Pneumatic Circuit Simulator

Welcome to the Pneumatic Circuit Simulator — a free, browser-based pneumatic systems simulator designed for mechanical engineering students, automation technicians, vocational instructors, and maintenance engineers. This tool serves as a powerful FluidSIM pneumatics online alternative, providing interactive ISO 1219 schematic building, real-time compressed air flow animation, and comprehensive learning modes — all without installation, signup, or licensing fees.

The simulator features 52 pneumatic components including FRL units, 5/2 valves, timer valves, logic gates, vacuum generators, and more. It includes 11 pre-built circuit templates and 4 interactive learning modes (Simulate, Explore, Practice, Quiz). Calculate cylinder force, air consumption, and study circuits ranging from basic direct control to multi-cylinder cascade sequencing.

Select components from the collapsible palette on the left. Click a component to place it on the canvas, or drag it directly. Click on port circles to create connections between components. Click the Run Circuit button to start the simulation and watch compressed air flow through your circuit with animated particles.

Load a pre-built circuit (Direct Control, Speed Control, Auto Return, AND/OR Logic, Time Delay, Sequential, Cascade, Vacuum Pick, Pilot Control, or Stroke Limit) to instantly study a working configuration. Or build from scratch using the 52 available ISO 1219 components.

Air Supply (2): Compressed air source and air reservoir tank. The tank is a working receiver: it charges from the line (watch the fill level and pressure label rise — larger volumes fill slower) and, if the compressor is deleted while running, it takes over as an amber-highlighted reserve supply until its stored air runs out. The compressor also has a finite flow capacity — drive two cylinders (or one large bore) at once and the demand exceeds it, so the supply pressure droops and the status warns “Compressor undersized”. This is the CFM-sizing lesson: pressure and flow can't both be unlimited.

Air Treatment / FRL (3): Filter, pressure regulator, and combined FRL unit for clean, regulated air.

Directional Control Valves (23): 2/2 on/off, 3/2 valves (push button, roller lever, idle return, plunger, solenoid), 5/2 valves (single/double solenoid, pilot), 5/3 valves (closed/exhaust centre), and 4/3 closed centre. ISO 5599 port numbering: 1(P), 2(A), 3(R), 4(B), 5(S).

Flow Control (3): One-way flow control (meter-out), throttle valve, quick exhaust valve.

Pressure Control (2): Relief valve, sequence valve. The relief valve clamps the line, it does not merely open a vent: set an 8 bar relief on a 10 bar supply and every gauge downstream reads 8 bar, because the surplus air is dumped to atmosphere. That is the core ISO 4414 over-pressure lesson, and the status bar reports “Relief valve open — line clamped at setting” while it is cracked.

Logic Valves (4): Check valve, pilot-operated check valve, shuttle valve (OR), dual-pressure valve (AND). The pilot check passes air 1 → 2 freely but blocks the return until pilot port 12 can unseat the cone. That is not a simple on/off test: a real unlockable non-return valve works on a pilot area ratio (selectable 3:1, 4:1 or 5:1), so it opens only when p_pilot × ratio ≥ the blocked pressure plus any outlet back-pressure. Shuttle and AND valves use ISO 11727 port numbers — inputs 1 and 1(3), output 2.

Actuators (4): Single-acting cylinder, double-acting cylinder, rodless cylinder, rotary actuator. All three cylinders take a Load (N) setting and are solved with a real force balance: F = η (p₁A₁ − p₂A₂) with a mechanical efficiency η = 0.85 for seal and guide friction, netting the back-pressure on the opposite piston face. The readout shows that same net effective force — not the textbook p × A — plus a Load Ratio %. FESTO/SMC sizing practice keeps that ratio at 50–70 %; above 70 % the figure turns amber, above 100 % the cylinder stalls. The single-acting cylinder’s return spring is progressive and bore-dependent (about 12 % of the 6-bar force at rest rising to 20 % at full stroke), and it only returns if it can also lift the load. Cylinders also need an exhaust path: air on the opposite face must reach atmosphere or the cylinder simply cannot move — feed one through a closed 2/2 and the trapped air holds it, exactly as it would on the bench.

Vacuum (2): Venturi vacuum generator, suction cup. The vacuum depth is generated by the motive supply pressure, not a fixed setting: below ~1.5 bar the ejector makes no vacuum, and it rises to the rated maximum near 5 bar. Raise the supply and the vacuum deepens; the suction cup shows its live holding force (F = p_vac × A_cup) rise with it — the same formula used in Practice mode, so you can verify your hand calculation on the canvas. Below it the cup also prints the SF2 value: vacuum sizing applies a safety factor of 2 for a vertical lift and up to 4 for horizontal handling or porous parts, so never size a cup on the theoretical number.

Timing (2): On-delay and off-delay timer valves, modelled the way real ones are built — a 3/2 valve plus an air reservoir and a one-way throttle. They have four ports: 1 (supply), 2 (output), 3 (exhaust) and 12 (pilot). The pilot only times the switchover; the output is fed from the timer’s own supply, so remember to connect port 1 or the timer will never produce a signal.

Measurement (3): Pressure gauge, flow meter, proximity sensor.

Sensors (2): Limit switch NC and limit switch NO with roller lever actuation, triggered by cylinder piston position.

Utility (2): Silencer, T-connector.

Components are organised into collapsible categories in the palette. Drag or click to place on canvas. Click port circles to connect components with automatically routed orthogonal paths. Drag connection segments to adjust routing.

