Leuze electronic MLC 520 EX Series User manual

MLC 520 EX
Safety Light Curtains
SAFE IMPLEMENTATION AND OPERATION
Original operating instructions
EN 2014/12 - 50127400 We reserve the right to make technical changes

Leuze electronic MLC 520 EX 2
© 2014
Leuze electronic GmbH + Co. KG
In der Braike 1
D-73277 Owen / Germany
Phone: [phone]
Fax: [phone]
http://www.leuze.com
[email protected]

Leuze electronic MLC 520 EX 3
1 About this document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Used symbols and signal words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Checklists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1 Approved purpose and foreseeable improper operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.2 Foreseeable misuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Competent persons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Responsibility for safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Notices for the safe use of sensors in potentially explosive areas . . . . . . . . . . . . . . . . . . . 9
3 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Device overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 Connection technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3 Display elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.1 Operating indicators on the MLC 520 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.2 Alignment display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1 Start/restart interlock RES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 EDM contactor monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Transmission channel changeover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4 Range reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1 Point of operation guarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.2 Access guarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.3 Danger zone guarding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1 Arrangement of transmitter and receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1.1 Calculation of safety distance S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1.2 Calculation of safety distance SRT or SRO if protective fields act orthogonally
to the approach direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1.3 Calculation of safety distance S for parallel approach to the protective field . . . . . . . . . . 24
6.1.4 Minimum distance to reflective surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.1.5 Preventing mutual interference between adjacent devices . . . . . . . . . . . . . . . . . . . . . . . . 26
6.2 Mounting the safety sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.2.1 Suitable mounting locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.2.2 Definition of directions of movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2.3 Fastening via BT-NC60 sliding blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2.4 Fastening with BT-R swivel mount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.2.5 One-sided mounting on the machine table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.3 Mounting accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.3.1 Deflecting mirror for multiple-side guarding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
7 Electrical connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.1 Pin assignment transmitter and receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.1.1 MLC 500 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.1.2 MLC 520 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.2 Circuit diagram examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Leuze electronic MLC 520 EX 4
7.2.1 MLC 520 circuit diagram example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
8 Starting up the device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.1 Switching on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.2 Aligning the sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.3 Aligning of deflecting mirrors with the laser alignment aid. . . . . . . . . . . . . . . . . . . . . . . . . 38
8.4 Unlocking start/restart interlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
9 Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.1 Before the initial start-up and following modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.1.1 Checklist for integrator – to be performed prior to the initial start-up and
following modifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.2 To be performed periodically by competent persons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9.3 Periodically by the operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
9.3.1 Checklist – periodically by the operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
11 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1 What to do in case of error? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.2 Operating displays of the LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.3 Error messages 7-segment display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
12 Disposing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
13 Service and support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
14 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
14.1 General specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
14.2 Dimensions, weight, response time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
14.3 Dimensional drawings: Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
15 Ordering information and accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
16 EU Declaration of Conformity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

About this document
Leuze electronic MLC 520 EX 5
1 About this document
1.1 Used symbols and signal words
Table 1.1: Warning symbols and signal words
Table 1.2: Other symbols
Table 1.3: Terms and abbreviations
Symbol indicating dangers to persons
NOTICE Signal word for property damage
Indicates dangers that may result in property damage if the measures for dan-
ger avoidance are not followed.
CAUTION Signal word for minor injury
Indicates dangers that may result in minor injury if the measures for danger
avoidance are not followed.
WARNING Signal word for serious injury
Indicates dangers that may result in severe or fatal injury if the measures for
danger avoidance are not followed.
DANGER Signal word for life-threatening danger
Indicates dangers with which serious or fatal injury is imminent if the measures
for danger avoidance are not followed.
Symbol for tips
Text passages with this symbol provide you with further information.
Symbols for action steps
Text passages with this symbol instruct you to perform actions.
AOPD
Active Optoelectronic Protective Device
EDM Contactor monitoring
(External Device Monitoring)
LED LED, display element in transmitter and receiver
MLC Brief description of the safety sensor, consisting of transmitter and receiver
MTTFd
Mean Time To dangerous Failure
OSSD Safety-related switching output
(Output Signal Switching Device)
PFHd
Probability of dangerous Failure per Hour
PL Performance Level
RES
Start/REStart interlock
Scan Consecutive scans of the protective field from the first to the last beam

