact look as if it is
a few dozen years old . Ms . Frequency examines
the fine piece from all sides with the look of a
connoisseur . “This is — no, it can’t be!” she says
enthusiastically, “this is a Morse device from the
early 20th century!”
“It sure is,” Armstrong confirms, “and the
funny thing is: it still works!”
That’s the signal for Robert: “May I try the
thing out? I’ll certainly be very careful with it .”
Ruth is a bit hesitant, but says, “Well, I suppose,
since it’s you .”
M-3 takes the Morse device — and just then it
slips out of his fingers .”
“Lucky there’s no gravity here,” says Armstrong,
relieved . Only a couple of components
have slipped out of their contact clips .
“I brought the circuit diagram along with me,
anyway .”
experiment_82
He assembles the parts according to the diagram
shown below . The professor immediately tests
whether or not it emits the characteristic tones .
He holds down the button . A long tone sounds; he
presses it quickly, and a short tone can be heard .
“With long tones (they are written as a dash)
and short tones (written as a dot),” Ms . Frequency
explains, “you can send information . For this,
radio operators used to use the ‘Morse alphabet’:
each letter of the alphabet is assigned a very
specific sequence of dots and dashes . Incidentally,
this was invented by American researcher Samuel
Morse who lived from 1791 to 1872 .”
“This,” says Armstrong as he pulls out a piece
of paper, “is what the Morse alphabet looked
like .” It is printed below .
“By the way, my dear Ruth,” offers the professor,
“if the tone in the earphone is too shrill, a
small adjustment is enough to make it more pleasant
.”
experiment_83
He removes the 33 kΩ resistor (orange-orangeorange)
from the circuit and puts a 220 kΩ resistor
(red-red-yellow) in its place . And the tone that
sounds after pressing the button is in fact lower
than before .
“For my sensitive ears,” Ruth complains, “even
this tone is still too high .“ Armstrong knows how
to take care of it .
experiment_84
For R2, he now installs a 680 kΩ resistor (bluegray-yellow)
into the circuit .
As can be expected, the professor is right: The
tone really is even lower .
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
1
2
3
4
5
6
7
8
9
0

54
LED Switch 1
LED Switch 2
LED 1 = Red
LED 2 = Green
LED 1 = Red
LED 2 = Green
“I actually have something even cooler up my
sleeve,” says Pokus .
“Then what are we waiting for?” the curious
robot urges .
experiment_124
Pokus puts this assembly together as well . It looks
like in the drawing above .
After inserting jumper wire S, the green LED
lights up, but the red one remains off . As soon as
Robert presses the button, the green diode goes
off, but the red one comes on .
“I can explain that myself,” says Robert: “As
long as Pb1 is open, the current flows exclusively
through the green diode and makes it light up . If
I connect Pb1, then there is a flowing of current,
around the green diode, and through the button
“Red and green LEDs are my weakness,“ confesses
Hokus Pokus the magician, “which is why I’ve
developed a large series of circuits with which you
can turn them on and off .“
“Could you maybe show us a couple of them?”
asks Robert .
experiment_123
“No problem at all,” replies Pokus and constructs
a circuit according to the illustration to the left .
If no button is pressed, then both diodes light up .
Pressing on Pb2 makes the green diode go off,
while pressing Pb1 has the same effect on the red
one . If both buttons are pressed, then the magic
with the colors is over: both diodes are extinguished
.
“The explanation for this is quite simple,” the
magician says: “With the push of a button, the
respective current flows through the button —
around the diode, in a manner of speaking .”
and the red LED, which lights up as a result . The
reason why the current prefers to flow through
the red LED rather than through the green one
must be because the serial connection consisting
of R1, 150 Ω (brown-green-brown), and the green
LED has a higher ‘innate resistance’ than the red
LED .”
Pokus confirms Robert’s explanation .

“Then let’s tackle something simpler,” suggests
Armstrong, “and talk about a component that
we’ve been using all the time but about whose
function we haven’t thought about at all: the
diode . The diode’s function is to allow the current
to pass in one direction but to block it in the other
direction .”
During this discourse, Wave has made two drawings
on the board: “Think of the diode as being
like this gate . As can be seen clearly in the upper
picture, the water is blocked from K to A; the
lower picture shows that the water is able to flow
unimpeded from A to K .”
“But up to now we haven’t even noticed that
the light-emitting diode is even blocking current!”
it occurs to Robert .
“That is simply because we have always used
them in the ‘conductive direction,’” Armstrong
notes . “Is a little experiment in order?”
“Not all diodes light up,” says Wave . “For example,
this here is a germanium diode . It also blocks
the current in one direction, but doesn’t indicate
that current is flowing in the other direction by
lighting up .”
experiment_137
In order to test whether germanium diode D1 is
actually living up to expectations, Wave puts the
assembly together as shown to the right .
The light-emitting diode lights up and thus
tells us that the germanium diode is placed in the
forward direction .
experiment_138
Robert now removes the germanium diode and
sticks it in again, this time in the other direction .
Here as well, the result of the experiment comes
as no surprise . The germanium diode blocks the
current, and the light-emitting diode remains
dark .
experiment_135
He puts the demonstration circuit together according
to the figure above .
“It makes sense, of course, that the diode
lights up, because it is mounted in the forward
direction and allows the current to flow through
it,” recognizes Siegfried immediately .
Now he removes the diode and puts it back in
place but ‘the wrong way around .’
experiment_136
As can be expected, nothing happens in the lightemitting
diode, because it is blocking the current .
Diodes
The housing of the
light-emitting diode is
flattened on one side.
This flattened area is
represented by the
crossbar in the circuit
symbol. Experts call
this side the “cathode”
and often abbreviate this
word as “K.” A diode
always has a blocking
effect when the cathode
lies in the direction of
the positive pole of the
battery. Accordingly, it is
conductive when it points
toward the negative pole.
Germanium Diode
The cathode of the germanium diode
is indicated by a black ring on its glass
body. This means that it blocks current
when the black ring is facing toward the
positive pole.
61