Elenco Electronics SC-300 User manual

SNAP CIRCUITSTM
Projects 102-305
Instruction Manual
REV-B Revised 2002

ADDITIONAL PARTS LIST (Colors and styles may vary) Symbols and Numbers
-1-
Qty. ID Name Symbol Part # Qty. ID Name Symbol Part #
31-Snap Wire 6SC30001 110µF Capacitor 6SC30032
32-Snap Wire 6SC30002 1100µF Capacitor 6SC30033
13-Snap Wire 6SC30003 1470µF Capacitor 6SC30034
14-Snap Wire 6SC30004 11kΩResistor 6SC30041
17-Snap Wire 6SC30007 15.1kΩResistor 6SC30042
1Battery Holder - uses
2 1.5V type AA (not Included)
6SC30019 110kΩResistor 6SC30043
1Antenna Coil 6SC30025 1100kΩResistor 6SC30044
1Green Light Emitting
Diode (LED) 6SC30026 1High Frequency Integrated Circuit 6SC30045
16V Lamp Socket
6V Bulb (6.2V, 0.5A)
Type 425 or similar
6SC30027
6SC30027B 1PNP Transistor 6SC30051
1Microphone 6SC30028 1NPN Transistor 6SC30052
1Power Amplifier
Integrated Circuit 6SC30029 1Adjustable Resistor 6SC30053
10.02µF Capacitor 6SC30030 1Variable Capacitor 6SC30054
10.1µF Capacitor 6SC30031
D2
A1
B1
7
4
3
2
1
L2
X1
U4
C1
C2
U5
R5
R4
R3
R2
C5
C4
C3
Q1
Q2
RV
CV

The Electronic Snap Circuit Kit has 204 projects. They are simple to build and
understand.
The snap circuit kit uses building blocks with snaps to build the different
electrical and electronic circuits in the projects. Each block has a function:
there are switch blocks, lamp blocks, battery blocks, different length wire
blocks, etc. These blocks are in different colors and have numbers on them
so that you can easily identify them. The circuit you will build is shown in color
and numbers, identifying the blocks that you will use and snap together to
form a circuit.
For Example:
This is the switch block which is green and has the marking on it.
This is a wire block which is blue and comes in different wire lengths.
This one has the number , , , , , or on it depending on the
length of the wire connection required.
There is also a 1-snap wire that is used as a spacer or for interconnection
between different layers.
To build each circuit, you will have two (2) power source blocks marked
that need two (2) “AA” batteries each (not included with the snap circuit kit).
A large clear plastic base grid is included with this kit to help keep the circuit
block together. You will see evenly spaced posts that the different blocks snap
into. You do not need this base to build your circuits, but it does help in
keeping your circuit together neatly. The base has rows labeled A-G and
columns labeled 1-10.
Next to each part in every circuit drawing is a small number in black. This tells
you which level the component is placed at. Place all parts on level 1 first,
then all of the parts on level 2, then all of the parts on level 3, etc.
The 2.5V bulb comes packaged separate from its socket. Install the bulb in
the lamp socket whenever that part is used. Do the same for the 6V bulb
and socket .
Place the fan on the motor whenever that part is used, unless the project
you are building says not to use it.
Some circuits use the jumper wires to make unusual connections. Just clip
them to the metal snaps or as indicated.
Note: While building the projects, be careful not to accidentally make a direct
connection across the battery holder (a “short circuit”), as this will damage
and/or quickly drain the batteries.
CreatingYour Own Circuits
After building the circuits given in this booklet, you may wish to experiment on
your own. Use the projects in this booklet as a guide, as many important
design concepts are introduced throughout them. Every circuit will include a
power source (the batteries), a resistance (which might be a resistor, lamp,
motor, integrated circuit, etc.), and wiring paths between them and back. You
must be careful not to create "short circuits" (very low-resistance paths across
the batteries) as this will damage components and/or quickly drain your
batteries. Only connect the ICs using configurations given in the projects,
incorrectly doing so may damage them. Elenco™ Electronics is not
responsible for parts damaged due to incorrect wiring.
For all of the projects given in this book, the parts may be arranged in different
ways without changing the circuit. For example, the order of parts connected
in series or in parallel does not matter — what matters is how combinations
of these sub-circuits are arranged together.
You are encouraged to tell us about new circuits you create. Upon review, we
will post them with your name, age, and hometown in a special section on our
website.
Troubleshooting
Most circuit problems are due to incorrect assembly, always double-check that
your circuit exactly matches the drawing for it. Be sure that parts with
positive/negative markings are positioned as per the drawing. Sometimes the
light bulbs come loose, tighten them as needed. Try replacing the batteries.
-2-
HOW TO USE IT
S1
OFF ON
B1
2 3 4 5 67
L1
L2
M1