About this document
Leuze electronic MLC 520 EX 6
1.2 Checklists
The checklists (see chapter 9) serve as a reference for the machine manufacturer or supplier. They
replace neither testing of the complete machine or system prior to the initial start-up nor their periodic
testing by a competent person. The checklists contain minimum testing requirements. Depending on the
application, other tests may be necessary.
Safety sensor System consisting of transmitter and receiver
SIL Safety Integrity Level
State ON: device intact, OSSD switched on
OFF: device intact, OSSD switched off
Locking: device, connection or control / operation faulty, OSSD switched off
(lock-out)

Safety
Leuze electronic MLC 520 EX 7
2 Safety
Before using the safety sensor, a risk assessment must be performed according to valid standards (e.g.
EN ISO 12100, EN ISO 13849-1, IEC 61508, EN IEC 62061). The result of the risk assessment deter-
mines the required safety level of the safety sensor . For mounting, operating and testing, this document
as well as all applicable national and international standards, regulations, rules and directives must be
observed. Relevant and supplied documents must be observed, printed out and handed to affected
persons.
Before working with the safety sensor, completely read and observe the documents applicable to your
task.
In particular, the following national and international legal regulations apply for the start-up, technical
inspections and work with safety sensors:
• Machinery directive 2006/42/EC
• Low voltage directive 2006/95/EC
• EMC directive 2004/108/EC
• Use of work equipment directive 89/655/EEC supplemented by directive 95/63 EC
• OSHA 1910 Subpart O
• Safety regulations
• Accident-prevention regulations and safety rules
• Industrial safety regulation and employment protection act
• Product safety law (ProdSG)
2.1 Approved purpose and foreseeable improper operation
For safety-related information you may also contact the local authorities (e.g., industrial inspec-
torate, employer's liability insurance association, labor inspectorate, occupational safety and
health authority).
WARNING
A running machine may result in serious injury!
Make certain that the safety sensor is correctly connected and that the protective function of the pro-
tective device is ensured.
Make certain that, during all conversions, maintenance work and inspections, the system is securely
shut down and protected against being restarted.

Safety
Leuze electronic MLC 520 EX 8
2.1.1 Intended use
• The safety sensor may only be used after it has been selected in accordance with the respectively
applicable instructions and relevant standards, rules and regulations regarding labor protection and
safety at work, and after it has been installed on the machine, connected, commissioned, and
checked by a competent person (see chapter 2.2).
• When selecting the safety sensor it must be ensured that its safety-related capability meets or
exceeds the required performance level PLr ascertained in the risk assessment .
• The safety sensor protects persons or body parts at points of operation, danger zones or access
points of machines and plants.
• With the access guarding function, the safety sensor detects persons only when they enter the dan-
ger zone but cannot tell whether there are any persons inside the danger zone. For this reason, a
start/restart interlock in the safety chain is essential in this case.
• The construction of the safety sensor must not be altered. When manipulating the safety sensor, the
protective function is no longer guaranteed. Manipulating the safety sensor also voids all warranty
claims against the manufacturer of the safety sensor.
• The safety sensor must be inspected regularly by a competent person to ensure proper integration
and mounting (see chapter 2.2).
• The safety sensor must be exchanged after a maximum of 20 years. Repairs or the exchange of
parts subject to wear and tear do not extend the service life.
2.1.2 Foreseeable misuse
Any use other than that defined under the Approved purpose or which goes beyond that use is consid-
ered improper use.
In principle, the safety sensor is not suitable as a protective device for use in the following cases:
• Danger posed by ejected objects or the spraying of hot or hazardous liquids from within the danger
zone
• Applications in explosive or easily flammable atmospheres
2.2 Competent persons
Prerequisites for competent persons:
• They have a suitable technical education.
• They know the rules and regulations for labor protection, safety at work and safety technology and
can assess the safety of the machine.
• They know the instructions for the safety sensor and the machine.
• They have been instructed by the responsible person on the mounting and operation of the machine
and of the safety sensor.1
2.3 Responsibility for safety
Manufacturer and operating company must ensure that the machine and implemented safety sensor func-
tion properly and that all affected persons are adequately informed and trained.
The type and content of all imparted information must not lead to unsafe actions by users.
The manufacturer of the machine is responsible for:
• safe machine construction
• safe implementation of the safety sensor, verified by the initial test performed by a competent person
• imparting all relevant information to the operating company
• adhering to all regulations and directives for the safe starting-up of the machine
1. They perform a task related to the subject matter shortly thereafter and keep their knowledge up to date through continuous
further training.

