PEPPERL+FUCHS SLVA-4Kplus Safety Light Curtain Guide

Pepperl+Fuchs SLVA-4Kplus Safety Light Curtain Control Unit: A Comprehensive Guide from Installation to Troubleshooting

In the field of industrial automation, safety protection systems are the first line of defense to ensure the safety of personnel and equipment. Non contact electrical sensitive protective equipment (ESPD) has become the mainstream choice for entrance protection in hazardous areas due to its advantages of no mechanical wear, rapid response, and no hindrance to operation. The SLVA-4Kplus control unit launched by Pepperl+Fuchs, combined with SLA series safety light curtains or SLP series safety gratings, forms a high-performance safety light curtain system that complies with Type 4 (EN 61496-1), Category 4 (ISO 13849-1), PL e, and SIL 3 levels. This article is based on the original factory technical manual and provides a complete operation guide for automation engineers, safety system integrators, and maintenance personnel, covering product characteristics, installation wiring, mode settings, debugging steps, fault diagnosis, and regular inspections.

Chapter 1: Product Overview and System Composition

1.1 Product positioning and safety level

The SLVA-4Kplus is a control unit designed specifically for 1 to 4 single beam safety light curtains or gratings. It cannot work independently and must be used in conjunction with Pepperl+Fuchs approved SLA type light curtains or SLP type gratings. The system has reached the following security levels:

Type 4（EN 61496-1）

Category 4（ISO 13849-1）

Performance Level PL e（EN ISO 13849）

SIL 3（IEC 61508）

This means that the control system can maintain safety functions even in the event of a single failure and has self-monitoring capabilities, making it suitable for protecting high-risk machinery in hazardous areas.

1.2 System Components

A complete light curtain security system includes:

1 to 4 sets of single beam light curtains (transmitter+receiver) or SLP gratings

SLVA-4Kplus control unit

Optional: 2-channel emergency stop switch monitoring circuit

The control unit provides working power for the light curtain, drives the transmitter, and processes the receiver signal. The built-in microprocessor continuously monitors the light curtain function, and two positive directional relays (forcibly disconnect) cut off the safety output (OSSD) when the beam is obstructed. The control unit also supports DIP switch selection for multiple operating modes and can output status signals such as "ready/fault", "safety output off", "safety output on", etc.

1.3 Product Features

Self monitoring, modular structure

Monitoring relay output (EDM, external device monitoring)

Optional with/without start/restart interlock

Optional relay monitoring function

Fault diagnosis digital display, easy to locate

Protection level IP20/NEMA 1, to be installed in control cabinets above IP54

Supports up to 4 protection beams

Red visible light, easy to adjust for light

Both the receiver and control unit are equipped with stability control indicators

Can monitor 2-channel safety circuit (emergency stop circuit)

Chapter 2: Terminal Definition and Wiring Instructions

The SLVA-4Kplus adopts a screw terminal block, and all connections are completed through the front terminals. The terminal functions are shown in the following table:

Terminal Function Description

1-2 Testing/Fault Clearing: Normally open contacts must be closed during normal operation; Used for testing or fault reset

3-4 Start/restart enable normally open contacts to be closed for 0.05-1 seconds in interlock mode for startup; Keep normally open in interlock free mode

5-6 OSSD status LED direct drive can be directly connected to red/green LED (without series resistance), with a current of about 9mA; optional relay output version (2528 option)

For the connection of the 7-14 light curtain receiver or emergency stop circuit, please refer to Chapter 5 Wiring Diagram

15-16 Start ready/fault status indicator light output passive contact, requires external power supply to drive yellow indicator light

17-18 power input DC version with arbitrary polarity; Communication version has no polarity requirement

19-22 Safety Relay Output (OSSD) with two sets of normally open contacts, used to control the main circuit of the machine

23-24 Relay Monitoring Input (EDM) is only used when the relay monitoring function is enabled, in series with external relay normally closed contacts

25-32 light curtain emitter connected with two wires per channel (4 channels in total)

2.1 Fuse

The safety output is equipped with replaceable fuses: one T2.0A fuse for each of 19-20 and 21-22. Before replacing the fuse, the power supply of the control unit must be disconnected and the lower terminal block must be removed.

