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5. Clock Generator Circuits


In this experiment we are going to design a circuit that generates an automatic clock signal, which we can use to drive our digital circuits. So far, we have 'clocked' our circuits manually, but an automatic solution would be preferred if we wish to clock many times in a row. Also, one limitation is that we need a clock signal that is slow enough to see what is happening in the circuit - if we were to have a clock signal of 1 MHz, we would not be able to observe the changes in the circuit as they would occur at the rate of 1,000,000 times per second. We will examine the use of the 555 Timer to output a very low frequency rectangular clock pulse of approximately 1Hz, which we can use to drive our TTL circuits.

Note: The full set of videos is presented on the YouTube channel: DerekMolloyDCU

Equipment Required:

  • A 555 Timer IC (NE555P)
  • Capacitors (10nF, 47uF)
  • Resistors (1kΩ, 10kΩ, 4.7kΩ)
  • Light Emitting Diode - Green
  • Breadboard

Derek Molloy,
27 Apr 2010, 03:58