Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 117

Circuit 94: Slow LED flash
Setup information
Install the two transistors, the LED, the three resistors and the three electrolytic capacitors as shown in
Fig. 2.94. The ten jumper wires come next. Check the placement on the board again and only then connect
the battery.
Experiment
If everything is wired correctly, the circuit immediately starts generating very short LED flashes at an interval
of about three seconds. The repetition frequency in our circuit is basically defined by C2, C3. Circuitries of
this kind can be used as a stroboscope in many applications.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.94.
Components required:
1 x 2N3904 transistor,
1 x 2N3906 transistor,
1 x red LED, 1 x 100 Ω
resistor, 1 x 100 kΩ
resistor, 1 x 220 kΩ resis-
tor, 1 x 1 μF electrolytic
capacitor, 2 x 10 μF
electrolytic capacitors,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.94: Slow LED flash
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