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Project Notes

#072 NOR7402 - 74LS02 Quad 2-input NOR gate test

Use an Arduino to demonstrate a basic 74LS02 Quad 2-input NOR gate circuit, and plot the results with Processing.


The 74LS02 Quad 2-input NOR gate is from the 7400 series of TTL integrated circuits. “Quad 2-input” means it contains four independent gates each with 2 inputs. “74LS” means this is Low-power Schottky sub-family device (reduced power consumption and switching speed compared to 74S)

Each gate implements standard NOR logic:

A B Y (output)
0 0 1
0 1 0
1 0 0
1 1 0

The 74LS02 is a 5V device with logic levels bounded as follows (from the datasheet):

  • HIGH inputs are recommended to be 2.0V minimum
  • LOW inputs are recommended to be 0.8V maximum
  • HIGH output is 2.7V minimum, typically 3.4V
  • LOW output is 0.5V maximum, typically 0.35V

This circuit demonstrates the basic operation. It uses the Arduino to sequence inputs through the truth table on a single NOR gate. The NOR gate output drives an LED and is also measured by the Arduino with an analog input.


Here’s a sample trace taken with LEAP#090 PlotNValues (a simple Processing sketch). The lower two traces are the gate inputs, and the upper trace is the gate output. The HIGH output voltage measures at 3.42V (a tad over typical value according to the datasheet)

processing trace


The Breadboard

The Schematic

The Build

Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.