Safety
Leuze electronic MLC 520 EX 9
The company operating the machine is responsible for:
• instructing the operator
• maintaining the safe operation of the machine
• adhering to all regulations and directives for labor protection and safety at work
• regular testing by competent persons
2.4 Disclaimer
Leuze electronic GmbH + Co. KG is not liable in the following cases:
• safety sensor is not used as intended.
• Safety notices are not adhered to.
• Reasonably foreseeable misuse is not taken into account.
• Mounting and electrical connection are not properly performed.
• Proper function is not tested (see chapter 9).
• changes (e.g., constructional) are made to the safety sensor.
2.5 Notices for the safe use of sensors in potentially explosive areas
These notices apply for devices with the following classification:
Table 2.1: Classification of the devices
Device group Device category Equipment protection
level
Zone
II 3G Gc 2 (gas)
II 3D Dc 22 (dust)
WARNING
Safe use of sensors in potentially explosive areas!
Check whether the classification of the devices corresponds to the requirements of the application.
Safe operation is only possible if the devices are used properly and for their intended purpose.
Electrical devices may endanger the health of humans and (where applicable) animals and may threat-
en the safety of goods if used under unfavorable conditions or incorrectly in potentially explosive areas.
Observe the applicable national regulations, especially ATEX directive 94/4/EC and/or EN 60079-14,
for the configuration, commissioning, operation and recurring testing of explosion-proof systems.

Device description
Leuze electronic MLC 520 EX 10
3 Device description
The safety sensors from the MLC 500 series are active opto-electronic protective devices. They satisfy the
following standards:
The safety sensors of the MLC 520 EX2 series satisfy the ATEX requirements in accordance with
EN 60079-0, EN 60079-15, EN 60079-28 for category 3G as well as EN 60079-0 and EN 60079-31 for
category 3D.
The safety sensor consists of a transmitter and a receiver (see figure 3.1). It is protected against over-
voltage and overcurrent acc. to IEC 60204-1 (safety class 3). Its infrared beams are not influenced by
ambient light (e.g. welding sparks, warning lights).
3.1 Device overview
The series is characterized by three different receiver classes (Basic, Standard, Extended) with certain
features and properties (see table 3.1).
Table 3.1: Device models in the series with specific features and functions
MLC 500
Type in accordance with EN IEC 61496 4
Category in accordance with EN ISO 13849 4
Performance Level (PL) in accordance with EN ISO 13849-1 e
Safety Integrity Level (SIL) in accordance with IEC 61508 and SILCL in
accordance with EN IEC 62061
3
Transmitter Receiver
Basic Standard Extended
MLC 500
MLC 501
MLC 500/A MLC 502 MLC 510
MLC 511
MLC 510/A MLC 520 MLC 530
OSSDs (2x) 
AS-i 
Transmission chan-
nel changeover

