This circuit serves as the basis for a huge set of circuits ranging from led chasers, Knight Rider, Electronic Roulette, Semaphores, etc.
Let’s present here two of this kind of circuits.

The 555 IC is well known for being one of the first Integrated Chips to be invented. Invented in 1971 by the company Signetics has even been used to this day.
This Integrated Circuit has three known operating modes: Mono-Stable, A-Stable and Bi-stable. In the circuit we are going to build, it will work in A-Stable mode.


In this mode the circuit places a set of pulses with a certain frequency on its output pin. The Frequency is determined by the resistor and capacitor values used in the circuit.

The 4017 IC is also known as “Decade Counter” places a pin up in a sequence as it is given clock pulses.

In this circuit there is a variable resistance that allows adjusting the frequency.



Bill of materials (BOM)

  • For the base circuit:

  • 1x NE555

  • 1x CD4017
  • 1x 50K Ohms Variable Resistor
  • 1x 10k Ohms Resistor
  • 1x 2.2k Ohms Resistor
  • 1x 1uF Capacitor (Ceramic or Electrolytic)
  • 1x 3.3 to 9 V Battery

  • Optionally for frequency monitoring

  • 1x 470 Ohm Resistor

  • 1x 3mm LED

  • For the Led Chaser circuit:

  • 10x 5mm LEDs
  • 1x 470 Ohm Resistor


  • For the Knight Rider circuit:
  • 6x 5mm LEDs
  • 1x 470 Ohm Resistor
  • 8x 1N4148 Diodes


IC Pin-out


Links from where the circuits were based:

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