User Guide

Complete guide to using CircuitJS1

Getting Started

CircuitJS1 is a browser-based electronic circuit simulator that allows you to design, build, and analyze circuits in real-time. This guide covers everything you need to know to get started.

Interface Overview

Main Areas

  • Circuit Canvas: The main area where you build and view your circuit
  • Component Menu: Right-click to access all available components
  • Properties Panel: Right-click components to edit their properties
  • Scope Display: Built-in oscilloscope for viewing signals
  • Control Buttons: Play/pause, reset, and other simulation controls

Building Circuits

Adding Components

  1. Right-click on empty space to open the component menu
  2. Navigate through categories (Passive, Active, Logic, etc.)
  3. Click on the component you want to add
  4. Position the component by moving your mouse
  5. Click to place the component

Connecting Components

  1. Click on a component terminal (the small dots)
  2. Drag to another component terminal
  3. Release to create the connection
  4. Double-click on wires to add junction dots

Editing Components

  1. Right-click on any component
  2. Select “Edit” from the context menu
  3. Modify parameters in the dialog box
  4. Click “OK” to apply changes

Component Categories

Mathematical & Economics Components

CircuitJS1 includes specialized components for mathematical operations and economic modeling (system dynamics). These are particularly useful for simulation modeling, control systems, and stock-flow analysis.

Arithmetic Operations

Adder - Adds multiple input voltages: Vout = V1 + V2 + V3 + … - Configurable number of inputs (default: 2) - Linear element using VCVS (no iteration needed) - Symbol: + (summation symbol)

Subtracter - Subtracts input voltages: Vout = V1 - V2 - V3 - … - Configurable number of inputs (default: 2) - Linear element using VCVS (no iteration needed) - Symbol: − (minus symbol)

Multiply by Constant - Multiplies input voltage by a fixed gain: Vout = K × Vin - Configurable gain constant - Can show multiplier or percentage - Linear element (VCVS with fixed gain) - Symbol: ×

Multiplier - Multiplies multiple input voltages: Vout = V1 × V2 × V3 × … - Configurable number of inputs (default: 2) - Nonlinear operation requiring iteration - Useful for power calculations and modulation - Symbol: × (multiplication symbol)

Divider - Divides voltages: Vout = V1 / V2 / V3 / … - Includes division-by-zero protection (epsilon = 1e-9) - Implemented as multiplication by reciprocal - Symbol: ÷

Differentiator - Computes rate of change: Vout = dVin/dt - Calculates time derivative of input voltage - Essential for dynamic system modeling - Uses numerical differentiation - Symbol: d/dt

Integrator - Computes integral: Vout = ∫Vin dt - Integrates input voltage over time - Configurable initial value - Essential for accumulation and control systems - Symbol: ∫ (integral symbol)

ODE (Ordinary Differential Equation) - Solves differential equations: dV/dt = expression - Supports complex mathematical expressions - Multiple integration methods (Euler, RK4) - Variables: input voltages, time (t), constants - Ideal for dynamic system modeling - Shows equation on component

Equation - Evaluates algebraic equations: Vout = expression - Supports arithmetic operations (+, -, ×, ÷) - Functions: sin, cos, tan, exp, log, sqrt, abs - Variables: input voltages (v1, v2, …), time (t) - Constants: pi, e - Shows equation on component

Display & Measurement

Percent/Ratio Meter - Display-only element (doesn’t affect circuit) - Computes ratio: V1/V2 - Two display modes: - Ratio mode: Shows raw division result - Percentage mode: Shows ratio × 100 with % symbol - Configurable scaling (Auto, m, 1, K, M) - Division-by-zero protection

Pie Chart - Visual display of proportional values - Multiple input values shown as pie slices - Automatic percentage calculation - Color-coded segments - Labels with values and percentages - Useful for visualizing resource distribution - Display-only element (doesn’t affect circuit)

Key Properties: - First terminal: numerator (V1) - Second terminal: denominator (V2) - Fixed decimal precision option - Ideal for efficiency calculations and feedback monitoring

Data Management

Table Element - Spreadsheet-like component for equation-based calculations - Multiple columns with configurable types (Asset/Liability/Equity/Computed) - Each cell contains equations using labeled node names or variables (a-i) - Output pins provide voltage outputs for each column - Supports time-based functions: sin(t), cos(t), t - Column synchronization with shared stocks - Visual highlighting of shared columns (yellow)

Key Features: - Configurable rows and columns - Initial values row (optional) - Row descriptions/labels - Cell equations with full expression support - Decimal places control - Collapsed mode for compact display - Table title and units

Godley Table Element - Extended table with integration capabilities - Integrates column sums over time - Integration equation: output = lastOutput + timeStep × gain × columnSum - Outputs current proportional to column sums - Ideal for stock-flow modeling - Shows initial values by default

