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Build Guide · Motor Control

Forward / Reverse (Relays)

The same reversing job, but with control relays carrying the logic and interlocks, and the contactors doing only the power switching.

Difficulty: AdvancedBuilds on: forward/reverse with buttonsLesson: read the theory →

What you’re building

L1L2/NSTOPFWDCRRCRFCRFREVCRFCRRCRFF(a matching CRR contact drives contactor coil R)
Control relays CRF/CRR hold the logic. Each seal-in brackets its own button only, leaving the interlock NC contact in series so it can never be bypassed. The relay contacts then drive the contactor coils F/R.

Parts to add

  • 1Power Source (3-phase)
  • 1Push Button NC (Stop)
  • 2Push Button NO
  • 2Coil (control relays)
  • 2NO Contact (seal-ins)
  • 2NC Contact (interlocks)
  • 2Coil (contactor coils)
  • 2NO Contact (relay→contactor)
  • 2Contactor
  • 1Motor

Steps

  1. Add the parts

    Same as the button version, but add two extra Coil for the control relays and two extra NO Contact to drive the contactor coils. Set the Power Source to 3-phase.

  2. Label the two layers

    Control relays = CRF and CRR. Contactor coils = F and R. Seal-in NO contacts = CRF / CRR. Interlock NC contacts = CRF / CRR. The relay-to-contactor NO contacts = CRF / CRR.

  3. Build the relay logic rungs

    Exactly like forward/reverse buttons — shared Stop, interlocked through each other’s NC contacts, each with its own seal-in — but energizing the control relays CRF and CRR (not the contactors).

    Stop → Fwd button → NC(CRR) → Coil CRF (+ CRF seal-in across Fwd)
    Stop → Rev button → NC(CRF) → Coil CRR (+ CRR seal-in across Rev)

  4. Let the relays drive the contactors

    A NO contact from each relay energizes its contactor coil.

    Power Source L1 → NO Contact CRF (left)
    NO Contact CRF (right) → Coil F A1
    Power Source L1 → NO Contact CRR → Coil R

  5. Wire the contactors to the motor

    Contactor F straight; Contactor R with two legs swapped — same as before.

    Contactor F → straight through → Motor
    Contactor R → two legs swapped → Motor

  6. Energize and run

    Click Energize and operate Forward/Reverse. Notice the logic (relays) and the action (contactors) are now separate layers — exactly how relay control scales toward a PLC.

✓ Test it

  • Forward: CRF seals in, which energizes contactor F, which runs the motor forward.
  • Reverse mirrors it through CRR and contactor R.
  • The decision lives in the relays; the power switching lives in the contactors.
Tip: This split — relays decide, contactors act — is exactly how relay logic scales up, and how a PLC thinks in software.

Open the Sandbox and build it

Follow the steps above with the trainer open in another tab.

Open the Sandbox →
← Forward / Reverse (Buttons)Next: Jogging (Inch Control) →