105
Circuit 80:
Quiztimer 30 seconds
Setup information
Install the two transistors, the diode and the four resistors as shown in
Fig. 2.80.
The seven jumper wires
come next. Finally, insert the six jumper wires, which will function as a switch (shown dashed). Check the
placement on the board again and only then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x red LED, 1 x 10
Ω
resis-
tor, 2 x 1 k
Ω
resistors,
1 x 220 k
Ω
resistor,
1 x 100 μF electrolytic
capacitor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.80:
Quiztimer 30 seconds
Experiment
This is a classic circuit with switch-off delay. If everything is wired correctly, the “switch” is On, meaning
that one end of the jumper is not connected. Connect the jumper momentarily. The red LED turns on. When
you open the switch, the quiz clock starts running; in our case this is 30 seconds Naturally, difficult ques-
tions or complex games require more time. The answer must be given or the next move must have followed
during the time the red LED is lit.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.80.
Summary of Contents for ELECTRONICS EXPERIMENTS BOX
Page 4: ......
Page 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Page 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Page 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Page 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