  • Contains the following parts

  • Flows on each row

    • Orchestrates flow elements in system dynamics models
    • Manages flow calculations and updates
    • Coordinates with stock elements
    • Visual representation of flow network
    • Central control for flow-based simulations

  • Stock Column Elements

    • Central controller for stock-flow systems
    • Manages stock accumulation and depletion
    • Integrates flows over time
    • Tracks multiple stock variables
    • Coordinates with flow master and table elements
    • Essential for system dynamics modeling

Current Transactions Matrix - Displays transaction flows between accounts - Matrix visualization of stock changes - Row and column labels for clarity - Real-time updates during simulation - Useful for economic flow analysis - Shows net flows between system components

Simulation Control

Stop Time Element - Automatically pauses simulation at specified time - Visual stop sign indicator (octagon) - Configurable stop time in seconds - No electrical connections (control element only) - Resets when simulation is reset - Useful for automated testing and time-limited simulations

Key Properties: - Stop time (default: 1.0 seconds) - Visual feedback when stopped (highlighted red octagon) - “STOP” text display with time value

Action Time Element - Triggers actions at specific simulation times - Schedules events during simulation - Multiple action points supported - Useful for automated testing and timed events - No electrical connections (control element only) - Can trigger parameter changes or state transitions

Key Properties: - Action time points (configurable) - Action type and parameters - Visual indicator of scheduled actions

Example Applications

Economic Modeling Use Tables and Godly Tables to model stock-flow systems: - Stocks: Bank accounts, inventory levels, population - Flows: Transactions, production rates, birth/death rates - Auxiliaries: Computed values, ratios, indicators

Control Systems Combine mathematical elements for control algorithms: - Adder: Summing junctions for error signals - Multiply by Constant: Gain stages (P, I, D coefficients) - Differentiator: Derivative control action

Signal Processing Build signal processing chains: - Multiplier: Amplitude modulation, mixing - Divider: Automatic gain control - Percent Meter: Distortion measurement

For traditional electronics components (resistors, capacitors, transistors, logic gates, etc.), see the Electronics Components guide.

Measurement and Analysis

Built-in Oscilloscope

The scope displays voltage and current waveforms in real-time:

  1. Right-click on any wire or component terminal
  2. Select “View in Scope” to add the signal
  3. Adjust time base and voltage scale using controls
  4. Remove signals by right-clicking scope traces

Meters and Probes

  • Voltmeter: Measures voltage across components
  • Ammeter: Measures current through branches
  • Probe: Shows voltage values as text labels

Analysis Features

  • DC Operating Point: Steady-state analysis
  • AC Analysis: Frequency response (when available)
  • Transient Analysis: Time-domain simulation

Simulation Controls

Time Controls

  • Play/Pause (Space): Start/stop the simulation
  • Reset (R): Return circuit to initial conditions
  • Speed Control: Adjust simulation speed

Solver Settings

Access advanced settings through the Options menu:

  • Time Step: Simulation accuracy vs. speed
  • Solver Method: Numerical integration method
  • Convergence: Iteration limits for nonlinear circuits

File Operations

Saving Circuits

  • File Menu > Export as : Save circuit to clipboard
  • File Menu > Export As Text - Text representation to clipboard
  • File Menu > Export As Link - Shareable link

Loading Circuits

  • File Menu > Open File: open from local directory
  • File Menu > Import From Dropbox: Load from Dropbox URL
  • File Menu > Import From Text.: paste from clipboard

Sharing Circuits

  • File Menu > Export As Link - Shareable link
  • Export Image: Save circuit diagram as PNG
  • Print: Send to printer or PDF

Tips and Best Practices

Circuit Design

  1. Start Simple: Build and test basic blocks first
  2. Use Ground: Connect reference points to ground
  3. Label Nodes: Add text labels for clarity
  4. Group Related Components: Organize logically

Debugging

  1. Check Connections: Ensure all nodes are properly connected
  2. Verify Values: Double-check component parameters
  3. Use Scope: Monitor key signals during simulation

Performance

  1. Minimize Scope Traces: Only monitor necessary signals
  2. Adjust Time Step: Balance accuracy with speed
  3. Simplify When Possible: Use ideal components for initial analysis

Keyboard Shortcuts

Shortcut Action
Delete Remove selected
Ctrl+A Select all
Ctrl+C/V Copy/Paste

Troubleshooting

Common Issues

Circuit Won’t Simulate - Check for disconnected nodes - Ensure there’s a ground connection - Verify component values are reasonable

Simulation Runs Slowly - Reduce scope traces - Increase time step size - Simplify the circuit

Oscilloscope Shows Nothing - Check signal connections - Adjust voltage/time scales - Verify simulation is running

Components Behave Unexpectedly - Review component parameters - Check for proper connections - Consider real-world limitations

Getting Help

This guide covers the essential features of CircuitJS1. For advanced topics and development information, see the Building Guide and Contributing Guidelines.