Legacy Circuit Mockups

A skill for creating breadboard circuit mockups and visual diagrams for retro computing and electronics projects. This skill leverages HTML5 Canvas drawing mechanisms to render interactive circuit layouts featuring vintage components like the 6502 microprocessor, 555 timer ICs, EEPROMs, and 7400-series logic gates.

When to Use This Skill

• User asks to "create a breadboard layout" or "mockup a circuit"
• User wants to visualize component placement on a breadboard
• User needs a visual reference for building a 6502 computer
• User asks to "draw a circuit" or "diagram electronics"
• User wants to create educational electronics visuals
• User mentions Ben Eater tutorials or retro computing projects
• User asks to mockup 555 timer circuits or LED projects
• User needs to visualize wire connections between components

Prerequisites

• Understanding of component pinouts from bundled reference files
• Knowledge of breadboard layout conventions (rows, columns, power rails)

Supported Components

Microprocessors & Memory

Logic & Timer ICs

Passive & Active Components

Grid System

// Standard breadboard grid: 20px spacing
const gridSize = 20;
const cellX = Math.floor(x / gridSize) * gridSize;
const cellY = Math.floor(y / gridSize) * gridSize;

Component Rendering Pattern

// All components follow this structure:
{
  type: 'component-type',
  x: gridX,
  y: gridY,
  width: componentWidth,
  height: componentHeight,
  rotation: 0,  // 0, 90, 180, 270
  properties: { /* component-specific data */ }
}

Wire Connections

// Wire connection format:
{
  start: { x: startX, y: startY },
  end: { x: endX, y: endY },
  color: '#ff0000'  // Wire color coding
}

Step-by-Step Workflows

Creating a Basic LED Circuit Mockup

1. Define breadboard dimensions and grid
2. Place power rail connections (+5V and GND)
3. Add LED component with anode/cathode orientation
4. Place current-limiting resistor
5. Draw wire connections between components
6. Add labels and annotations

Creating a 555 Timer Circuit

1. Place NE555 IC on breadboard (pins 1-4 left, 5-8 right)
2. Connect pin 1 (GND) to ground rail
3. Connect pin 8 (Vcc) to power rail
4. Add timing resistors and capacitors
5. Wire trigger and threshold connections
6. Connect output to LED or other load

Creating a 6502 Microprocessor Layout

1. Place W65C02S centered on breadboard
2. Add 28C256 EEPROM for program storage
3. Place W65C22 VIA for I/O
4. Add 7400-series logic for address decoding
5. Wire address bus (A0-A15)
6. Wire data bus (D0-D7)
7. Connect control signals (R/W, PHI2, RESB)
8. Add reset button and clock crystal

Component Pinout Quick Reference

555 Timer (8-pin DIP)

W65C02S (40-pin DIP) - Key Pins

28C256 EEPROM (28-pin DIP) - Key Pins

Formulas Reference

Resistor Calculations

• Ohm's Law: V = I × R
• LED Current: R = (Vcc - Vled) / Iled
• Power: P = V × I = I² × R

555 Timer Formulas

Astable Mode:

• Frequency: f = 1.44 / ((R1 + 2×R2) × C)
• High time: t₁ = 0.693 × (R1 + R2) × C
• Low time: t₂ = 0.693 × R2 × C
• Duty cycle: D = (R1 + R2) / (R1 + 2×R2) × 100%

Monostable Mode:

• Pulse width: T = 1.1 × R × C

Capacitor Calculations

• Capacitive reactance: Xc = 1 / (2πfC)
• Energy stored: E = ½ × C × V²

Color Coding Conventions

Wire Colors

LED Colors

Build Examples

Build 1 — Single LED

Components: Red LED, 220Ω resistor, jumper wires, power source

Steps:

1. Insert black jumper wire from power GND to row A5
2. Insert red jumper wire from power +5V to row J5
3. Place LED with cathode (short leg) in row aligned with GND
4. Place 220Ω resistor between power and LED anode

Build 2 — 555 Astable Blinker

Components: NE555, LED, resistors (10kΩ, 100kΩ), capacitor (10µF)

Steps:

1. Place 555 IC straddling center channel
2. Connect pin 1 to GND, pin 8 to +5V
3. Connect pin 4 to pin 8 (disable reset)
4. Wire 10kΩ between pin 7 and +5V
5. Wire 100kΩ between pins 6 and 7
6. Wire 10µF between pin 6 and GND
7. Connect pin 3 (output) to LED circuit

Troubleshooting

References

Detailed component specifications are available in the bundled reference files:

• 555.md - Complete 555 timer IC specification
• 6502.md - MOS 6502 microprocessor details
• 6522.md - W65C22 VIA interface adapter
• 28256-eeprom.md - AT28C256 EEPROM specification
• 6C62256.md - 62256 SRAM details
• 7400-series.md - TTL logic gate pinouts
• assembly-compiler.md - Assembly compiler specification
• assembly-language.md - Assembly language specification
• basic-electronic-components.md - Resistors, capacitors, switches
• breadboard.md - Breadboard specifications
• common-breadboard-components.md - Comprehensive component reference
• connecting-electronic-components.md - Step-by-step build guides
• emulator-28256-eeprom.md - Emulating 28256-eeprom specification
• emulator-6502.md - Emulating 6502 specification
• emulator-6522.md - Emulating 6522 specification
• emulator-6C62256.md - Emulating 6C62256 specification
• emulator-lcd.md - Emulating a LCD specification
• lcd.md - LCD display interfacing
• minipro.md - EEPROM programmer usage
• t48eeprom-programmer.md - T48 programmer reference