Forward/Reverse with Relays

The same reversing circuit, but with control relays carrying the logic. This is how relay control scales toward real machine automation.

Same job, control relays in the middle

In the push-button version the Start buttons energized the contactor coils directly. In larger or automated systems you put control relays (CRs) between the operator inputs and the contactors. Buttons (or a PLC, or sensors) drive control relays; the relays’ contacts then drive the big contactor coils.

Why add relays?

• More contacts. A control relay gives several spare contacts to use elsewhere — pilot lights, interlocks, signaling other circuits — without loading the buttons.
• Separation. Operator buttons switch only a small relay coil, not the heavy contactor coil. Cleaner, safer, longer button life.
• Logic. Relays let you build conditions: run forward only if guard closed AND not in reverse AND auto-mode selected. Each condition is a contact in series.

How it is structured

Press FORWARD → control relay CRF energizes and seals in. CRF’s NO contact then energizes contactor coil F, which throws the power. The interlock now uses the relays’ NC contacts: CRF’s NC in the CRR rung and vice-versa — and the contactors are interlocked too. The reverse side mirrors it with CRR.

What to take away

Relay-driven forward/reverse puts control relays between inputs and contactors. The relays hold the logic and interlocks; the contactors do the heavy switching. Same reversing principle, a structure that scales to real machine control.