Digital electronics, Electronics components, Hobby, Integrated circuits, Projects

2 digital electronics projects

In this post are shown 2 digital electronics projects, using DIP integrated circuits: luminous effect with 74HC595 and a semaphore.

Project with 74HC595

This project creates light effect using the shift register 74HC595. This chip has already been shown in the post whose link is below.

Shift registerClick here

Material list:

  • Printed circuit board (PCB).
  • 1 integrated circuit 555.
  • 1 electrolytic capacitor of 4.7 μF x 100V (the voltage can be from 16 V).
  • Resistors: 8 of 220 Ω, 1 of 470 Ω and 1 of 10 kΩ.
  • LEDs: 2 reds, 2 greens, 2 blues and 2 yellows.
  • 1 push-button switch with 6 pins.
  • 1 74HC595.
  • 2 male connectors pins.
  • 4 AA batteries.
  • 1 support for 4 batteries.
digital electronics schematics 1
The project’s schematics.
digital electronics project 1
The project in printed circuit board.

How does it work?

74HC595 pins
74HC595 pin diagram. Source: Conrad.

Input enable (pin 13) must be linked to the GND or the chip won’t work. The pin 10 is on “HIGH” level, because the master reset function isn’t used. When the latch (pin 12) is on “LOW” level, data that come from pin 14 enter in the shift register. When latch passes to “HIGH” level, the chip can’t receive data and stored data on shift register are transferred to storage register.

74HC595 logic diagram
74HC595 logic diagram, indicating the pins’ numbers. Source: Apogeeweb.

In this project, the latch (pin 12) and the clock pin 11 receive the same square signal from 555 astable. When there is a connection between the connectors, when the button is pressed, LEDs turned on in sequency and pressing it again, LEDs turned off in sequency.


This is a semaphore without microcontroller. Using an astable 555, logic doors and the integrated circuit 4017.

Post about the operation of 4017Click here

Material list:

  • Printed circuit board.
  • Wires.
  • 1 100 kΩ potentiometer.
  • 1 10 μF x 25 V electrolytic capacitor.
  • Resistors: one of 1 kΩ and other of 15 kΩ.
  • 1 CD4017.
  • 1 CD4072.
  • One 74LS02.
  • 8 male connectors for wires.
  • LEDs: 2 reds, 2 yellows and 2 greens. Each one must have a resistor in series with values that can be between 220 and 470 Ω. Or each set of 3 colors can have only 1 resistor.
Were used these LED modules, but they can be replaced with individual LEDs with current limiting resistors.

How does it work?

semaphore schematics
The circuit’s schematics. Click on the image to zoom it.

The 555 astable generates a low frequency signal, it can be adjusted by potentiometer. This signal goes to the 4017, whose outputs are linked to a combinational circuit with 8 inputs that makes the LEDs light up like in a semaphore. If one is green, other must be red and vice-versa.

4072 pinout
The CD4072 have 2 OR logic doors with 4 inputs. Source: Wikimedia.
74LS02 pinout
The 74LS02 has 4 NOR logic gates. Source: Circuits Diy.
Showing how the circuit works.
semaphore in PCB
The circuit in PCB connected to a DC power source.

Demonstration video

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About Pedro Ney Stroski

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