LED indicators 
7-segment display 
Automatic start/
restart

RES 
EDM 
Linkage 
Blanking 
Muting 
Scan mode 
Range reduction 
Test input 

Device description
Leuze electronic MLC 520 EX 11
Protective field properties
The beam distance and the number of beams are dependent on the resolution and protective field height.
Device synchronization
The synchronization of receiver and transmitter for creating a functioning protective field is done optically,
i.e. without cables, via two specially coded synchronization beams. A cycle (i.e. a pass from the first to the
last beam) is called a scan. The length of a scan determines the length of the response time and affects
the calculation of the safety distance (see chapter 6.1.1).
a Optically active area, housed in yellow
b Synchronization beams
Figure 3.1: Transmitter-receiver system
QR code
A QR code as well as the corresponding web address are located on the safety sensor (see figure 3.2).
At the web address, you will find device information and error messages (see chapter 11.3 "Error
messages 7-segment display") after scanning the QR code with a mobile end device or after entering the
web address.
When using mobile end devices, mobile service charges can accrue.
Figure 3.2: QR code with corresponding web address (URL) on the safety sensor
Depending on the resolution, the effective protective field height can be larger than the optically
active area of the safety sensor housed in yellow (see figure 3.1 and see figure 14.1).
For the correct synchronization and function of the safety sensor, at least one of the two synchro-
nization beams must be free during synchronization and operation.
a
b
b

Device description
Leuze electronic MLC 520 EX 12
3.2 Connection technology
The transmitter and receiver feature an M12 connector as an interface to the machine control with the
following number of pins:
3.3 Display elements
The display elements of the safety sensors simplify start-up and fault analysis.
3.3.1 Operating indicators on the MLC 520 receiver
Two LEDs and a 7-segment display for showing the operating state are located on the receiver:
1 LED1, red/green
2 LED2, yellow
3 OSSD icon
4 RES icon
5 7-segment display
Figure 3.3: Indicators on the MLC 520 receiver
Device models Device type Device plug
MLC 500 Transmitter 5-pin
MLC 520 Standard receiver 8-pin
13
4
2
5

Device description
Leuze electronic MLC 520 EX 13
Table 3.2: Meaning of the LEDs
7-segment display at the MLC 520 receiver
In normal operation, the 7-segment display shows the number of the selected transmission channel. In
addition, it helps during the detailed error diagnostics (see chapter 11) and serves as an alignment aid (see
chapter 8.2 "Aligning the sensor").
Table 3.3: Meaning of the 7-segment display
For error diagnostics, the error's respective letter is displayed first followed by the number code. The
display is repeated cyclically. An AutoReset is carried out after 10 s for errors that do not cause locking,
with an unauthorized restart being impossible. In the case of blocking errors, the voltage supply must be
LED Color State Description
1 Red/green OFF Device switched off
Red OSSD off
Red slowly flashing
(approx. 1 Hz)
External fault
Red flashing fast
(approx. 10 Hz)
Internal fault
Green slowly flashing
(approx. 1 Hz)
OSSD on, weak signal
Green OSSD on
2 Yellow OFF • RES deactivated
• or RES activated and enabled
• or RES blocked and protective field inter-
rupted
ON RES activated and blocked but ready to be
unlocked - protective field free
Display Description
After switching on
8 Self test
t n n Response time (t) of the receiver in milliseconds (n n)
In normal operation
C1 Transmission channel C1
C2 Transmission channel C2
For alignment
Alignment display (see table 3.4).
• Segment 1: beam area in upper third of the protective field
• Segment 2: beam area in middle third of the protective field
• Segment 3: beam area in lower third of the protective field
For error diagnostics
F… Failure, internal device error
E… Error, external error
U… Usage info, application error

