Schmersal de 42279 Wiring Diagram and Installation Guide
Secure the unit to a vibration-free steel panel with M4 bolts torqued to 1.2 Nm; this eliminates micro-movement that may cause unintended shutdowns.
Feed a regulated 24 V DC line to terminal 1 only after confirming the supply is de-energised. Apply a tightening force of 0.6 Nm to each clamp and use 0.5 – 1.5 mm² ferruled conductors to achieve reliable strain relief.
Adopt the standard colour legend–brown for +24 V, blue for 0 V, black for status output, white for auxiliary–while keeping sensor cores separated from motor feeders by at least 100 mm to curb inductive noise. Maintain a cable-bend radius no smaller than five times the sheath diameter.
The enclosure carries an IP66 seal; therefore, set the M12 gland to 1.5 Nm and ensure the elastomer washer sits flush, preserving the ingress rating even under high-pressure wash-down.
For series-linked emergency-stop loops, route all normally-closed contacts in sequence and confirm total loop resistance below 10 Ω to satisfy ISO 13849-1 Performance Level e. Finish by logging the insulation-test readings (500 V DC for 1 min) to document compliance.
Detailed Connection Layout for DE-Series Safety Switch
Route the control circuit through terminals 13 and 14 (normally closed) to guarantee an immediate stop of hazardous motion once the guard opens.
Power conductors should enter via the M20 gland; employ fine-strand copper, 0.75–1.5 mm², rated for 600 V. Strip insulation to 7 mm so strands sit flush inside the spring clamp–no copper left exposed.
Auxiliary signalling is provided on terminals 23 (common) and 24 (normally open). Wire this pair to the PLC status input to record door position without influencing the safety loop.
Attach the protective earth to the marked PE lug and torque the screw to 1.2 N·m; this keeps fault-path impedance under 0.1 Ω.
Cascading units? Bridge terminal 14 of the first switch to terminal 13 of the next with a shielded, twisted pair; maintain loop resistance below 50 mΩ.
For cable runs exceeding 30 m, install a 0.1 µF suppression capacitor across the coil supply at the control cabinet to damp contact-bounce transients.
After completing connections, megger-test continuity: closed contacts must read 0 Ω, open ones ≥1 MΩ at 500 V DC.
Pin Assignment and Terminal Identification
Feed Pin 1 with a stabilised 24 V DC supply before terminating any other conductor to guarantee proper lock engagement.
- 1 – A1 (24 V DC +): brown lead – primary power for the internal actuator.
- 2 – X1 (Guard Input 1): white – first safety-channel input.
- 3 – A2 (0 V): blue – common reference for all control lines.
- 4 – Y1 (Guard Output 1): black – first p-type OSSD feedback (≤ 0.25 A).
- 5 – OUT (Diagnostic): grey – serial status signal; leave open if the gateway is absent.
- 6 – X2 (Guard Input 2): violet – second safety-channel input for category 4/PL e circuits.
- 7 – Y2 (Guard Output 2): red – second OSSD feedback mirroring Y1.
- 8 – IN (Diag Return): pink – receives diagnostic data from the previous unit; terminate on the first sensor in a chain.
- Route the 8-core cable in its own conduit, well clear of motor feeders, to minimise inductive noise.
- Crimp ferrules on every lead and tighten the M12 A-coded plug to 0.4 Nm for IP67 integrity.
- Configure the safety PLC test-pulse interval to ≥ 100 ms to match the sensor’s input tolerance.
- For series networks of up to 31 units, verify ≥ 20.4 V remains at the most distant device to avoid brown-outs.
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Safety Relay Integration Steps Within Control Circuits
Install a relay certified to at least SIL 3 / PL e according to the machine’s risk assessment, ensuring its summation current does not exceed 5 A at 24 V DC.
Separate all control conductors from power lines by ≥ 3 mm and route them in shielded cable trays to minimise electromagnetic interference and crosstalk.
Connect dual-channel E-stop and guard interlock contacts to the relay’s redundant inputs, observing NC–NO sequencing to match the selected stop category (0 for immediate power removal, 1 for controlled deceleration).
Close the feedback loop through the main contactor’s auxiliary NC contact on terminals Y1–Y2; measure loop resistance and keep it below 100 Ω to prevent fault masking.
Wire the manual reset push-button to terminals S33–S34 with monitored start; set debounce filtering ≤ 30 ms so that bounce cannot spoof a valid reset.
Configure cross-fault detection by enabling the relay’s internal pulse-checking feature; verify that both input channels register a fault within 100 ms if a short occurs between conductors.
Run a functional test: trigger the E-stop and confirm de-energisation within ≤ 20 ms, then record the measured stop time in the validation log in accordance with ISO 13849-2.
Document circuit routing, safety calculations (MTTFd, DCavg), and validation data in the technical file; schedule inspection every 12 months or 10 000 cycles, whichever comes first, replacing the relay once contact wear exceeds 15 mΩ.
Troubleshooting Common Wiring Faults and Diagnostics
Immediately check continuity across terminal pairs using a multimeter. For example, test between pins 13 and 14; an open circuit here indicates a failed contact or mechanical misalignment in the actuator.
Verify proper voltage levels at supply terminals–typically 24V DC. Readings significantly lower suggest power supply degradation or resistance due to poor connections.
Inspect ground reference integrity. An unstable or floating ground can cause erratic behavior. Use a scope to detect voltage fluctuations relative to chassis ground.
Examine contact bounce with an oscilloscope. Excessive signal jitter across normally open outputs indicates worn internal elements or contamination on switching surfaces.
Check logic inversion errors in downstream PLC input mapping. An N.C. contact read as high could be misinterpreted unless software debouncing and signal logic are configured correctly.
Test safety chain response by manually engaging and disengaging actuator. Delay in output state changes implies sluggish relay response or residual capacitance on input circuits.
Scan for cross-talk in adjacent conductors, especially when routed in parallel with motor cables. Use shielded cables or separate routing to reduce interference-related faults.
Always confirm component ratings match the control system’s current and voltage demands. Overloaded terminals or incompatible devices often cause intermittent loss of signal integrity.