Quiztimer - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

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.
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.
Components required:
2 x 2N3904 transistors,
1 x red LED, 1 x 10 kΩ
resistor, 2 x 1 kΩ resistors,
1 x 100 kΩ resistor,
1 x 10 μF electrolytic
capacitor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.78: Quiztimer 3 seconds
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