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The Timer NE555

Put the NE555 with the deepening on the left side in front of you. The illustration shows you the pins and their functions. You recognize how the NE555 is supplied with power: On PIN 1 (0V) and PIN 8 (In these experiments +9V).

A timer NE555. (Enlarge)

Pin assignment NE555

On the NE555 a timer circuit is preprogrammed, consisting mainly of two comparators and a RS-latch. This is shown in the internal circuit diagram...

Internal circuit diagram timer NE555

Circuit symbol timer NE555.

A brief description of the pins...

Pin Symbol Name Description Experiments
1 GND GROUND Ground (0 V) Exp. 1
2 TRIG TRIGGER Sets the timer. Exp. 4
3 OUT OUTPUT Output of the timers Exp. 3
4 RESET RESET Forced reset of the timer. Exp. 6
5 CTRL CONTROL Reference voltage Exp. 2
6 THR THRESHOLD Resets the timer. Exp. 5
7 DIS DISCHARGE Open-Kollektor outout Exp. 7,8,9
8 Vcc Supply voltage ( 3 - 15 V ) Exp. 1

Description of the various inputs and outputs of the NE555.

In the following experiments the functioning of the individual inputs and outputs become clearly...