Oscilloscope Spirograph

A mixed-signal oscilloscope spirograph generator designed in JLC EDA Pro.

This project is an improved and integrated open-source version based on the final coursework project for Tsinghua University's Basic Experiments for Electronic Circuits and Systems course.

The board generates two related analog signals for drawing spirograph-style parametric patterns on an oscilloscope in X-Y mode. It is a hardware-first visual electronics project: digital logic creates stable frequency relationships, analog stages shape the waveforms, and the oscilloscope turns the result into moving geometry.

Features

• Single-board mixed-signal signal generator.
• Schmitt-trigger oscillator and digital divider section.
• Active low-pass filtering for smoother waveform components.
• Multi-stage phase-shift networks.
• Summing and amplitude-control stages for shaping the final X/Y signals.
• USB-C power input with onboard power-conversion circuitry.
• JLC EDA Pro project export and Altium schematic/PCB export included.

Signal Chain

Oscillator
  -> digital divider
  -> active low-pass filters
  -> phase-shift stages
  -> summing / amplitude controls
  -> oscilloscope X and Y inputs

The project is designed for visual experimentation rather than precision signal synthesis. The most interesting results come from tuning the divider ratio, oscillator frequency, phase shift, and summing amplitude together while watching the oscilloscope display.

Hardware Overview

The design combines digital logic, analog filtering, and power-conversion circuitry.

Device / Block	Role
CD40106BE	Schmitt-trigger oscillator / conditioning
CD4011BE and SN74HC00N	Digital support logic
SN74HC161N	Counter / divider logic
LM348N / LM348N/NOPB	Quad op-amp stages for filtering, phase shifting, buffering, and summing
USB-C input and power-conversion components	Onboard supply generation

Key Considerations

1. Oscilloscope Mode

   Use the board with an oscilloscope in X-Y display mode. Connect the two final analog outputs to the X and Y channels.

2. Frequency Ratio

   The visible pattern depends strongly on the selected divider ratio. Stable integer-related frequencies produce repeatable closed figures.

3. Filtering

   The divider outputs begin as square waves. The active low-pass sections emphasize the fundamental component and reduce harmonic content before the phase and summing stages.

4. Phase Shift

   The all-pass phase-shift stages are an important part of the pattern-generation chain. Small phase changes can noticeably alter the displayed figure.

5. Summing and Amplitude

   The final pattern is shaped by the relative amplitudes of the summed signal paths. Adjust the controls gradually while watching both clipping and trace size on the oscilloscope.

6. Power and Grounding

   Because the board mixes digital switching and analog signal paths, keep the power input stable and avoid unnecessary long ground loops during testing.

Repository Contents

File	Description
Altium_Oscilloscope_Spirograph_2026-05-06.zip	Altium export containing the schematic and PCB files.
ProPrj_Oscilloscope_Spirograph_2026-05-06.epro	JLC EDA Pro project export.
LICENSE	MIT license.
README.md	Project introduction and design notes.

Opening the Project

Use ProPrj_Oscilloscope_Spirograph_2026-05-06.epro to import the project back into JLC EDA Pro.

Use Altium_Oscilloscope_Spirograph_2026-05-06.zip if you want to inspect or modify the exported Altium schematic and PCB files.

Project Status

This repository contains the editable project exports. Manufacturing outputs such as Gerbers, BOM files, placement files, and assembly drawings are not included unless exported separately.

Background

• Background article: https://mp.weixin.qq.com/s/7FQKxnxlLlElwnbqzJV7Ww

License

This project is released under the MIT License.