-3-
Project # Description Page #
102 Batteries in Series 5
103 Batteries in Parallel 5
104 Spacey Fan 6
105 Two-Transistor Light Alarm 6
106 Light-Controlled Alarm 6
107 Automatic Street Lamp 7
108 Voice-Controlled Rays of Light 7
109 Blowing Off the Electric Light 7
110 Adjustable Tone Generator 8
111 Photosensitive Electronic Organ 8
112 Electronic Cicada 8
113 Light & Sounds 9
114 More Light & Sounds 9
115 More Light & Sounds (II) 9
116 More Light & Sounds (III) 9
117 More Light & Sounds (IV) 9
118 Motor Speed Detector 10
119 Old-Style Typewriter 10
120 Space War Sounds 11
121
Space War Sounds Controlled by Light 11
122 Space War Radio 12
123 The Lie Detector 12
124 NPN Amplifier 13
125 PNP Amplifier 13
126 Sucking Fan 14
127 Blowing Fan 14
128 PNP Collector 14
129 PNP Emitter 14
130 NPN Collector 15
131 NPN Emitter 15
132 NPN Collector - Motor 15
133 NPN Emitter - Motor 15
134 Buzzing in the Dark 16
135 Touch Buzzer 16
Project # Description Page #
136
High Frequency Touch Buzzer
16
137
High Frequency Water Buzzer 16
138 Mosquito 16
139 High Sensitivity Voice Doorbell 17
140 Louder Doorbell 17
141 Very Loud Doorbell 17
142 Doorbell with Button 17
143 Darkness Announcer 17
144 Musical Motion Detector 17
145 Radio Music Alarm 18
146 Daylight Music Radio 18
147 Night Music Radio 18
148 Night Gun Radio 18
149 Radio Gun Alarm 18
150 Daylight Gun Radio 18
151 Blow Off a Space War 19
152 Series Lamps 19
153 Parallel Lamps 19
154 Fire Fan Symphony 20
155 Fire Fan Symphony (II) 20
156 Fan Symphony 20
157 Fan Symphony (II) 20
158 Police Car Symphony 21
159 Police Car Symphony (II) 21
160 Ambulance Symphony 21
161 Ambulance Symphony (II) 21
162 Static Symphony 22
163 Static Symphony (II) 22
164 High-Power Symphony 22
165 High-Power Symphony (II) 22
166 Water Detector 23
167 Salt Water Detector 23
168 NPN Light Control 24
169 NPN Dark Control 24
Project # Description Page #
170 PNP Light Control 24
171 PNP Dark Control 24
172 Red & Green 25
173 Current Limiters 25
174 Current Equalizing 25
175 Battery Polarity Tester 25
176 Blow Off a Doorbell 26
177 Blow Off a Candle 26
178 Blow On a Doorbell 26
179 Blow On a Candle 26
180 Screaming Fan 27
181 Whining Fan 27
182 Light Whining 27
183 More Light Whining 27
184 Motor Than Won’t Start 27
185 Whiner 28
186 Lower Pitch Whiner 28
187 Hummer 28
188 Adjustable Metronome 28
189 Quiet Flasher 28
190 Hissing Foghorn 29
191 Hissing & Clicking 29
192 Video Game Engine Sound 29
193 Light Alarm 30
194 Brighter Light Alarm 30
195 Lazy Fan 30
196 Laser Light 30
197 Water Alarm 31
198 Drawing Resistors 31
199 Pitch 32
200 Pitch (II) 32
201 Pitch (III) 32
202 Flooding Alarm 32
203 MakeYour Own Battery 33
PROJECT LISTINGS

