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

2.4 SNO 4062KM input stabilization

For applications where safety carpets or mechanical contacts are prone to bounce, the input anti shake function can prevent output relay misoperation caused by brief disconnection (less than tASP). The output will only disconnect after tR if the safe input disconnect time is longer than tASP; After re closing, it still needs to go through tSP before it can be restarted. This is particularly important in situations where quick switch operations such as manual feeding can significantly reduce the mechanical wear of relays.

Wiring specifications and common errors

3.1 Power Supply and Protection

Power supply: Terminal A1/A2, AC/DC 24V, 50-60Hz.

External protection: A maximum 6A gG fuse or B/C characteristic circuit breaker must be used. The module is equipped with built-in short-circuit protection, which automatically recovers within about 3 seconds after the fault is removed.

Attention: The control output S11 is only used to connect control devices defined in this manual (such as emergency stop buttons, safety door switches, etc.), and should not be connected to external loads such as lamps, relays, or contactors.

3.2 Cross Short Detection

When enabling cross detection, wiring requirements:

CH1 (S11-S12) provides+24V signal

CH2 (S21-S22) provides 0V signal

When a short circuit occurs between two channels, the voltage is pulled low or high, and the module will detect and immediately cut off the enable output, while the electronic fuse is triggered. Common mistake on site: Connecting both channels to+24V resulted in failed cross detection. Be sure to connect according to the manual.

3.3 Feedback Circuit

Terminals S33-S34 are used to monitor the auxiliary contacts of external contactors (such as K1, K2). At startup, the module will check if the feedback loop is closed. If the external contactor is not engaged or the auxiliary contacts are not properly connected, the module will not be able to start. This is a key safety measure to prevent contactor adhesion.

Common wiring errors:

Forgot to short-circuit S33-S35 or S33-S34 (depending on startup mode).

Connected the feedback contact to other signals.

Typical application cases and parameter settings

4.1 Dual channel sliding safety door (with cross monitoring, manual start)

Wiring diagram (see top of page 4 of the PDF):

The two contacts of the safety door are respectively connected to S12 (CH1) and S22 (CH2).

Enable cross detection: S11 connected to+24V, S21 connected to 0V.

Manual start: Reset button connected to S34, S33 connected to+24V, S35 suspended or bridged to S33 (depending on specific configuration).

workflow

After power on, the safety door closes and both channels are closed.

Press the reset button (triggered by the falling edge), the module will engage, enabling contacts 13-14 and 23-24 to close, and signal contacts 31-32 to open.

The safety door opens, any channel is disconnected, and the output is immediately disconnected.

After the safety door is closed again, the reset button must be pressed again to restart.

Troubleshooting: If unable to start, check if the closing sequence of the two contacts of the safety door meets the synchronous monitoring requirements (if enabled); Measure the voltage between S12 and S11 (should be+24V), and between S22 and S21 (should be 0V). If the voltage is correct but there is no output, check if feedback loops S33-S34 are closed.

4.2 Dual channel safety carpet (with cross monitoring, manual start and reset button monitoring)

Suitable for SNO 4062KM, wiring can be found in the middle of page 4 of the PDF.

The safety carpet is a 4-wire system, with two outputs connected to CH1 (S11-S12) and CH2 (S21-S22) respectively.

Effective cross detection: When no one steps on the carpet, a short circuit path is formed, and both channels are conductive; When someone steps on the carpet, the internal structure of the carpet causes both channels to disconnect or short-circuit simultaneously.

The reset button is connected to S3 (triggered by the falling edge).

Working characteristics: Only when the safety carpet is not stepped on, it is allowed to start through the reset button. Once someone steps on the carpet, the output is immediately cut off.

Common faults:

The module cannot start when the carpet is not stepped on → Check if the carpet output resistance is<50 Ω/channel. If the resistance is too high, replace the carpet.

After stepping on the carpet, the output keeps on → Check if cross detection is enabled and if S21 is connected to 0V.

4.3 Dual channel emergency stop application (with cross monitoring, manual start)

Wiring can be found at the bottom of page 4 of the PDF.

The emergency stop button has two normally closed contacts connected to S12 and S22 respectively.

Enable cross detection, connect S11 to+24V and S21 to 0V.

Manual start, with reset button monitoring.

Safety feature: If one of the contacts is stuck (such as S12 side cannot be disconnected), when the emergency stop is pressed, the other contact S22 will still disconnect. The module recognizes that the two channel states are inconsistent (one remains high and the other becomes low), triggering the safety output to disconnect. Meanwhile, cross detection can also detect short circuits between two channels.