103
2.31 Quiztimer
Circuit 78:
Quiztimer 3 seconds
Setup information
Install the two transistors, the diode and the four resistors as shown in
Fig. 2.78
. The seven jumper wires
come next. Finally, insert the six jumper wire, 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 k
Ω
resistor, 2 x 1 k
Ω
resistors,
1 x 100 k
Ω
resistor,
1 x 10 μF electrolytic
capacitor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.78:
Quiztimer 3 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 2 seconds. During this time, the answer
must be given or the next move must be performed.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.78.
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...