Device description
Leuze electronic MLC 520 EX 14
separated and the cause of the error must be eliminated. Before switching on again, the steps taken before
initial commissioning must be repeated (see chapter 9.1).
The 7-segment display switches to alignment mode when the device has not yet been aligned or when the
protective field has been interrupted (after 5 s). In this case, a fixed beam area from the protective field is
assigned to every segment.
3.3.2 Alignment display
Approximately 5 s after a protective-field interruption, the 7-segment display switches to alignment mode.
In this mode, one third of the total protective field (top, middle, bottom) is assigned to one of the three hori-
zontal segments and the state of this sub-protective field displayed as follows:
In this mode, one third of the total protective field (Host, Middle Guest, Guest) is assigned to one of the
three horizontal segments and the state of this sub-protective field displayed as follows:
Table 3.4: Meaning of the alignment display
When the protective field has been free for about 5 s, the device switches back to the display of the oper-
ating mode.
Segment Description
Switched on All beams in the beam area are free.
flashing At least one, but not all beams in the beam area are free.
Switched off All beams in the beam area are interrupted.

Functions
Leuze electronic MLC 520 EX 15
4 Functions
An overview of features and functions of the safety sensor can be found in chapter Device description
(see chapter 3.1 "Device overview").
Overview of functions
• Start/restart interlock (RES)
•EDM
• Range reduction
• Transmission channel changeover
4.1 Start/restart interlock RES
After accessing the protective field, the start/restart interlock ensures that the safety sensor remains in the
OFF state after the protective field has been cleared. It prevents automatic release of the safety circuits
and automatic start-up of the system, e.g. if the protective field is again clear or if an interruption in the
voltage supply is restored.
Use start/restart interlock
Wire the MLC 520 receiver appropriately for the desired operating mode (see chapter 7 "Electrical con-
nection")
The start/restart interlock function is automatically activated.
Switching the safety sensor back on after shutting down (OFF state):
Press the reset button (press/release between 0.1 s and 4 s)
After the reset button has been actuated, the safety sensor switches to the ON state.
4.2 EDM contactor monitoring
The "contactor monitoring" function monitors the contactors, relays or valves connected downstream of
the safety sensor. Prerequisite for this are switching elements with positive-guided feedback contacts
(normal closed contacts).
For access guarding, the start/restart interlock function is mandatory. The protective device may
only be operated without start/restart interlock in certain exceptional cases and under certain
conditions acc. to EN ISO 12100.
WARNING
Deactivation of the start/restart interlock may result in serious injury!
Implement the start/restart interlock on the machine or in a downstream safety circuit.
The reset button must be located outside the danger zone in a safe place and give the operator
a good view of the danger zone so that he/she can check whether anyone is located in it before
pressing the reset button.
DANGER
Risk of death if start/restart is operated unintentionally!
 Ensure that the reset button for unlocking the start/restart interlock cannot be reached from the danger
zone.
 Before unlocking the start/restart interlock, make certain that no people are in the danger zone.
The contactor monitoring of the MLC 520 safety sensors can be activated through appropriate
wiring (see table 7.2)!

