Page 51 - Electronics Starter Kit_EN

Wiring diagram

12.4 Circuit Explanation

In this circuit we connected the pins 4 and 8 to 5V (it is okay if we did not connect pin 4), we
connected pin 5 to a 100nF capacitor to remove the noise through it to GND if exists (it is okay if
we remove it), pin 1 to GND, pin 3 to a 1 MΩ resistor then to the base of the transistor, to
understand how this circuit works,let us suppose that C1 is empty, so the voltage on pin 2 is
almost zero, so the output is high, pin 7 will be almost 5V on it so C1 will start to charge, and the
transistor won’t be directly ON, because the current will prefer to go to C3 (empty capacitor) and
it will start to charge, when the voltage starts to be 0.7V the transistor will be in the Active
region, and the LED will start to light up, the more C3 charges, the more IB on the base of the
transistor we get, so the LED will increase the brightness.

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