-4-
PROJECT LISTINGS
Project # Description Page #
204 MakeYour Own Battery (II) 33
205 MakeYour Own Battery (III) 33
206 Tone Generator 34
207 Tone Generator (II) 34
208 Tone Generator (III) 34
209 Tone Generator (IV) 34
210 More Tone Generator 35
211 More Tone Generator (II) 35
212 More Tone Generator (III) 35
213 Music Radio Station 36
214 Alarm Radio Station 36
215 Saved Electricity 36
216 Motor & Lamp by Sound 37
217 Fading Siren 37
218 Fast Fade Siren 37
219 Laser Gun with Limited Shots 38
220 Symphony of Sounds 38
221 Symphony of Sounds (II) 38
222 Transistor Amplifiers 39
223 Pressure Meter 39
224 Resistance Meter 39
225 Auto-Off Night-Light 40
226 Discharging Caps 40
227 Changing Delay Time 40
228 Morse Code Generator 41
229 LED Code Teacher 41
230 Ghost Shriek Machine 41
231 LED & Speaker 41
232 Dog Whistle 41
233 Electronic Golf Game 42
234 Enhanced Quiet Zone Game 43
235 Capacitor Charge & Discharge 43
236 Sound Wave Magic 44
237 Space War Amplifier 44
Project # Description Page #
238 Trombone 45
239 Race Car Engine 45
240 Power Amp 46
241 Electronic Kazoo 46
242 AM Radio 47
243 Fire Engine Symphony 48
244 Fire Engine Symphony (II) 48
245 Vibration or Sound Indicator 48
246 Two-Finger Touch Lamp 49
247 One-Finger Touch Lamp 49
248 Space Battle 50
249 Space Battle (II) 50
250 Multi-Speed Light Fan 50
251 Light & Finger Light 50
252 Storing Electricity 51
253 Lamp Brightness Control 51
254 Electric Fan 51
255 Radio Music Burglar Alarm 52
256 Light Dimmer 52
257 Motion Detector 53
258 Fan Modulator 53
259 Oscillator 0.5 - 30Hz 54
260 Sound Pulse Oscillator 54
261 Motion Detector (II) 54
262 Motor Rotation 55
263 Motor Delay Fan 55
264 Motor Delay Fan (II) 55
265 High Pitch Bell 56
266 Steamboat Whistle 56
267 Steamship 56
268 Steamship Horn 56
269 Noise-Activated Burglar Alarm 57
270 Motor-Activated Burglar Alarm 57
271 Light-Activated Burglar Alarm 57
Project # Description Page #
272 Optocoupler with LED 58
273 Optocoupler with Speaker 58
274 Pressure Alarm 59
275 Power Microphone 59
276 LED Fan Rotation Indicator 60
277 Space War Sounds with LED 60
278 Sound Mixer 61
279 Sound Mixer Fan Driver 61
280 Electric Fan Stopped by Light 62
281 Motor & Lamp 62
282 Start-Stop Delay 63
283 Mail Notifying System 63
284 Mail Notifying Electronic Bell 64
285 Mail Notifying Electronic Fan 64
286 Twice-Amplified Oscillator 64
287 Quick Flicking LED 64
288 AM Radio with Transistors 65
289 AM Radio (II) 65
290 Music Amplifier 66
291 Delayed Action Lamp 66
292 Delayed Action Fan 66
293 Police Siren Amplifier 67
294 Lasting Doorbell 67
295 Lasting Clicking 67
296 Leaky Capacitor 68
297 Transistor Fading Siren 68
298 Fading Doorbell 68
299 Blowing Space War Sounds 69
300 Adjustable Time Delay Lamp 69
301 Adjustable Time Delay Fan 69
302
Adjustable Time Delay Lamp (II) 70
303 Adjustable Time Delay Fan (II) 70
304 Watch Light 70
305 Delayed Bedside Fan 70