11 Pre-Built Templates: Direct Control, Speed Control, Auto Return, AND Logic (two-hand safety), OR Logic, Time Delay, Sequential A+B+, Cascade, Vacuum Pick, Pilot Control, and Stroke Limit.

Simulation: Animated blue particles show air flow direction and speed. Click 3/2 push buttons to toggle during simulation. Pressure gauges show live readings. Cylinders animate extension/retraction. The readout panel shows supply pressure, flow rate (NL/min, shown as scfm in imperial — compressed air is never measured in gal/min), air consumption per full cycle, net cylinder force, speed, and load ratio.

Cylinder speed — and the stopwatch test: compressor flow is quoted in normal litres (NL/min — free air at atmospheric pressure), but the air that fills the cylinder is compressed to line pressure, so the volumetric flow at the piston is Q_N ÷ (p_gauge + 1) and the speed is v = Q_actual ÷ A. Example: 200 NL/min at 6 bar into a 50 mm bore gives 200/7 = 28.6 L/min over 1963 mm² ≈ 242 mm/s. The on-screen stroke is driven by that same number rather than by a separate animation rate, so you can time the piston with a stopwatch and get the readout back: a 300 mm stroke at 100 mm/s takes 3 s. Meter-out flow controls and quick-exhaust valves scale the physical speed, so the number and the animation always slow down or speed up together.

Manipulation: Rotate (R), Duplicate (D or right-click), Delete (Delete), Undo (Ctrl+Z). Right-click for context menu.

Precise parameters: every slider in the properties panel is paired with a type-in number box — enter an exact value (e.g. a 63 mm bore) and press Enter; out-of-range values clamp to the component's limits automatically.

Explore provides 16+ concepts across Fundamentals (Boyle's Law, flow, force), Components (valves, cylinders, FRL), Circuits (speed control, sequencing, cascade), and Applications (pick-and-place, clamping, sorting). Formulas, worked examples, and practical tips included.

Practice offers 12 randomised problems on cylinder force, piston speed, air consumption, flow rate, valve sizing, and pressure drop with step-by-step solutions.

Quiz tests with 5 randomly selected questions from a pool of 15 covering valve types, circuit design, calculations, and ISO standards.

Annotation Toolbar: Use the marking toolbar above the canvas to annotate your circuit diagrams. Tools include Move (select, drag, resize annotations), Sketch (freehand drawing with pressure sensitivity, multiple colors and widths), and Shapes (rectangles, circles, ellipses, arrows, lines, double-arrows, and text labels).

Selection & Editing: Click any annotation to select it — a dashed selection box with corner handles appears. Drag inside the box to move, drag corners to resize, or use the action icons above the selection to rotate (15° increments), duplicate, or delete. Double-click a text label to edit it.

Zoom & Pan: Use the zoom toolbar (bottom-left) or keyboard shortcuts: Ctrl+= zoom in, Ctrl+- zoom out, Ctrl+0 reset view, Ctrl+1 fit all components. Zoom with Ctrl+Scroll (mouse) or pinch-to-zoom (touch). All elements — grid, components, connections, particles, and annotations — zoom together.

Pan Mode: Press H or right-click on empty canvas to toggle pan mode (yellow indicator on toolbar). Drag to pan the view. Press Escape to exit. Alternatively, hold Ctrl and drag to pan without entering pan mode.

Fullscreen: Click the ☶ button (top-right of canvas) for fullscreen mode with the component palette, toolbar, and readouts all visible.

Export & Toggle: Click 📷 to export the canvas as a PNG image with watermark. Use the 👁 eye icon to show/hide all annotations. Use the 🧹 Clear button to clear annotations by category (all, sketches only, or shapes & text only).

Circuit Shortcuts: Space = Run/Stop, Ctrl+Z = Undo, Ctrl+Shift+Z = Redo, R = Rotate, D = Duplicate, Delete/Backspace = Delete, Escape = Cancel.

Zoom/Pan Shortcuts: Ctrl+= = Zoom in, Ctrl+- = Zoom out, Ctrl+0 = Reset view, Ctrl+1 = Fit all components, H = Toggle pan mode, Escape = Exit pan mode.

• Always include an FRL unit between the air supply and the circuit.
• Use meter-out flow control (not meter-in) for smooth cylinder speed control — compressed air is compressible, so meter-in causes jerky motion.
• Add silencers to all exhaust ports to reduce noise in real installations.
• Use quick exhaust valves directly at cylinder ports for maximum retraction speed.
• In sequential circuits, use one-way roller levers (idle return) to avoid false signals.
• Set supply pressure to 6 bar for standard industrial pneumatic applications.
• ISO 5599 port numbering: 1=supply, 2=output A, 3=exhaust A, 4=output B, 5=exhaust B. Pilot ports follow the path they select: 12 opens 1→2 (extend), 14 opens 1→4 (retract).
• Pneumatics has no return line. Port 3 (and 5) vent to atmosphere through a silencer — there is no tank to return to, unlike hydraulics.
• Never hold a load on a closed-centre valve. ISO 4414 §5.4: air is compressible and every spool leaks, so use a pilot-operated check valve pair or a mechanical rod lock.
• Size the bore so the load ratio stays at 50–70 % of the available force, and remember the usable force is about 85 % of p × A once seal friction is counted.
• Hover over any button to see its keyboard shortcut in the tooltip.