Double Turn Signals - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.6 Double turn signals

Circuit 17: Awesome double turn signals
Setup information
Install the two transistors as shown in Fig. 2.17. Install the two light-emitting diodes. Now it is time for the
six resistors. Finally insert the eight jumpers. Check the placement on the board again and only then con-
nect the battery.
Experiment
If everything is wired correctly, the two LEDs will start flashing alternately. The flashing frequency is at 2 Hz.
Try out other values for the electrolytic capacitors C1 and C2 and the resistors R2 to R5. At times one LED
will glow longer than the other, usually the flashing frequency will be different; and at times the circuit will
not work at all. Then no LED will go on, or one will be steady lit or the other will not turn on at all.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.17.
42
Components required:
2 x 2N3904 transistor,
1 x red LED, 1 x green LED,
2 x 1 kΩ resistors,
2 x 22 kΩ resistors,
2 x 100 kΩ resistors,
2 x 10 μF electrolytic capac-
itors, 1 x breadboard, 1 x 9V
battery with clip connector
Fig. 2.17: Awesome double turn
signals