555 learning kit

555 Timer Learning Kit

Electronics and PCB Design — Project 1 Designed for the Electronics Engineering department of Pragyan College

Author: Shambo Ghosh

Overview

The 555 Timer Learning Kit is a compact, self-contained teaching board built around the classic NE555 timer IC. It lets first-year students turn a knob, swap a timing capacitor, and watch the resulting waveform live on an OLED screen — connecting the maths of RC timing to something they can actually see.

The board's 555 runs in astable mode, generating a slow square wave. An ATmega328P microcontroller samples the 555's output (and the capacitor's charge/discharge ramp) through its ADC, buffers the samples, and plots them to a small SSD1306 OLED display — mapping voltage to vertical pixels and time to horizontal pixels.

Features

• Astable 555 oscillator core (NE555P)
• Adjustable timing via two potentiometers (RV1, RV2) for real-time frequency/duty-cycle changes
• ATmega328P-P microcontroller sampling the waveform via onboard ADC
• I²C SSD1306 OLED for live waveform visualisation
• Power-state and output-state status LEDs (D2, D3)
• Reverse-polarity protected DC barrel jack power input (1N4007 protection diode)
• Onboard decoupling and filtering across the 555, MCU, and OLED rails
• Dedicated test points (TP1, TP2 / TP_OUT, TP_CAP) for bench-oscilloscope probing
• Onboard AVR ISP programming header (J2)

Signal Flow

555 Astable Core → Signal Conditioning → ATmega328P (ADC + buffering) → SSD1306 OLED
                                     ↘ Test Points (bench scope)

Hardware Summary

Full part numbers and quantities are listed in the BOM included with this repository.

Repository Structure

555-timer-learning-kit/
├── Schematic/           # KiCad schematic (555_learning_kit.kicad_sch)
├── PCB/                 # KiCad PCB layout files
├── Gerbars/             # Manufacturing Gerbers + drill files
├── Firmware/             # MCU firmware (sampling, buffering, OLED plotting)
├── docs/                # Design report, BOM, datasheets, 3D renders
└── README.md

Note: the local 555_learning_kit-backups/ folder (KiCad's auto-save backups) is left out of the repo — see the .gitignore note below.

Getting Started

1. Clone the repository.
2. Open the schematic and PCB files with KiCad 9.0.7 (or later).
3. Review the BOM in docs/ for orderable part numbers before fabrication.
4. Send the Gerbers in gerbers/ to your preferred PCB fabricator.
5. Flash the firmware in firmware/ to the ATmega328P via the ISP header (J2).

Design Notes

• The astable stage is intentionally tuned to run slowly (a few Hz to a few hundred Hz) so the waveform is easy for both the ADC and the OLED to capture and redraw smoothly.
• Signal conditioning sits between the 555 output/capacitor node and the ADC inputs to keep both within safe input range.
• I²C pull-ups are included on the SDA/SCL lines to the OLED.

License

MIT — feel free to adapt this kit for your own teaching or learning purposes.

Acknowledgements

Designed as part of the Electronics and PCB Design Project-1 assignment for Pragyan College's first-year learning module.