-5-
Project #102 OBJECTIVE: To show the increase in voltage when
When you close the slide switch (S1), current flows from the batteries
through the slide switch (S1), the 1kΩresistor (R1), the LED (D1),
through the LED (D2), and back to the second group of batteries (B1).
Notice how both LEDs are lit. The voltage is high enough to turn on
both LEDs when the batteries are connected in series. If only one set
of batteries is used, the LEDs will not light up.
Some devices use only one 1.5 volt battery, but they make hundreds
of volts electronically from this small source. A flash camera is an
example of this.
Batteries in Series
Project #103 OBJECTIVE: To show how batteries in parallel are
Build the circuit shown on the left by placing all of the parts with a black
1 next to them on the board first. Then, assemble the parts marked with
a 2 (including the 1-snap wire at base grid location C5). Finally, place a
2-snap wire at grid location C4, leaving the other end of it unconnected as
shown.
The light should be on and the brightness of the lamp will depend on the
quality of the batteries in the holder on the left. Put weak batteries in the
left holder and strong batteries in the right holder. Snap in the loose end
of the 2-snap wire to grid point C5. Now the lamp will get brighter as the
fresh batteries take over and supply the current to the light.
Batteries are placed in parallel when the voltage is adequate but the load
needs more current than one group of batteries can supply. Think of each
battery as a storage tank that supplies water. If you put two in parallel, you
can get more water (current), but the pressure (voltage) stays the same.
Batteries in Parallel

-6-
Project #104 Spacey Fan
OBJECTIVE: To build a fan with space war sounds that
Place the fan onto the motor.
Space war sounds are heard if
light shines on the
photosensitive resistor OR if you
press the press switch (S2), the
fan may start to spin, but will only
get to high speed if you do
BOTH. Try various combinations
of shining light and holding down
the press switch.
Project #106
OBJECTIVE: To show how light is used to turn an
The alarm will sound, as long as light is present. Slowly cover the
photosensitive resistor (RP), and the volume goes down. If you turn
off the lights, the alarm will stop. The amount of light changes the
resistance of the photosensitive resistor (less light means more
resistance). The photosensitive resistor and transistor (Q2) act like a
dimmer switch, adjusting the voltage applied to the alarm.
This type of circuit is used in alarm systems to detect light. If an
intruder turned on a light or hit the sensor with a flashlight beam, the
alarm would trigger and probably force the intruder to leave.
Light-Controlled Alarm
Project #105
Two-Transistor Light Alarm
This light alarm circuit uses two
(2) transistors and both sets of
batteries. Build the circuit with
the jumper connected as shown,
and turn it on. Nothing happens.
Break the jumper connection
and the light turns on. You could
replace the jumper with a longer
wire and run it across a doorway
to signal an alarm when
someone enters.

-7-
Project #107
OBJECTIVE: To show how light is used to control a
Press the press switch (S2) on and set the adjustable resistor (RV) so
the lamp just lights. Slowly cover the photosensitive resistor (RP) and
the lamp brightens. If you place more light at the photosensitive
resistor the light dims.
This is an automatic street lamp that you can turn on by a certain
darkness and turn off by a certain brightness. This type of circuit is
installed on many outside lights and forces them to turn off and save
electricity. They also come on when needed for safety.
Automatic Street Lamp
Project #108
Voice-Controlled Rays of Light
Turn the slide switch
(S1) on. There will be
only a weak light
emitting from the green
LED. By blowing on
the mic (X1) or putting
it near a radio or TV
set, the green LED will
emit light, and its
brightness changes as
the loudness changes.
Project #109
Blowing Off the Electric Light
Install the parts. The
lamp (L1) will be on. It
will be off as long as
you blow on the mic
(X1). Speaking loud
into the mic will
change the brightness
of the lamp.

