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THE 555 TIMER V. Ryan © 2002-2004 |
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This integrated circuit is used for timing. Many circuits are composed of timers and the most common of them all is the 555 Integrated Circuit. The 555 integrated circuit (IC) is a chip that is used in many school projects and commercially made items such as video recorders and timers. You must understand the basic workings of this important IC. |
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The 555 has eight pins (legs) but the function of two are
very important. These are pin two and three. PIN 2. This pin is where the current / voltage enters the chip and starts the timing sequence or starts to count. PIN 3. This is where the current comes out after the timer has completed counting. |
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A SIMPLE 555 CIRCUIT |
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The circuit below is a simplified version of a 555
circuit. It is a timer. When the switch is pressed a current / voltage goes
into the IC through pin two (the input pin). The chip starts counting and
when it has finished counting it ‘pulses’ a current or voltage from pin
three (the output pin). This voltage from pin three switches a transistor
and allows the LED to light. |
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