Emergency Stop & Safety Relay Wiring Diagram — the Complete Circuit, Terminal by Terminal

Content updated: September 6, 2026. Functional diagrams below replace inconsistent legacy terminal illustrations; they are not installation drawings.

How Do an E-Stop Button and a Safety Relay Work Together?

An emergency-stop button initiates a stop command; it does not by itself evaluate wiring faults, monitor downstream contactors or manage restart. Those functions belong to the chosen safety-control architecture. An emergency stop is a complementary protective measure, not a substitute for guards or other required safeguards.

A light curtain usually supplies self-tested OSSD signals, whereas an emergency-stop button supplies passive contacts. These are different input interfaces: the evaluation device must explicitly support the selected mode. The DA31 product specification lists input modes, but terminal connections, test-pulse behaviour and fault detection require the applicable manual. The light curtain wiring guide covers the OSSD variant; this page focuses on the button circuit.

Inside the Button: Why Two NC Contacts?

A dual-channel example uses two suitable normally-closed, positive-opening contact blocks operated by the emergency-stop actuator. The required number and architecture follow the risk assessment and applicable machine requirements. Positive opening uses mechanical actuator force to open the contact; it does not eliminate every wiring or installation fault. Releasing the latched button must not itself restart hazardous motion.

Separate channels can support fault detection and continued stopping after specified faults, but do not guarantee detection of every short. Cross-circuit detection depends on the relay input design, pulse sources, wiring and operating mode. A common cable damage event may affect both channels; assess routing, protection and justified fault exclusions in the actual design.

The Complete Circuit: E-Stop → Safety Relay → Contactors

The DA31 specification lists 24 V DC supply and three safety N.O. contact pairs: 13/14, 23/24 and 33/34; 41/42 is an auxiliary N.C. signalling contact, not an additional safety output. A redundant contactor architecture may use separate safety contacts to control K1 and K2, with their main contacts arranged to remove the hazardous energy as designed. Select contactors, coil suppression and utilization-category ratings from the actual load. The listed 5 A gL/gG external output fuse is not evidence for specifying a 5 A fuse in the relay supply leg; size supply protection separately from the approved manual and wiring design.

The published DA31 release response below 30 ms describes input-to-output response, not the time for the machine to stop. Include contactor or drive response and machine stopping time in the complete function. Contact load ratings depend on utilization category; an AC-1 value must not be used as an AC-15 or DC-13 coil-switching rating.

Wiring Multiple E-Stop Buttons in One Circuit

Where the manufacturer-approved design permits series connection, a line may chain its buttons: every station's channel-1 contact in one loop into S1, every channel-2 contact in a second loop into S2, in the same station order. Any button pressed opens both loops and commands the defined stop zone; determine that zone in the machine risk assessment. Assess fault masking and diagnostic limitations. The trade-offs are physical and diagnostic: long series loops accumulate line resistance (check it against the relay's input specification before committing a 60-metre run), and a series loop cannot tell the maintenance team which station tripped. Long lines therefore add a per-zone status contact into the PLC, or move to individually monitored inputs, as required by the chosen architecture. Ordinary status indications do not replace safety evaluation.

Reset Modes: Manual vs Automatic Re-Arming

Distinguish button release, safety-output re-arming and machine restart. The Pilz emergency-stop guidance explains that resetting the operated device may only prepare for restart, not start the machine. DA31 restart wiring and any monitored-reset behaviour must be verified in the applicable manual; a simple manual input is not proof of edge or stuck-button monitoring. The functional reset sequence below deliberately omits jumper states and terminal pinouts; these must come from the applicable manual.

EDM Feedback: Making the Circuit Notice a Welded Contactor

EDM monitors the external switching elements. In a contactor example, suitable designated N.C. mirror contacts return the released state to a documented monitoring circuit. A generic auxiliary contact does not necessarily prove the position of the main contacts. With an approved feedback design, failure to reach the expected state prevents the next enable. This external check is separate from the force-guided contacts inside the relay.

DA31 EDM capability and terminal details are not established by the currently cited specification. Do not assume that requesting an EDM drawing means the feature exists. Obtain an applicable manufacturer-approved solution, or select a relay/controller with the required documented monitoring. The EDM feedback examples explain the generic diagnostic purpose, not an approved DA31 circuit.

Connecting Brand Safety Relays: the Universal Checkpoints

A Pilz PNOZ, Guardmaster, Siemens 3SK and DA31 can differ in their supported safety functions as well as terminal names. Use the five checkpoints below as questions for both manuals, not as terminal equivalences. An unsupported input, monitored-reset or feedback function prevents a simple rewiring substitution.

• Supply naming: A1/A2 on most European relays equals the DA31's (+)/(0V) — confirm voltage and polarity, not just position.
• Channel circuits: trace the source and return for each channel in the exact manual; S11/S12 and S1/S2 are not interchangeable terminal assignments.
• Reset behaviour: verify start/restart interlocking, permitted button wiring and edge monitoring; do not transfer terminal labels across models.
• Feedback/EDM naming: often Y1–Y2 or an S34 loop — never assume it is optional just because the demo wiring omitted it.
• Coil ratings: verify the exact safety and auxiliary contact pairs and utilization-category ratings. Similar numbering is not a guarantee of the same function or coil-switching capacity.

Function-level comparisons of the DA31 against Pilz PNOZ, Allen-Bradley Guardmaster and Siemens SIRIUS 3SK relays live on their own pages, including when a configurable controller is the better answer than any hardwired relay.

The Six E-Stop Wiring Mistakes We Actually See

• Changing the approved input architecture — omitting a required channel or diagnostic path changes the safety design; validate the specified arrangement.
• Two contacts merged onto one conductor — electrically one channel wearing two connectors; a single short defeats both.
• A maintained switch on the reset input — taped-down or selector-style reset can defeat the intended reset behaviour; its consequences depend on the validated architecture. Reset and machine restart must remain distinct.
• Missing required output monitoring — where the safety design relies on contactor feedback, verify the monitoring circuit and suitable mirror contacts.
• Misapplied protection — output-contact fusing and supply-circuit protection serve different purposes; use each applicable rating rather than copying one fuse value everywhere.
• Using 41/42 as a safety contact — it is a status auxiliary; the safety path runs through the force-guided NO contacts only.

Commissioning: the Test That Makes It Real

A competent person should commission the circuit under an approved, controlled validation procedure: inspect wiring with hazardous energies isolated; verify each station commands the required stop; confirm release, power restoration and reset cannot cause an unintended restart; and verify the specified fault responses without exposing anyone to motion. For a documented EDM circuit, failure to complete the feedback path must prevent enabling. Never bypass or short a feedback contact as a claimed welded-contactor test: that can mask the fault. Use only the manufacturer-approved simulation method with hazardous motion prevented, then restore and independently check the circuit. Record the schematic/manual revisions, expected and actual results, tester and outstanding defects.

For the light-curtain leg of the same cabinet, the complete light curtain wiring diagram library is the companion to this page. Legacy downloads must be checked against their revision and current device instructions, not treated as an approved circuit.