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 Component Pins Description W65C02S 40-pin DIP 8-bit microprocessor with 16-bit address bus 28C256 28-pin DIP 32KB parallel EEPROM W65C22 40-pin DIP Versatile Interface Adapter (VIA) 62256 28-pin DIP 32KB static RAM Logic & Timer ICs Component Pins Description NE555 8-pin DIP Timer IC for timing and oscillation 7400 14-pin DIP Quad 2-input NAND gate 7402 14-pin DIP Quad 2-input NOR gate 7404 14-pin DIP Hex inverter (NOT gate) 7408 14-pin DIP Quad 2-input AND gate 7432 14-pin DIP Quad 2-input OR gate Passive & Active Components Component Description LED Light emitting diode (various colors) Resistor Current limiting (configurable values) Capacitor Filtering and timing (ceramic/electrolytic) Crystal Clock oscillator Switch Toggle switch (latching) Button Momentary push button Potentiometer Variable resistor Photoresistor Light-dependent resistor 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 Define breadboard dimensions and grid Place power rail connections (+5V and GND) Add LED component with anode/cathode orientation Place current-limiting resistor Draw wire connections between components Add labels and annotations Creating a 555 Timer Circuit Place NE555 IC on breadboard (pins 1-4 left, 5-8 right) Connect pin 1 (GND) to ground rail Connect pin 8 (Vcc) to power rail Add timing resistors and capacitors Wire trigger and threshold connections Connect output to LED or other load Creating a 6502 Microprocessor Layout Place W65C02S centered on breadboard Add 28C256 EEPROM for program storage Place W65C22 VIA for I/O Add 7400-series logic for address decoding Wire address bus (A0-A15) Wire data bus (D0-D7) Connect control signals (R/W, PHI2, RESB) Add reset button and clock crystal Component Pinout Quick Reference 555 Timer (8-pin DIP) Pin Name Function 1 GND Ground (0V) 2 TRIG Trigger (< 1/3 Vcc starts timing) 3 OUT Output (source/sink 200mA) 4 RESET Active-low reset 5 CTRL Control voltage (bypass with 10nF) 6 THR Threshold (> 2/3 Vcc resets) 7 DIS Discharge (open collector) 8 Vcc Supply (+4.5V to +16V) W65C02S (40-pin DIP) - Key Pins Pin Name Function 8 VDD Power supply 21 VSS Ground 37 PHI2 System clock input 40 RESB Active-low reset 34 RWB Read/Write signal 9-25 A0-A15 Address bus 26-33 D0-D7 Data bus 28C256 EEPROM (28-pin DIP) - Key Pins Pin Name Function 14 GND Ground 28 VCC Power supply 20 CE Chip enable (active-low) 22 OE Output enable (active-low) 27 WE Write enable (active-low) 1-10, 21-26 A0-A14 Address inputs 11-19 I/O0-I/O7 Data bus 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 Color Purpose Red +5V / Power Black Ground Yellow Clock / Timing Blue Address bus Green Data bus Orange Control signals White General purpose LED Colors Color Forward Voltage Red 1.8V - 2.2V Green 2.0V - 2.2V Yellow 2.0V - 2.2V Blue 3.0V - 3.5V White 3.0V - 3.5V Build Examples Build 1 — Single LED
Components: Red LED, 220Ω resistor, jumper wires, power source
Steps:
Insert black jumper wire from power GND to row A5 Insert red jumper wire from power +5V to row J5 Place LED with cathode (short leg) in row aligned with GND Place 220Ω resistor between power and LED anode Build 2 — 555 Astable Blinker
Components: NE555, LED, resistors (10kΩ, 100kΩ), capacitor (10µF)
Steps:
Place 555 IC straddling center channel Connect pin 1 to GND, pin 8 to +5V Connect pin 4 to pin 8 (disable reset) Wire 10kΩ between pin 7 and +5V Wire 100kΩ between pins 6 and 7 Wire 10µF between pin 6 and GND Connect pin 3 (output) to LED circuit Troubleshooting Issue Solution LED doesn't light Check polarity (anode to +, cathode to -) Circuit doesn't power Verify power rail connections IC not working Check VCC and GND pin connections 555 not oscillating Verify threshold/trigger capacitor wiring Microprocessor stuck Check RESB is HIGH after reset pulse 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