2.2 Cable length limit

Maximum length of cable between control unit and light curtain: 50 meters

Maximum cable length between control unit and system (such as emergency stop button): 100 meters

Chapter 3: Operation Mode Settings - Detailed Explanation of DIP Switches

The SLVA-4Kplus sets the operating mode through 4 sets of DIP switches (a total of 8 positions). It is pre-set according to the order code when it leaves the factory, and users can change it themselves. The functional verification must be completed before the system is put into use after the change. The DIP switch is located under the transparent cover on top of the control unit and can be set by prying it open with a screwdriver.

DIP switch function table

Switch position function

1+5 OFF without start/restart interlock (automatic restart)

ON with start/restart interlock (requires manual reset)

2+6 OFF without relay monitoring (EDM disabled)

ON with relay monitoring (EDM enabled)

3+7 OFF channels 3 and 4 serve as light curtain channels

ON channels 3 and 4 are used as emergency stop circuit channels

The 4+8 OFF emergency stop circuit is in static mode (24V DC level)

The ON emergency stop circuit is in pulse mode (12V pulse)

Important Notice:

When using the emergency stop circuit, the start/restart interlock (required by EN 418) must be enabled to prevent automatic restart after unlocking the emergency stop.

When using pulse emergency stop, it is necessary to ensure that DIP switches 3+7 and 4+8 are both set to ON (i.e. XX11 XX11), otherwise channel simultaneity monitoring will be lost, posing a safety hazard.

After changing the DIP switch, the control unit will immediately enter a safe state (output turned off), the 7-segment digital display will show "P", and the 15-16 terminal output will flash. All functional tests must be completed in accordance with Chapter 6 before it can be put into operation.

The modified settings should be marked in the corresponding box on the product nameplate.

Chapter 4: Installation and Wiring Specifications

4.1 Installation of control unit

The SLVA-4Kplus is installed on DIN rails (compliant with EN 50022-35 standard, 35mm wide). Insert the bottom of the control unit into the upper edge of the guide rail, then push it downwards, and the spring locking device will fix it. When disassembling, use a screwdriver to pull the locking device backwards to remove it. During installation, sufficient space should be reserved above the terminal block for inserting a screwdriver.

4.2 Wiring of Light Curtain Transmitter and Receiver

The transmitter is connected to the terminal pair by color coding:

Channel 1:25-26

Channel 2:27-28

Channel 3:29-30

Channel 4:31-32

The receiver is connected to:

Channel 1: 7-8-9

Channel 2: 7-8-10

Channel 3:11-12-13

Channel 4:11-12-14

If less than 4 channels are used, unused channels must be replaced with short-circuit wires, with a short-circuit length not exceeding 3m:

Channel 1 unused: Short circuit terminals 25 and 9

Channel 2 unused: Short circuit terminals 27 and 10

Channel 3 unused: Short circuited terminals 29 and 13

Channel 4 unused: Short circuited terminals 31 and 14

4.3 Emergency stop circuit wiring

Static emergency stop: Connect the normally open contact (or safety relay contact) of the emergency stop switch in series with the receiver input circuit of channel 3/4. Due to the loss of cross circuit monitoring, emergency stop cables must be individually armored or laid with two independent cables. The current of the emergency stop circuit is about 10 mA.

Pulse emergency stop: Connect the emergency stop switch contacts to the transmitter output and receiver input respectively, and use the short-circuit and crossover circuit monitoring functions inside the control unit, without the need for special mechanical protection for the cable. The emergency stop switch should be suitable for small loads (low current).

4.4 Wiring of indicator lights

OSSD status indicator light (red/green): connected to terminals 5-6. It can directly drive red and green LEDs in anti parallel (without resistance), with a current of about 9mA. If a larger current indicator light is needed, the 2528 option (relay output) can be selected.

Ready to start indicator light (yellow): connected to terminals 15-16 (passive contacts), requires an external 24V power supply. When this light is on, it indicates that the system is waiting for startup enable.

4.5 Safe Output (OSSD)

Terminals 19-20 and 21-22 are two independent normally open contacts without cross circuit monitoring. When connecting to the machine control system, protective cables or short-circuit protection measures should be used. The output contact voltage must meet the safety isolation requirements.

Inductive load: Users must parallel RC absorption circuits or freewheeling diodes at both ends of the contacts (note that freewheeling diodes will prolong the relay release time).

DC load: Pay attention to the contact capacity (see Chapter 7 Load Curve).

Contact switching frequency: maximum once per second.

Chapter 5: Debugging and Functional Testing

After completing the installation and wiring, follow the steps below to debug.

