SNO 4062K/SNO 4062KM Safety Relay On site Troubleshooting and Selection Replacement Guide

SNO 4062K/SNO 4062KM Safety Relay On site Troubleshooting and Selection Replacement Guide

In the safety control circuit of industrial machinery and equipment, emergency stop monitoring and protective door interlocking are the most basic and important functions. The SNO 4062K and SNO 4062KM series safety relay modules are designed for single or dual channel emergency stop monitoring in accordance with DIN EN 60204-1 and EN ISO 13849-1, with a maximum capacity of PL e, Class 4, and SILCL 3 (according to DIN EN 62061). This series of products is widely used in fields such as stamping machinery, automated production lines, robot workstations, and packaging equipment. However, due to on-site electromagnetic interference, wiring errors, contact wear, or external sensor failures, these safety relays may experience typical issues such as inability to start, non functioning output contacts, and flashing LED alarms. This article is based on official technical information and combined with actual maintenance experience to systematically sort out the selection points, typical fault diagnosis, and standardized troubleshooting methods of SNO 4062K/KM, helping on-site engineers quickly restore equipment safety functions.

Product Series Overview and Model Differences

SNO 4062K and SNO 4062KM are both basic safety switch units with built-in forced pilot relays and self-monitoring for each ON-OFF cycle. Both provide two enable contacts (13-14, 23-24) and one signal contact (31-32), supporting manual or automatic start, optional with/without cross short circuit detection, and feedback loop with external contactor monitoring (S33-S34). The core differences between the two are as follows:

Characteristics SNO 4062K SNO 4062KM

Synchronous monitoring supports dual channel synchronous time monitoring (tS), requiring CH1 to close before CH2 without synchronous monitoring function

Suitable for input devices such as emergency stop buttons, safety door switches, and light curtain OSSD outputs. In addition to the above, it is also suitable for safety carpets (4-wire system, no monitoring resistors)

Input debouncing is absent to prevent frequent switching of output relays due to rapid on-off of input signals

Typical applications include emergency stop, safety doors, light curtains, safety carpets, and frequent manual operations (such as manual feeding)

Ordering information:

Model Rated Voltage Wiring Method Order Number

SNO 4062K AC/DC 24V 50-60Hz cage spring terminal R1.188.0699.2

SNO 4062K-A AC/DC 24V 50-60Hz pluggable connector R1.188.0709.2

SNO 4062KM AC/DC 24V 50-60Hz cage spring terminal R1.188.0719.2

SNO 4062KM-A AC/DC 24V 50-60Hz pluggable connector R1.188.0729.2

Selection suggestion: If you need to monitor safety carpets or have frequent and rapid on-off conditions (such as jog operation during manual feeding), you should choose SNO 4062KM to utilize its input anti shake function. If the device requires time monitoring due to synchronization requirements (such as protective doors must be opened and closed in a specific order), SNO 4062K should be selected.

Detailed explanation of core functions and working modes

2.1 Basic working principle

After power on, supply power to the module through terminals A1/A2. When both safety input channels (CH1, CH2) are closed, the internal forced pilot relay is activated through a reset input (manual or automatic start) to enable the output contacts to close. When any safety input is disconnected, the enable contact immediately disconnects, cutting off the power source in the hazardous area.

2.2 Operating Mode Settings

According to on-site requirements, the following modes can be configured through external wiring:

Explanation of Mode Wiring Method

Single channel control with parallel connection of two safety channels (S12 and S31 short circuited to S11) is not recommended for high safety levels

Dual channel non crossing detection S12 and S31 are connected to high level (+24V), and S11 is connected to the common terminal without line short circuit monitoring

Dual channel with cross detection CH1 connected to positive potential (S11-S12) and CH2 connected to negative potential (S21-S22) can detect short circuits between the two channels

Manual start (with reset button monitoring), connect to the reset button (triggered by the falling edge) in S3; Press the button to connect the bridge from S35 to S33 or suspend it for each startup

Automatically start the short circuit between S35 and S33, and the unit does not require manual reset to start on the rising edge when the safety input is closed

Even if the safety input is closed, the startup lock will not start after power on. The reset button must be pressed to prevent automatic operation when powered on

After the safety input is disconnected and then closed, it will not automatically restart. The reset button needs to be pressed to meet higher safety standards

2.3 Synchronization Monitoring of SNO 4062K

When dual channel control is enabled and synchronous monitoring is enabled, it is required that the safety channel CH1 must be closed before CH2, and the time difference between the two closures cannot exceed the synchronization time tS. If CH2 closes before CH1, synchronous monitoring will be triggered, and the enable circuit cannot be closed. Common on-site problem: Connecting the two sets of contacts of the emergency stop button in reverse order during wiring, resulting in the module being unable to start. The solution is to check the switching sequence of the two channels or disable synchronous monitoring by short circuiting S33/S35 (see wiring diagram for details).