Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 225

Circuit 202: 3 seconds switch-off delay
Setup information
Install the transistor, the diode, the four resistors and the electrolytic capacitor as shown in Fig. 2.202 fol-
lowed by the four jumper wires and the jumper, which serve as switch (shown dashed). For your guidance,
we labelled the "switch" with Start. Check the placement on the board again and only then connect the
battery.
Experiment
Even if everything is wired correctly, nothing will happen at first. But when you activate the Start switch,
that is, when you insert the wire, the red LED will go on after a short delay. When the "switch" is opened
again, the red LED will continue to glow for a certain time. In our case this delay is about 3 seconds.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.202.
Components required:
1 x 2N3904 transistor,
1 x red LED, 2 x 1 kΩ resis-
tors, 2 x 10 kΩ resistors,
1 x 100 μF electrolytic
capacitor, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.202: 3 seconds switch-
off delay
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