-8-
Project #110
OBJECTIVE: To show how resistor values change the
Turn on the slide switch (S1), the speaker (SP) will sound and the LED
(D2) will light. Adjust the resistor (RV) to make different tones. In an
oscillator circuit, changing the values of resistors or capacitors can
vary the output tone or pitch.
Adjustable Tone Generator
OBJECTIVE: To show how resistor values change the
Project #112
Electronic Cicada
OBJECTIVE: To show how capacitors in parallel
Use the circuit from Project 110 shown above, replace the
photosensitive resistor (RP) back to the 100kΩ(R5) resistor. Place the
0.02µF (C1) on top of the whistle chip (WC). Place the slide switch (S1)
on and adjust the resistor (RV). The circuit produces the sound of the
cicada insect. By placing the 0.02µF on top of the whistle chip, the
circuit oscillates at a lower frequency. Notice that the LED flashes also
at the same frequency.
It is possible to pick resistors and capacitors that will make the pitch
higher than humans can hear. Many animals, however, can hear these
tones. For example, a parakeet can hear tones up to 50,000 cycles per
second, but a human can only hear to 20,000.
Use the circuit from Project 110 shown above. Replace the 100kΩ(R5)
with the photosensitive resistor (RP). Turn on the slide switch (S1). The
speaker (SP) will sound and the LED (D2) will light. Move your hand up
and down over the photosensitive resistor (RP) and the frequency
changes. Decreasing the light on the photosensitive resistor increases
the resistance and causes the circuit to oscillate at a lower frequency.
Notice that the LED flashes also at the same frequency as the sound.
By using your finger, see if you can vary the sounds enough to make this
circuit sound like an organ playing.
Project #111
Photosensitive Electronic Organ

-9-
Turn on the slide switch (S1). A police siren is heard and the lamp
lights.
Project #114
More Light &
Sounds
OBJECTIVE: To show a
variation of the circuit in
Modify the last circuit by
connecting points X and Y. The
circuit works the same way but
now it sounds like a machine
gun.
OBJECTIVE: To show a
variation of the circuit in
Project #116
More Light &
Sounds (III)
OBJECTIVE: To show a
variation of the circuit in
Project #117
More Light &
Sounds (IV)
OBJECTIVE: To show a
variation of the circuit in
Project #113 Light & Sounds
Project #115
More Light &
Sounds (II)
Now remove the connection
between X and Y and then make
a connection between T and U.
Now it sounds like a fire engine.
Now remove the connection
between T and U and then make
a connection between U and Z.
Now it sounds like an ambulance.
Now remove the connections
between U and Z and between V
and W, then make a connection
between T and U. Now it sounds
like a water faucet.

-10-
Project #118
OBJECTIVE: To show how to make electricity in one
When building the circuit, be sure to position the motor with the
positive (+) side snapped to the 470µF capacitor (C5). Turn on the
slide switch (S1), nothing will happen. It is a motor speed detector,
and the motor isn't moving. Watch the LED (D2) and give the motor a
good spin CLOCKWISE with your fingers (don't use the fan blade);you
should see a flash of light. The faster you spin the motor, the brighter
the flash will be. As a game, see who can make the brightest flash.
Now try spinning the motor in the opposite direction (counter-
clockwise) and see how bright the flash is — it won't flash at all
because the electricity it produces, flows in the wrong direction and
won't activate the diode. Flip the motor around (positive (+) side
snapped to the 3-snap wire) and try again. Now the diode lights only
if you spin the motor counter-clockwise.
Motor Speed Detector
Project #119
Turn on the slide switch (S1), nothing will happen. Turn the motor
slowly with your fingers (don’t use the fan blade), you will hear a
clicking that sounds like an old-time manual typewriter keystrokes.
Spin the motor faster and the clicking speeds up accordingly.
This circuit works the same if you spin the motor in either direction
(unlike the Motor Speed Detector project).
By spinning the motor with your fingers, the physical effort you exert is
converted into electricity. In electric power plants, steam is used to
spin large motors like this, and the electricity produced is used to run
everything in your town.
Old-Style Typewriter

