Ladder logic builder

Devices & instructions

Start from the devices you'd wire in real life — pushbuttons, floats, limit switches, motor starters, horns, internal relays. Every rung reads left to right: contacts pass or block power, the output at the right acts on the result. -| |- (NO) conducts while its bit is ON; -|/|- (NC) while OFF — the device is the bit, the contact type is how the rung asks about it, exactly like real hardware.

Real stop buttons, e-stops and overload relays are wired normally closed, so a broken wire stops the machine. Tap NO on any input device to wire it NC: it then reads 1 at rest and drops to 0 when you press or trip it. The overload relay comes wired that way — healthy is 1, tripped is 0 — so the rung that stops the motor examines it the way you would in Studio 5000.

Coils: OTE follows the rung, OTL/OTU latch and unlatch a bit that stays, OSR turns its bit on for exactly one scan each time the rung goes true — the one-shot. Timers: TON delays the on, TOF holds the off, RTO remembers its accumulator until a RES clears it. Counters CTU/CTD count rising edges up or down and fire their done bit at the preset. The scan runs top to bottom, over and over — order matters. It's the same live scan as the guided simulator.

Branches

An OR groupcan sit anywhere in the rung — wrap one around just the Start button (∥+ on a contact) and you've built the classic seal-in — and a branch can be a series of contacts, like a jog path that needs manual mode AND the jog switch at once. Branches also nest: ∥+ on a contact inside a branch opens a sub-branch around just that segment — the exact topology of real Logix prints.

A rung can also drive parallel outputs(+ output): every coil or box on the rung sees the same condition, the way Logix prints put a motor and its pilot light on one rung. You'll hear "one output per rung" in class — that's a teaching convention, not a hardware rule.

Machines

Wire your rungs to a machine — a tank with float switches, a conveyor with a photo-eye, a press with limit switches at both ends of the stroke. The machine answers your outputs with real inputs, so the circuit stops waiting for you to play the part of the process: press nothing and watch it cycle on its own.

Editing

Edit right on the diagram: tap a contact, compare, output, branch leg, or rung number to change it in place. Drag a contact to move it, and press-hold a rung number to move the whole rung (on a phone, hold a moment to lift; scrolling still just scrolls). Branches, groups and whole rungs can all be rearranged, and the ↤ / ↦ controls on a group stretchits legs over the neighboring contacts — the same adjustment you'd make in Logix by dragging a branch's vertical wire.

The whole circuit lives in the link: share the URL and your circuit arrives running.