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The 555 Timer in Astable Mode to generate clock frequencies.

Setting up this breadboard I used +/- buses on both sides of the board to eliminate as many cross over wires as I could. What you can't see in the picture is a small wire connecting the middle pin to the bottom pin on the 100K trimmer, take a look at the circuit diagram below the picture. The other thing you can't see well is that the anode (short wire) on the 0.22 microfarad capcitor and one leg of the 0.01 ceramic microfarad capacitor are hooked to the same bus and grounded by the green wire on the right of the picture.

Parts List:

  1. Breadboard
  2. NE555P IC
  3. 100 kilo-ohm trimmer potentiometer
  4. Capacitors (one each): 0.01, 0.22, 100 microfarads
  5. Resistors: Two 10 kilo-ohm, One 47 ohm
  6. Hookup wires
  7. Suggested: One 8 ohm 2 inch speaker

Breadboarding the 555.

Ok, how do I know it works? You could hook it up to an oscilloscope but there is a much cheaper way. Hook up a small 8 ohm speaker, one lead to either negative bus, the other to the anode side of the 100 kilo-ohm capacitor. Be sure you have connected the two positive busses together and the two negative busses together, then apply +5V. You can adjust the sound with the trimmer.

555 Pinout and Circuit.

Remember the wave form I talked about in the 555 One Shot example? It generated one pulse each time I pushed the button. Look at the wave form for the 555 Astable. The Timer is triggering itself here, generating a regular clocked pulse the frequency of which you can adjust with the trimmer.