-11-
Project #120
OBJECTIVE: To build a circuit that produces multiple
Set the slide switch (S1) to the OFF position. Press the press switch
(S2) down and a space sound will be played. If you hold the press
switch down the sound repeats. Press the press switch again and a
different sound is played. Keep pressing the
press switch to hear all
the different sounds.
Next, set the slide switch (S1) to ON position. One of the sounds will
be played continuously. Turn the switch off and then back on. A
different sound is played. Keep pressing the press switch to hear all
the different combinations of sounds.
The space war integrated circuit has “logic” built into its circuitry that
allows it to switch between many different sounds.
Space War Sounds
Project #121
OBJECTIVE: To change the sounds of a multiple space
Modify the preceding circuit to look like the one shown on the left.
The space war IC (U3) will play a sound continuously. Block the light
from the photosensitive resistor (RP) with your hand. The sound will
stop. Remove your hand and a different sound is played. Wave your
hand over the photosensitive resistor to hear all the different sounds.
Press the press switch down and now two space war sounds are
played. If you hold the press switch down the sound repeats. Press
the press switch again and a different sound is played. Keep pressing
the press switch to hear all the different combinations of sounds.
Space War Sounds Controlled By Light

-12-
Project #122
OBJECTIVE: To transmit Space War sounds to a AM
Place the circuit next to an AM radio. Tune the radio so no stations are
heard and turn on the slide switch (S1). You should hear the space war
sounds on the radio. The red LED should also be lit. Adjust the
variable capacitor (CV) for the loudest signal.
You have just performed the experiment that took Marconi (who
invented the radio) a lifetime to invent. The technology of radio
transmission has expanded to the point that we take it for granted.
There was a time, however, when news was only spread by word of
mouth.
Space War Radio
Project #123
OBJECTIVE: To show how sweat makes a better
Turn on the slide switch (S1) and place your finger across point A and
B. The speaker will output a tone and the LED will flash at the same
frequency. Your finger acts as a conductor connecting points A and B.
When a person is lying, one thing the body starts to do is sweat. The
sweat makes the finger a better conductor by reducing its resistance.
As the resistance drops, the frequency of the tone increases. Lightly
wet your finger and place it across the two points again. Both the
output tone and LED flashing frequency increase. Now change the
wetness of your finger by drying it and see how it affects the circuit.
This is the same principle used in lie detectors that are sold
commercially.
The Lie Detector

-13-
Project #124
There are three connection points on an NPN transistor, called base
(marked B), emitter (marked E), and collector (marked C). When a
small electric current flows from the base to the emitter, a larger
(amplified) current will flow from the collector to the emitter. Build the
circuit and slowly move up the adjustable resistor control. When the
LED becomes bright, the lamp will also turn on and will be much
brighter.
NPN Amplifier
Project #125
The PNP transistor is similar to the NPN transistor in Project 166
except that the electric currents flow in the opposite directions. When
a small electric current flows from the emitter to the base, a larger
(amplified) current will flow from the emitter to the collector. Build the
circuit and slowly move up the adjustable resistor control. When the
LED becomes bright, the lamp will also turn on and will be much
brighter.
PNP Amplifier