5.1 Optical path adjustment

The transmitter emits red visible light for easy alignment. First adjust the transmitter to align the light spot with the receiver (either by looking directly at the transmitter or using a reflector). Then adjust the angle of the receiver until its indicator light is on and the stability control is sufficient (see 2.6.3 Indicator light status).

5.2 Testing Capability

Use a test rod of the specified diameter to block each beam of light one by one, and confirm:

The output relay is turned off, and the OSSD indicator light changes from green to red.

The corresponding channel receiving indicator light on the control unit is off.

All beams can reliably trigger safe outputs.

5.3 Start/restart interlock test (if enabled)

Block a beam of light and then clear all beams.

The output relay should remain off (interlock effective), and the yellow start ready indicator light should light up.

Press the start button (short-circuit terminals 3-4, 0.05~1 second).

The output relay should be turned on, and the yellow indicator light should be off.

5.4 Test Input Function

Ensure that all beams are unobstructed. If in interlock mode, perform the startup enable first to turn on the output.

Short circuit terminals 1-2 (test input).

The output relay should be immediately turned off; After disconnecting the short circuit, the system should be reset and restarted.

5.5 Relay monitoring function test (if enabled)

Disconnect terminal 23 or 24.

Power on the control unit.

The digital display should show ". F", indicating that the relay monitoring is activated.

The fault was resolved after reconnection.

5.6 Static emergency stop test

Close all emergency stop switches, ensure the beam is unobstructed, execute the start enable, and the safety output should be turned on.

Operate any emergency stop switch (disconnect circuit), the safety output should be immediately turned off, and the digital display should not show any faults.

Repeat the test for each emergency stop switch.

5.7 Pulse Emergency Stop Test

The method is the same as static emergency stop, but additionally confirm that the DIP switch is in position XX11 XX11.

Chapter 6: Indicator lights and fault diagnosis

6.1 Internal indicator lights of control unit

LED/Display Meaning

OSSD red safety output shutdown

OSSD green safety output connected

E1-E4 yellow constant light corresponds to smooth channel beam

E1-E4 yellow flashing beam is unobstructed but lacks stability reserve

E1-E4 extinguishing beam obstructed or emergency stop circuit disconnected

7-segment digital tube clockwise scrolling light protection area is unobstructed, OSSD is turned on (running light)

The digital display shows that the protected area of "0" is obstructed

The digital display shows that the "1" protection area is unobstructed but OSSD is turned off, waiting for startup

The digital display shows "2" system malfunction

The digital display shows that the "P" DIP switch is set incorrectly or is currently being set

The digital display shows that the "E" transmitter is short circuited or the receiver is faulty

The digital display shows "F" external relay fault (relay monitoring)

The digital display shows a synchronous fault in the "8" emergency stop channel

Digital tube decimal point flashing fault status

6.2 Common Troubleshooting

Possible causes of malfunction, operator actions

All components have no indicator lights, power failure check, power supply

External OSSD indicator light does not light up, wiring error or LED damage. Check wiring

The start ready indicator light is not on, and there is a wiring problem. Check terminals 15-16

The activation of the ineffective beam is obstructed; Or check the E1-E4 indicator lights for wiring errors of the start button; If the start ready light is on, check the button circuit

Digital tube displays "2" transmitter installation issue. Check the wiring and alignment of the transmitter

The digital display shows that the "F" relay monitoring circuit is disconnected. Check the external relay and its normally closed contact series circuit

The digital display shows "0" and cannot clear the obstruction of the light beam or the disconnection of the emergency stop circuit. Check the corresponding channel receiving indication; If it is in emergency stop mode, check the status of the emergency stop switch

The digital display shows a short circuit in the "E" receiver or interference from adjacent light curtains. Check the wiring of the receiver; Ensure that the light curtains of different control units do not illuminate each other

An output cannot be connected, and the fuse is blown. Check and replace the T2A fuse

Check the contact of the emergency stop switch for the simultaneous loss of the "8" emergency stop channel displayed on the digital display; If pulse mode is used but DIP is set to static, the settings need to be changed

Note: In high-frequency electromagnetic fields (>10 V/m), the SLVA-4Kplus output may accidentally switch to a safe state.

