scratchboard.io

Scratchboard is a web-based electronics lab that lets you design and simulate circuits directly in your browser. You can build three types of projects: Arduino sketches with full microcontroller emulation, digital logic circuits with gates and flip-flops, and analog DC circuits with components like resistors and LEDs. Everything runs online with no downloads or physical hardware required—you just open the website and start building.

The tool stands out with its specific, powerful features. It includes a full AVR emulator that runs Arduino code with support for GPIO, PWM, timers, and interrupts. You get real-time simulation for both digital signal propagation and analog circuit analysis, showing node voltages and currents. The editor also emulates hardware displays like LCDs and OLEDs, rendering them pixel-perfectly as your code runs. An integrated code editor with C++ syntax highlighting sits right beside your circuit diagram.

Scratchboard is ideal for electronics students learning circuit design, makers prototyping Arduino projects before buying parts, and educators teaching hardware concepts without a physical lab. You can use it to test a new sensor configuration, debug a logic gate circuit, or demonstrate how a voltage divider works—all without any setup time or cost for components.