-14-
Project #126 Sucking Fan
Project #128 PNP Collector
OBJECTIVE: To
demonstrate adjusting
the gain of a transistor
OBJECTIVE: To build a fan
Modify the circuit from Project 126 by
reversing the position of the motor (so
the positive (+) side is towards the
PNP (Q1). Turn it on, and set the
adjustable resistor for the fan speed
you like best. Set it for full speed and
see if the fan flies off - it won’t! The
fan is blowing air upward now! Try
holding a piece of paper just above
the fan to prove this.
Project #127
Blowing Fan
Project #129
PNP Emitter
OBJECTIVE:
To compare
Compare this circuit to
that in Project 128. The
maximum lamp
brightness is less here
because the lamp
resistance reduces the
emitter-base current,
which contacts the
emitter-collector current
(as per Project 25). The
point on the PNP that
the lamp is now
connected to (grid point
C4) is called the emitter.
Build the circuit, and be sure to orient the motor with
the positive (+) side down as shown. Turn it on, and set
the adjustable resistor for the fan speed you like best.
If you set the speed too fast then the fan may fly off the
motor. Due to the shape of the fan blades and the
direction the motor spins, air is sucked into the fan and
towards the motor. Try holding a piece of paper just
above the fan to prove this. If this suction is strong
enough then it can lift the fan blades, just like in a
helicopter.
The fan will not move on all settings of the resistor,
because the resistance is too high to overcome friction
in the motor.
Build the circuit and vary
the lamp brightness with
the adjustable resistor, it
will be off for most of the
resistor’s range. The point
on the PNP that the lamp is
connected to (point E4 on
the base grid) is called the
collector, hence the name
for this project.

-15-
Project #130
NPN Collector
OBJECTIVE: To compare
Project #131
NPN Emitter
Compare this circuit to that in
Project 128, it is the NPN
transistor version and works the
same way. Which circuit makes
the lamp brighter? (They are
about the same because both
transistors are made from the
same materials).
OBJECTIVE: To compare
Compare this circuit to that in
Project 129. It is the NPN
transistor version and works the
same way. The same principles
apply here as in Projects 128-
130, so you should expect it to
be less bright than 130 but as
bright as 129.
Project #132
NPN Collector - Motor
OBJECTIVE: To compare
Project #133
NPN Emitter - Motor
This is the same circuit as in
Project 130, except that it has
the motor (M1) instead of the
lamp. Place the motor with the
positive (+) side touching the
NPN and put the fan on it.
OBJECTIVE: To compare
This is the same circuit as in
Project 131, except that it has
the motor (M1) instead of the
lamp. Place the motor with the
positive (+) side down and put
the fan on it. Compare the fan
speed to that in Project 132.
Just as the lamp was dimmer in
the emitter configuration, the
motor is not as fast now.

-16-
Project #134
OBJECTIVE: To make a circuit
Buzzing in
the Dark
Project #136
High Frequency
Touch Buzzer
OBJECTIVE: To build a high
Replace the speaker (SP) with the 6V Lamp
(L2). Now touching your fingers between B1
and D1 creates a quieter but more pleasant
buzzing sound.
Project #137
High Frequency
Water Buzzer
OBJECTIVE: To build a high
Now connect two (2) jumpers to points B1 and
D1 (that you were touching with your fingers)
and place the loose ends into a cup of water.
The sound will not be much different now,
because your body is mostly water and so the
circuit resistance has not changed much.
Project #138
Mosquito
OBJECTIVE: To make a buzz like a
Place the photosensitive resistor (RP) into the
circuit in Project 137 across where you were
connecting the jumpers (points B1 and D1 on
the grid, and as shown in Project 134). Now
the buzz sounds like a mosquito.
Project #135
Touch Buzzer
OBJECTIVE: To build a human
Remove the photosensitive resistor (RP) from
the circuit in Project 134 and instead touch
your fingers across where it used to be
(points B1 and D1 on the grid) to hear a cute
buzzing sound.
The circuit works because of the resistance in
your body. If you put back the photosensitive
resistor and partially cover it, you should be
able to make the same resistance your body
did, and get the same sound.
This circuit makes a high-frequency
screaming sound when light shines on
the photosensitive resistor, and makes a
buzzing sound when you shield the
photosensitive resistor.

