⚡ PLC Lab

⚡ Sparky Ed

Welcome to the PLC Ladder Logic Simulator! Build and simulate industrial ladder logic circuits.

Getting Started

• Click + Add Rung to start a new rung
• Drag elements from the left palette onto rungs
• Ask me in the chat above for a circuit to build, then check your work with ✅ Check My Circuit
• Click Run (or press Space) to start scanning
• Left-click a contact to toggle it manually

Keyboard Shortcuts

• Space - Toggle Run/Stop
• Escape - Close modals/menus

Mouse Controls

• Left-click contact - Toggle manual tag state (while running)
• Right-click element - Edit or Delete context menu
• Double-click coil/element - Open edit dialog
• Click rung number - Add/edit rung comment
• + Branch button - Add parallel path to rung
• x button on branch - Delete that parallel path

Contact Types

• NO - Normally Open: closed (passes) when tag = TRUE
• NC - Normally Closed: closed (passes) when tag = FALSE
• POS - Rising edge one-shot (positive transition)
• NEG - Falling edge one-shot (negative transition)
• OL - Overload relay: NC contact, trips with Trip OL button

Coil Types

• ( ) COIL - Standard output coil, follows rung power
• ( L ) LATCH - Latches tag TRUE when rung energized
• ( U ) UNLATCH - Resets latched tag when rung energized

TON Timer

• Accumulates time while rung power is TRUE
• When accumulator reaches preset, tag_DN goes TRUE
• Resets accumulator when rung power goes FALSE

TOF Timer (off-delay)

• Starts timing when rung power drops from TRUE to FALSE
• tag_DN stays TRUE until the accumulator reaches the preset
• Used for run-on fans, motor cooldown, and purge cycles

CTU Counter (count-up)

• Counts one each time the rung goes FALSE→TRUE (a rising edge)
• When the count reaches the preset, tag_DN turns TRUE
• Drive a rung with an UNLATCH of the counter tag to reset it

OL (Overload) Relay

Use Trip OL to simulate a motor overload. The OL contact opens, stopping the motor. Use Reset OL to clear the trip and any latches.

Tag Monitor