Functions
Leuze electronic MLC 520 EX 16
Implement the contactor monitoring function:
• through appropriate wiring of the MLC 520 safety sensors (see table 7.2).
• through the external contactor monitoring of the downstream safety relay, (e.g., MSI series from
Leuze electronic)
• or through contactor monitoring of the downstream safety PLC (optional, integrated via a safety bus)
If contactor monitoring is activated (see chapter 7 "Electrical connection"), it operates dynamically, i.e., in
addition to monitoring the closed feedback circuit every time before the OSSDs are switched on, it also
checks whether the release of the feedback circuit opened within 500 ms and, after the OSSDs are
switched off, whether it has closed again within 500 ms. If this is not the case, the OSSDs return to the
OFF state after being switched on briefly. An error message appears on the 7-segment display (E30, E31)
and the receiver switches to the fault interlock state from which it can only be returned to normal operation
by switching the supply voltage off and back on again.
4.3 Transmission channel changeover
Transmission channels are used to prevent mutual interference of safety sensors which are located close
to each other.
With the factory setting, the safety sensor works in all operating modes with transmission channel C1.
The transmission channel of the transmitter can be switched by changing the supply voltage polarity (see
chapter 7.1.1 "MLC 500 transmitter").
The transmission channel of the receiver can be switched by changing the supply voltage polarity (see
chapter 7.1.2 "MLC 520 receiver").
4.4 Range reduction
In addition to selecting the suitable transmission channels (see chapter 4.3 "Transmission channel
changeover"), the range reduction also serves to prevent mutual interference of adjacent safety sensors.
Activating the function reduces the light power of the transmitter so that around half of the nominal range
is reached.
Reducing range:
Wire pin 4 (see chapter 7.1 "Pin assignment transmitter and receiver").
The wiring of pin 4 determines the transmitting power and thereby the range.
To guarantee reliable operation, the infrared beams are modulated so they can be discerned
from the ambient light. Welding sparks or warning lights, e.g. from passing high-lift trucks, there-
by do not influence the protective field.
Faulty function due to incorrect transmission channel!
Select the same transmission channel on the transmitter and corresponding receiver.
WARNING
Impairment of the protective function due to incorrect transmitting power!
The light power emitted from the transmitter is reduced through a single channel and without safety-rele-
vant monitoring.
 Do not use this configuration option for safety purposes.
Note that the distance to reflective surfaces must always be selected so that no reflection bypass can
occur even at maximum transmitting power. (see chapter 6.1.4 "Minimum distance to reflective surfac-
es")

Applications
Leuze electronic MLC 520 EX 17
5 Applications
The safety sensor only creates square protective fields.
5.1 Point of operation guarding
Point of operation guarding for hand and finger protection is typically the most common application for this
safety sensor. In accordance with EN ISO 13855, resolutions from 14 to 40 mm make sense here. This
yields the necessary safety distance, among others (see chapter 6.1.1 "Calculation of safety distance S").
Figure 5.1: Point of operation guarding protects reaching into the danger zone, e.g. for cartoners or filling
systems
Figure 5.2: Point of operation guarding protects reaching into the danger zone, e.g. for a pick & place
robot application
5.2 Access guarding
Safety sensors with up to 90 mm resolution are used for access guarding into danger zones. They detect
people only upon entry into the danger zone, i.e., they do not detect parts of a person or whether a person
is present in the danger zone.

Applications
Leuze electronic MLC 520 EX 18
Figure 5.3: Access guarding on a transfer path
5.3 Danger zone guarding
Safety light curtains can be used in horizontal arrangement for danger zone guarding - either as stand-
alone device for presence monitoring or as stepping behind protection for presence monitoring e.g. in
combination with a vertically-arranged safety sensor. Depending on the mounting height, resolutions of
40 or 90 mm are used (see chapter 15).
Figure 5.4: Danger zone guarding on a robot

