Start/Stop with Seal-In

The cornerstone circuit. Momentary Start and Stop buttons with a seal-in contact that holds the motor running after you release Start.

What you’re building

Steps

1. Add the parts

   Click Power Source, Push Button NC (your Stop), Push Button NO (your Start), Coil, NO Contact (the seal-in), Contactor (3-pole), and Motor. Spread them out.

2. Label coil, seal-in, and contactor

   Click the Coil and type M. Click the NO Contact and type M (now it follows coil M — this is your holding contact). Click the Contactor and type M.

3. Wire the main control rung

   To wire, click the first terminal (it highlights), then click the second — a wire connects them. Click empty space to deselect. Run Stop (NC) then Start (NO) in series to the coil. A1/A2 are the coil terminals.

   Power Source L1 → Stop button (left)

   Stop button (right) → Start button (left)

   Start button (right) → Coil A1

   Coil A2 → Power Source N

4. Add the seal-in around the Start button

   This is the key step. Wire the M NO Contact so it bridges across the Start button — one side ties to the wire feeding Start (the Stop-to-Start point), the other side to the wire leaving Start (the Start-to-Coil point). It sits in parallel with Start.

   Stop→Start wire (left side of Start) → M NO Contact (one side)

   M NO Contact (other side) → Start→Coil wire (right side of Start)

5. Wire the motor power

   Feed the motor through the contactor.

   Power Source L1 → Contactor T1 in

   Contactor T1 out → Motor

   Motor → Power Source N

6. Energize and test

   Click Energize. Tap Start and release — the motor keeps running, because coil M closed the seal-in contact, which now carries current around the released Start button. Tap Stop — the NC button breaks the rung, the coil drops, and the seal-in opens. Nothing restarts on its own.

7. If it doesn’t hold

   If the motor stops the instant you release Start, your seal-in is wrong: confirm the NO Contact is assigned letter M and that it’s wired in parallel with Start (across it), not in series.