Circuit Builder
Drag components onto the grid. Connect their terminals with wires, change their settings and see how the circuit responds.
Components
Drag onto the grid, or tap a part then tap a grid point.
Circuit grid
Green circles are connection points. Wires meet at grid dots; crossing wires join. Zoom in or use Pan grid for precise wiring.
About Circuit Builder
Build circuits using cells, switches, lamps, resistors, meters and other components. Explore voltage and current, adjust component values and compare independent circuit canvases.
Add canvases above the grid and switch between them. Export the current full grid as PNG, or download every canvas as a separate Word page or PowerPoint slide. Circuit files and images are processed locally in your browser.
Related tools
How to build and read a circuit
Drag or tap components onto the large grid. Start a wire at a green terminal, drag through grid dots, then release at another terminal. Use the wire tool to start from an existing wire. Press R or Rotate to turn a part by 90°; four turns make a full rotation.
Set cell voltage, resistance, capacitance or an AC supply’s RMS voltage and frequency in the settings panel. Each numeric value has a box and slider. Ambient sliders control all thermistors and light dependent resistors. Switches work directly on the board.
Readings beside the symbols give total RMS voltage, except for ammeters, which show current. Use Show labels to identify components by name. The settings panel also shows current and other results. Lamps, LEDs, motors and buzzers respond to calculated power or current. Meters have high or low resistance so they affect the circuit realistically.
555 astable module: Its GND and OUT terminals model a prewired 555 circuit. The internal timing parts give a high time of about 0.693(R₁ + R₂)C and a low time of about 0.693R₂C, with resistance in ohms and capacitance in farads. The physical eight-pin chip also has supply, trigger, reset and other connections.
Canvases: Add a new canvas using + New canvas above the grid. Each tab keeps its circuit, conditions, view and undo history. Double-click a tab to rename it. All canvases are saved in this browser. Word and PowerPoint exports include every tab in order, one full-grid image per landscape page or slide. Export: Download full-grid PNG includes the whole grid and all placed circuits, regardless of zoom or scroll position. Use the Values checkbox above the grid to show or hide readings. Word and PowerPoint exports use the current checkbox setting for every canvas; the settings panel still shows measurements.
Ideal mode: Tick Ideal for GCSE calculations with ideal voltage sources, non-loading voltmeters and negligible voltage drops across closed switches, ammeters and intact fuses. Untick it for the original realistic model. The Text slider adjusts reading sizes on the grid and in exports. Model limits: This is a learning model using ideal wires and simplified fixed resistance for lamps, motors and buzzers. Sources have a small internal resistance. AC readings use steady-state sinusoidal analysis; capacitors and inductors include frequency dependence. Diodes and LEDs are approximated for DC and do not rectify AC. Real components can heat, fail or behave differently. Follow your teacher’s instructions for physical circuits.