Data Sheet

You will need:
You will need:
64
Light-controlled
flasher
In addition to the fixed-value resistors, you also have
the phototransistor. With its help, you can use changes
in external lighting conditions to adjust the flash tempo.
• Batterybox • 100-μFcapacitor
• 17X-connectors • 0.1-μFcapacitor
• 6I-connectors • RedLED
• 2L-connector • GreenLED
• 2Transistors • Selectorswitch
• Phototransistor • Bluewire
• alltheresistors • Redwire
Here’s how:
1. Insert the phototransistor into the blinker circuit
from Experiment 61 in place of the resistor mounted
on the left.
2. Shade the phototransistor or expose it to bright
light and observe how the blink
frequency changes.
3. Also try inserting different resis-
tors on the right, and compare the
results.
4. Swap the capacitors and check
what happens.
How it works:
The darker the phototransistor, the higher
its resistance value. That causes the blink
frequency to drop as it gets less light.
63
Adjustable sound
pitch
It can be a little bit tedious to reinsert resistors. You
can use the selector switch to choose between two
tone pitches.
• Batterybox • 100-μFcapacitor
• 20X-connectors • 0.1-μFcapacitor
• 7I-connectors • Speaker
• 3L-connector • GreenLED
• 2Transistors • Selectorswitch
• 120kΩResistor • Bluewire
• 22kΩResistor • Redwire
• 8.2kΩResistor
Here’s how:
1. After assembly, you will hear a tone in the speaker.
2. Push the selector switch to the other setting: The
sound changes.
How it works:
When you slide the selector switch, it connects the
22-kΩ resistor in series with the 8.2-kΩ resistor,
which changes the left capacitor-resistor
combination and, thus, the sound as
well.
light and observe how the blink
frequency changes.
Also try inserting different resis
tors on the right, and compare the
results.
4.
what happens.
How it works:
The darker the phototransistor, the higher
its resistance value. That causes the blink
frequency to drop as it gets less light.
Shade the phototransistor or expose it to bright
light and observe how the blink
sound changes.
How it works:
When you slide the selector switch, it connects the
light and observe how the blink
frequency changes.
3.
Also try inserting different resis
tors on the right, and compare the
results.
4.
what happens.
How it works:
The darker the phototransistor, the higher
its resistance value. That causes the blink
frequency to drop as it gets less light.
When you slide the selector switch, it connects the
22-kΩ resistor in series with the 8.2-kΩ resistor,
which changes the left capacitor-resistor
combination and, thus, the sound as
When you slide the selector switch, it connects the
When you slide the selector switch, it connects the
22-kΩ resistor in series with the 8.2-kΩ resistor,
which changes the left capacitor-resistor
When you slide the selector switch, it connects the
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Electronics Learning Circuits Manual.indd 57 3/29/11 2:28 PM