-17-
Project #139
Project #141
Very Loud
Doorbell
OBJECTIVE: To build a
very loud highly sensitive
Replace the antenna coil (A1)
with the speaker (SP), the sound
is much louder now.
OBJECTIVE: To build a
Project #143
Darkness
Announcer
OBJECTIVE: To play OBJECTIVE: To detect
when someone spins the
Project #142
Doorbell
with Button
Replace the microphone (X1)
with the press switch (S2) and
wait until the music stops. Now
you have to press the slide switch
(S1) to activate the music, just
like the doorbell on your house.
Replace the press switch (S2)
with the photosensitive resistor
(RP) and wait until the sound
stops. If you cover the
photosensitive resistor now the
music will play once, signaling
that it has gotten dark. If the
speaker (SP) is too loud then you
may replace it with the antenna
coil (A1).
Replace the photosensitive
resistor (RP) with the motor (M1),
oriented in either direction. Now
spinning the motor will re-activate
the music.
Project #144
Musical
Motion Detector
OBJECTIVE: To build a
loud highly sensitive voice-
Replace the 6V lamp (L2) with
the antenna coil (A1), the sound
is louder now.
Project #140
Louder
Doorbell
OBJECTIVE: To build a
highly sensitive voice-
Build the circuit and wait until the
sound stops. Clap or talk loud a
few feet away and the music
plays again. The microphone
(X1) is used here because it is
very sensitive.
High
Sensitivity
Voice Doorbell

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Project #145 Radio Music
Alarm
OBJECTIVE: To build a radio music
Project #147
Night Music
Radio
OBJECTIVE: To build a
dark-controlled radio
Put the 100kΩresistor back in as
before and instead connect the
photosensitive resistor between
X and Y (you also need a 1-snap
and a 2-snap wire to do this).
Now your radio plays music when
it is dark.
OBJECTIVE: To build a
dark-controlled radio
Project #149
Radio Gun
Alarm
OBJECTIVE: To build a OBJECTIVE: To build a
light-controlled radio
Project #148
Night Gun
Radio
Replace the music IC (U1) with
the alarm IC (U2). Now your
radio plays the sound of a
machine gun when it is dark.
Remove the photosensitive
resistor. Now connect a jumper
wire between X and Y on the
drawing.
If you remove the jumper now,
the machine gun sound will play
on the radio indicating your alarm
wire has been triggered.
Remove the jumper wire.
Replace the 100kΩresistor (R5)
with the photosensitive resistor
(RP). Now your AM radio will
play the machine gun sound as
long as there is light in the room.
Project #150
Daylight Gun
Radio
OBJECTIVE: To build a
light-controlled radio
Project #146
Daylight
Music Radio
Remove the jumper wire.
Replace the 100kΩresistor (R5)
with the photosensitive resistor
(RP). Now your AM radio will
play music as long as there is
light in the room.
You need an AM radio for this project. Build the
circuit on the left and turn on the switch. Place
it next to your AM radio and tune the radio
frequency to where no other station is
transmitting. Then, tune the adjustable
capacitor (CV) until your music sounds best on
the radio. Now connect a jumper wire between
X and Y on the drawing, the music stops.
If you remove the jumper now, the music will
play indicating your alarm wire has been
triggered. You could use a longer wire and wrap
it around a bike, and use it as a burglar alarm!

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Project #151 Blow Off a Space War
Project #152
Series Lamps
Turn on the slide
switch (S1) and both
lamps will light. If one
of the bulbs is broken
then neither will be on,
because the lamps are
in series. An example
of this is the strings of
small Christmas lights;
if one bulb is damaged
then the entire string
does not work.
Project #153
Parallel Lamps
Build the circuit and turn it on,
you hear a space war. Since it is
loud and annoying, try to shut it
off by blowing into the
microphone (X1). Blowing hard
into the microphone stops the
sound, and then it starts again.
Turn on the slide
switch (S1) and both
lamps will light . If one
of the bulbs is broken
then the other will still
be on, because the
lamps are in parallel.
An example of this is
most of the lights in
your house;if a bulb is
broken on one lamp
then the other lamps
are not affected.