Chapter 7: Summary of Technical Data

7.1 Security Level

Type 4 (EN 61496-1)

Category 4 (EN ISO 13849-1)

PL e

SIL 3 (IEC 61508)

7.2 Electrical Data

Power version, voltage range, power consumption, current consumption

230VAC 195~253VAC, 48~62Hz 13W ≤50mA

115VAC 98~127VAC, 48~62Hz 13W ≤100mA

24VDC 20.4~27.6VDC 7W ≤220mA

24VAC/DC (2528) 21.6~26.4VAC/DC 7W ≤220mA

Response time: 40 ms (fixed)

Start enable/fault reset signal duration: 0.05~1 second

Relay monitoring detection delay: 200 ms

Emergency stop simultaneous fault detection delay: 2 seconds

7.3 Safety output contact capacity

Switching voltage: 20-230V AC/DC

Switching current AC: 0.01~2A

Switching current DC: Refer to the load curve (resistive load approximately 2A/24VDC, inductive load requires derating)

Contact protection: Internal T2A fuse

Switching frequency: maximum once per second

7.4 Environmental conditions

Working temperature: 0~50 ℃

Storage temperature: -20~75 ℃

Humidity: ≤ 95% (20~50 ℃)

Protection level: IP20/NEMA 1 (must be installed in cabinets with IP54 or higher)

Weight: Approximately 900g

Chapter 8: Calculation of Safety Distance and Installation Height

According to ISO 13855 (formerly EN 999), the minimum safe distance S for a light curtain is calculated using the following formula:

S = K × T + C

among which

S: Minimum distance between the boundary of the hazardous area and the boundary of the protected area (mm)

K: Approaching the velocity constant (usually taken as 1600 mm/s or 2000 mm/s)

T=t1+t2: total response time, t1=protective equipment response time (40ms), t2=machine shutdown time

C: Additional distance, usually set at 850 mm for entrance and exit protection

For multi beam gratings, the recommended installation height (from the reference plane) according to ISO 13855 is:

Number of beams and height (mm)

2 bundles of 400 and 900

3 bundles of 300, 700, 1100

4 bundles of 300, 600, 900, 1200

In addition, it should be noted that there should be no reflective objects (such as metal walls) within the range of the light cone of the transmitter/receiver, otherwise it may cause light to bypass obstacles (reflections) and cannot be reliably detected.

Chapter 9: Regular Inspection and Maintenance

To ensure the long-term effectiveness of safety functions, regular inspections must be carried out. If it is not possible to ensure at least one penetration test of the protected area per day, or if the equipment is not turned on and off once a day, the following output relay checks must be performed:

Clear the protected area, perform startup enable (if necessary), and turn on the safety output.

Block any beam of light and observe the control unit or external indicator light changing from green to red.

If the system has not entered a fault state, the inspection has passed; If there is a fault display, troubleshoot and repeat the inspection.

In addition, the protection area should be penetrated at least once during daily operations to confirm that the system can correctly turn off the output.

Chapter 10: Ordering Information

SLVA-4Kplus offers multiple power versions and functional combinations:

Power supply without AWS/RM only AWS only RM AWS+RM

24VDC SLVA-4Kplus 24VDC …-RI …-RM …-RI,RM

115VAC SLVA-4Kplus 115VAC …-RI …-RM …-RI,RM

230VAC SLVA-4Kplus 230VAC …-RI …-RM …-RI,RM

2528 option (relay output instead of LED driver):

SLVA-4Kplus-2528 24VAC/DC

SLVA-4Kplus-2528 115VAC

SLVA-4Kplus-2528 230VAC

AWS=Start/Restart Interlock, RM=Relay Monitoring. The default AWS setting at the factory is ON (with interlock).

Chapter 11: Circuit Examples

Example 1: 4-channel light curtain+start interlock+relay monitoring

DIP switch settings: 1=ON, 5=ON (AWS); 2=ON, 6=ON（RM）； 3=OFF, 7=OFF (light curtain); 4/8 is arbitrary. Refer to Figure 10.1 for wiring.

Example 2: 2-channel light curtain+static emergency stop

DIP switch: 3=ON, 7=ON (emergency stop channel); 4=OFF, 8=OFF (static); AWS and RM are set up on demand. The emergency stop cable requires mechanical protection. Refer to Figure 10.2 for wiring.

Example 3: 2-channel light curtain+pulse emergency stop

DIP switch: 3=ON, 7=ON; 4=ON, 8=ON (pulse). The emergency stop cable does not require special protection, but the emergency stop switch must be suitable for low current switching. Refer to Figure 10.3 for wiring.