Mounting
Leuze electronic MLC 520 EX 19
6 Mounting
6.1 Arrangement of transmitter and receiver
Optical protective devices can only perform their protective function if they are mounted with adequate
safety distance. When mounting, all delay times must be taken into account, such as the response times
of the safety sensor and control elements as well as the stopping time of the machine, among others.
The following standards specify calculation formulas:
• prEN IEC 61496-2, "Active Optoelectronic Protective Devices": distance of the reflecting surfaces/
deflecting mirrors
• EN 13855, "Safety of machines - The positioning of protective equipment in respect of approach
speeds of parts of the human body": mounting situation and safety distances
6.1.1 Calculation of safety distance S
General formula for calculating the safety distance S of an optoelectronic protective device acc. to
EN ISO 13855:
S [mm] = Safety distance
K [mm/s] = Approach speed
T [s] = Total time of the delay, sum from (ta + ti + tm)
ta[s] = Response time of the protective device
ti[s] = Response time of the safety relay
tm[s] = Stopping time of the machine
C [mm] = Additional distance to the safety distance
WARNING
Improper mounting may result in serious injury!
The protective function of the safety sensor is only ensured if appropriately and professionally mounted
for the respective, intended area of application.
Only allow competent persons to install the safety sensor.
Maintain the necessary safety distances (see chapter 6.1.1).
Make sure that stepping behind, crawling under or stepping over the protective device is reliably ruled
out and reaching under, over or around is taken into account in the safety distance, if applicable with
additional distance CRO corresponding to EN ISO 13855.
Take measures to prevent that the safety sensor can be used to gain access to the danger zone, e.g.
by stepping or climbing into it.
Observe the relevant standards, regulations and these instructions.
Clean the transmitter and receiver at regular intervals: environmental conditions (see chapter 14), care
(see chapter 10).
After mounting, check the safety sensor for proper function.
In accordance with ISO 13855, with a vertical protective field, it is possible to pass under beams
over 300 mm or pass over beams under 900 mm. If the protective field is horizontal, climbing on
the safety sensor must be prevented through suitable installation or with covers and the like.
If longer stopping times are determined during regular inspections, an appropriate additional time
must be added to tm.
SKTC+=

Mounting
Leuze electronic MLC 520 EX 20
6.1.2 Calculation of safety distance SRT or SRO if protective fields act orthogonally to the approach direction
With vertical protective fields, EN ISO 13855 differentiates between
•S
RT: safety distance concerning access through the protective field
•S
RO: safety distance concerning access over the protective field
The two values are distinguished by the way additional distance C is determined:
•C
RT: from a calculation formula or as a constant, see chapter 6.1.1 "Calculation of safety distance S"
•C
RO: from a table (see table 6.1)
The larger of the two values SRT and SRO is to be used.
Calculation of safety distance SRT acc. to EN ISO 13855 when access occurs through the protective field:
Calculation of safety distance SRT for point of operation guarding
SRT [mm] = Safety distance
K [mm/s] = Approach speed for point of operation guarding with approach reaction and normal ap-
proach direction to the protective field (resolution 14 to 40 mm): 2000 mm/s or
1600 mm/s, when SRT > 500 mm
T [s] = Total time of the delay, sum from (ta + ti + tm)
ta[s] = Response time of the protective device
ti[s] = Response time of the safety relay
tm[s] = Stopping time of the machine
CRT [mm] = Additional distance for point of operation guarding with approach reaction with resolu-
tions of 14 to 40 mm, d = resolution of protective device CRT = 8  (d - 14) mm
Calculation example
The feeding-in area in a press with a stopping time (including press Safety PLC) of 190 ms is to be safe-
guarded with a safety light curtain with 20 mm of resolution and 1200 mm of protective field height. The
safety light curtain has a response time of 22 ms.
Calculate safety distance SRT using the formula acc. to EN ISO 13855.
K [mm/s] = 2000
T [s] = (0.022 + 0.190)
CRT [mm] = 8  (20 - 14)
SRT [mm] = 2000 mm/s  0.212 s + 48 mm
SRT [mm]= 472
SRT is smaller than 500 mm; this is why the calculation may not be repeated with 1600 mm/s.
Calculation of safety distance SRT for access guarding
SRT [mm] = Safety distance
K [mm/s] = Approach speed for access guarding with approach direction orthogonal to the protec-
tive field: 2000 mm/s or 1600 mm/s, if SRT > 500 mm
T [s] = Total time of the delay, sum from (ta + ti + tm)
ta[s] = Response time of the protective device
ti[s] = Response time of the safety relay
tm[s] = Stopping time of the machine
CRT [mm] = Additional distance for access guarding with approach reaction with resolutions of
14 to 40 mm, d = resolution of protective device CRT = 8  (d - 14) mm. Additional dis-
Implement the stepping behind protection required here, e.g., through the use of an additional or
cascaded safety sensor for area protection.
SRT KT C
RT
+=
SRT KT C
RT
+=
SRT KT C
RT
+=