User manual

18 Light organ
Open the door number 18, and take out a 330 k
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resistor (orange, orange, yellow). Besides, integrate the LED as a light sensor again. Now you can change the tone
by a torch or any other light source. The closer the lamp the higher the frequency. The expression "light organ" mostly stands for a device, where the sound is
controlled by the light. Here, it is vice versa: Light defines the tone pitch.
Info: The circuit uses again a buffer amplifier for an
uninterrupted tone generation. With the LED as a photo-
diode, only small charging current occurs at medium
brightness. However, adjusted resistors make the tone
sufficient and shift it to a well playable range.
Mission: Play a Christmas carol with a bright torch. If the
carol is recognisable, you get: 5 points.
19 Light telegram
You will find a 10 k
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resistor (brown, black, orange) behind the door number 19. Make a tone generator, which can be switched on by a light source. The yellow
LED acts as a light sensor, the red LED - as an electronic switch of the tone generator. The circuit is a recipient of light telegraphy. Send e.g., an SOS emergency call
(… --- …), which can be understood by everyone.
Info: components of the circuit are already known. The
output of the left op-imp is positive in idle state. The red
LED now conducts and thus stops the tone generator. If the
sensor current is sufficiently high, the output of the light
sensor is toggled. The red LED is then operated in the
reverse-biased direction and the tone generator are
switched on.
Mission: integrate a switch contact or a touch sensor as a
Morse key in parallel to the sensor LED. The light recipient,
thus becomes a transceiver. You can answer the received
messages: 4 points.
20 Siren
Open the door number 20, and take out a 33 k
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resistor (orange, orange, orange). Make a siren. All four amplifiers of the LM324 together are used here for the first
time. Due to many components used, design becomes really complicated.
Info: the circuit includes two oscillators of different frequency. A voltage slowly rising and falling, which actually
reaches the tone generator through the buffer amplifier and modulates input voltage there, is directly applied to
the electrolytic capacitor of the first oscillator. The highest tone pitch is achieved at the medium voltage. The