Free Online Circuit Simulator for Digital Logic

What You Can Build

Our circuit simulator supports every fundamental building block of digital electronics. Drag components onto the canvas, wire them up, toggle inputs, and watch the circuit compute in real time. Start simple and build up to complex systems:

• Basic logic gates — AND, OR, NOT, NAND, NOR, XOR, XNOR. The foundational primitives of all digital logic.
• Combinational circuits — multiplexers, decoders, encoders, half adders, full adders, ripple-carry adders, and comparators.
• Sequential circuits — SR latches, D flip-flops, JK flip-flops, T flip-flops, registers, and counters with clock input.
• Display components — LEDs, seven-segment displays (with BCD decoder), and hex displays for visualizing output.
• Custom ICs — build a subcircuit once, save it as a reusable component, and drop it into larger designs. Great for hiding complexity in large projects.
• Input devices — toggle switches, push buttons, clock generators with adjustable frequency, and constant sources.

How It Works

The simulator uses an event-driven propagation model. When you toggle an input, the change ripples through the circuit: each gate recomputes its output, and downstream gates update only if their inputs changed. This approach is both fast and realistic — it mirrors how real digital hardware propagates signals.

For sequential circuits with clocks, the simulator ticks at a configurable frequency. You can pause the clock, step one cycle at a time, or run continuously at speeds from 1 Hz to 1 kHz — slow enough to observe flip-flop transitions, fast enough to test counters and state machines.

Why Choose Our Circuit Simulator

Use Cases

• Computer science students — complete digital logic homework, verify Karnaugh map simplifications, and practice before exams.
• Electrical engineering courses — lab assignments for digital electronics, CPU architecture, and embedded systems classes.
• Self-learners — working through resources like Nand2Tetris, Code by Charles Petzold, or Ben Eater's 8-bit breadboard computer series.
• Teachers — create interactive demonstrations during lectures, record circuit behavior for asynchronous students.
• Hobbyists — prototype circuits before breadboarding with real 74-series chips or FPGAs.

Project Ideas to Try

New to digital circuits? Here are projects that progressively build your intuition:

1. Half adder (2 gates) — adds two 1-bit numbers, outputs sum and carry. The simplest arithmetic circuit.
2. Full adder (5 gates) — adds three 1-bit inputs (A, B, carry-in). Building block for multi-bit adders.
3. 4-bit ripple-carry adder (4 full adders) — adds two 4-bit binary numbers. Classic first-semester project.
4. 4-bit magnitude comparator — outputs whether A > B, A = B, or A < B.
5. SR latch and D flip-flop — your first taste of memory and feedback.
6. 4-bit binary counter — chains D flip-flops to count clock pulses 0-15.
7. Seven-segment decoder — converts 4-bit BCD to seven-segment display signals. Test your Karnaugh map skills.
8. Traffic light controller — a finite state machine with three lights and timing. Great intro to sequential logic.

Frequently Asked Questions

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