Page 39 - Electronics Starter Kit_EN

You can take a look on the block diagram, and it is okay if you do not understand it well.

Let us take a look at the pins of NE555:
1- Ground: We connect it to the GND.
2- Trigger: When the voltage falls at this pin, the Output pin (3) goes high and a timing interval
starts.
3- Output: We call this output Push-Pull, because when it is high, it will give 5V, when it is low, it
will give GND.
4- Reset: Timing interval will Reset if we connect this pin to GND, and it will not start again until
the voltage on this goes to 0.7V or higher.
5- Control: It is connected to the internal voltage divider (three 5kΩ resistors), but in this lesson
we will not use this pin, so we connect it to the GND using a small value capacitor, so we ensure
if there is any noise will go directly to GND.
6- Threshold: If the voltage on this pin is higher than Control pin (5), the timing interval ends.
7- Discharge: We use this pin to discharge the capacitor.
8- VCC: We connect it to 5V.

Below you can see the numbering of NE555 timer pins.

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