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Project Notes

#551 SN76477 Prop Plane

Testing the SN76477 propeller plane sound effect configuration


Here’s a quick demo..



The Texas Instruments SN76477 is a complex sound generator chip from the late 1970’s and still reasonably easy to find as refurb or new-old stock. It was covered in some detail in Elektor Magazine 1981-03, p3-22 - “Multiple Sound Effects Generator”.

It was apparently widely used in arcade games and synthesizers and does its magic by integrating a number of subsystems:

  • low frequency oscillator
  • noice generator
  • voltage controlled oscillator
  • envelope generator and modulator
  • mixer
  • output preamp

Features are variously enabled/controlled via pins with either:

  • resistor
  • capacitor
  • logic level
  • analog voltage level

The data sheet describes the configuration for a number of specific sound effects, including:

  • steam train/propeller plan
  • race car motor/crash
  • siren/space war/phasor gun
  • gunshot/explosion
  • bird chirp
  • musical organ
  • steam train with whistle

As a first simple demonstration, I’ve put the “propellor plane” on a breadboard below.

Breadboard Adapter

The SN76477 comes in unusual “N” and “NF” DIP sizes. I think these correspond to JEDEC MS-011 and JEDEC MS-010.

The pin and row spacing is not compatible with a breadboard so I whipped up a simple adapter with some protoboard. I didn’t go full dead bug, as I wanted to keep the pin assignments in conventional arrangement.



This is the “propeller plane” configuration described in the data sheet.

The “speed” of the engine is controlled with a variable resistor input to the low frequency oscillator on pin 20.




Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

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.