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T7F-2
Installation Manual
MAEN181, 2015-03
English
Foreword
Installation manual for T7F-2
Foreword
All are developed to satisfy the demands of human-machine communication.
Built-in functions such as displaying and controlling text, dynamic indication,
time channels, alarm and recipe handling are included.
The operator panel works primarily in an object-oriented way, making it easy to
understand and use. Configuration is carried out on a PC using the iX Developer.
The project can then be transferred and stored in the operator panel itself.
Various types of automation equipment such as PLCs, servos or drives can be
connected to the . In this manual, the term “the controller” refers to the connected
equipment.
This manual explains how to install the operator panel. Please refer to the
iX Developer reference manual for further information.
Order no: MAEN181
Copyright © 2015-03 Beijer Electronics AB. All rights reserved.
The information in this document is subject to change without notice and is provided as available at the
time of printing. Beijer Electronics AB, including all its group companies, reserves the right to change any
information without updating this publication. Beijer Electronics AB, including all its group companies,
assumes no responsibility for any errors that may appear in this document. Read the entire installation
manual prior to installing and using this equipment. Only qualified personnel may install, operate or repair
this equipment. Beijer Electronics AB, including all its group companies, are not responsible for modified,
altered or renovated equipment. Because the equipment has a wide range of applications, users must acquire
the appropriate knowledge to use the equipment properly in their specific applications. Persons responsible
for the application and the equipment must themselves ensure that each application is in compliance with
all relevant requirements, standards and legislation in respect to configuration and safety. Only parts and
accessories manufactured according to specifications set by Beijer Electronics AB, including all its group
companies, may be used.
BEIJER ELECTRONICS AB, INCLUDING ALL ITS GROUP
COMPANIES, SHALL NOT BE LIABLE TO ANYONE FOR ANY
DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL
DAMAGES RESULTING FROM THE INSTALLATION, USE OR
REPAIR OF THIS EQUIPMENT, WHETHER ARISING IN TORT,
CONTRACT, OR OTHERWISE. BUYER'S SOLE REMEDY SHALL
BE THE REPAIR, REPLACEMENT, OR REFUND OF PURCHASE
PRICE, AND THE CHOICE OF THE APPLICABLE REMEDY SHALL
BE AT THE SOLE DISCRETION OF BEIJER ELECTRONICS AB,
INCLUDING ALL ITS GROUP COMPANIES.
Beijer Electronics, MAEN181
Contents
Contents
1 Safety Precautions .......................................................
1.1
General ...........................................................
1.2
During Installation ..............................................
1.3
During Use .......................................................
1.4
Service and Maintenance ........................................
1.5
Dismantling and Scrapping .....................................
1.6
Appearance of Air in Touch Screen .............................
2 Installation ...............................................................
2.1
Space Requirements .............................................
2.2
Installation Process ..............................................
2.2.1
2.2.2
Connections to the Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Other Connections and Peripherals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Technical Data ...........................................................
4 Chemical Resistance ....................................................
4.1
Plastic Casing ....................................................
4.2
Touch Screen and Overlay Material ............................
4.2.1
4.2.2
4
4
4
5
5
5
5
6
6
7
10
12
12
14
Autoflex EB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Touch Screen Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
5 Operator Panel Drawings ..............................................
5.1
Connectors .......................................................
5.2
Communication Ports ...........................................
5.3
T7F-2 Outline ...................................................
6 Additional Installation Tips ............................................
6.1
Grounding the operator panel ..................................
6.2
Ethernet Connection in the Operator Panel ...................
6.3
To Achieve Better EMC Protection .............................
6.4
Ambient Temperature ...........................................
6.5
Safety .............................................................
6.6
Galvanic Isolation ................................................
6.7
Cable and Bus Termination RS485 .............................
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16
16
17
18
18
19
21
22
23
24
25
Safety Precautions
1
Safety Precautions
Both the installer and the owner and/or operator of the operator panel must read
and understand this installation manual.
1.1
•
•
•
•
•
•
•
•
•
•
•
•
General
Read the safety precautions carefully.
Check the delivery for transportation damage. If damage is found, notify the
supplier as soon as possible.
The supplier is not responsible for modified, altered or reconstructed
equipment.
Use only parts and accessories manufactured according to specifications of
the supplier.
Read the installation and operating instructions carefully before installing,
using or repairing the operator panel.
Never allow fluids, metal filings or wiring debris to enter any openings in the
operator panel. This may cause fire or electrical shock.
Only qualified personnel may operate the operator panel.
Storing the operator panel where the temperature is lower/higher than
recommended in this manual can cause the LCD display liquid to
congeal/become isotopic.
The LCD display liquid contains a powerful irritant. In case of skin contact,
wash immediately with plenty of water. In case of eye contact, hold the eye
open, flush with plenty of water and get medical attention.
The figures in this manual serves an illustrative purpose. Because of the many
variables associated with any particular installation, the supplier cannot
assume responsibility for actual use based on the figures.
The supplier neither guarantees that the operator panel is suitable for your
particular application, nor assumes responsibility for your product design,
installation or operation.
It is recommended to turn on and shut down the operator panel at least once
before installing any components/cards or before connecting the operator
panel to external devices, like for example serial devices.
1.2
During Installation
•
The operator panel is designed for stationary installation on a planar surface,
where the following conditions are fulfilled:
–
no high explosive risks
–
no strong magnetic fields
–
no direct sunlight
–
no large, sudden temperature changes
•
Install the operator panel according to the accompanying installation
instructions.
Ground the operator panel according to the accompanying installation
instructions.
Only qualified personnel may install the operator panel.
Separate the high voltage, signal and supply cables.
•
•
•
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Safety Precautions
•
•
Make sure that the voltage and polarity of the power source is correct before
connecting the operator panel to the power outlet.
Peripheral equipment must be appropriate for the application and location.
1.3
•
•
•
Keep the operator panel clean.
Emergency stop and other safety functions may not be controlled from the
operator panel.
Do not use excessive force or sharp objects when operating the touch screen.
1.4
•
•
•
•
•
•
Service and Maintenance
Only qualified personnel should carry out repairs.
The agreed warranty applies.
Before carrying out any cleaning or maintenance operations, disconnect the
equipment from the electrical supply.
Clean the display and surrounding front cover with a soft cloth and mild
detergent.
Replacing the battery incorrectly may result in explosion. Only use batteries
recommended by the supplier. During the warranty period, the battery needs
to be replaced by an authorized Beijer Electronics service center.
1.5
•
During Use
Dismantling and Scrapping
The operator panel or parts thereof shall be recycled according to local
regulations.
The following components contain substances that might be hazardous
to health and the environment: lithium battery, electrolytic capacitor and
display.
1.6
Appearance of Air in Touch Screen
The layer structure of the touch screen contains air and in rare cases appearance of
bubbles can arise. This is purely cosmetic and does not affect any functionality
of the operator panel. The appearance can occur under certain environmental
conditions such as temperature, humidity, and atmospheric pressure.
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Installation
2
Installation
2.1
Space Requirements
•
•
Maximum installation plate thickness: 6 mm
Space requirements in millimeters when installing the operator panel:
Note:
The dimensions on the drawing are not proportional.
Caution:
The openings on the enclosure are for air convection. Do not cover these openings.
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Installation
2.2
Installation Process
1. Unpack and check the delivery. If damage is found, notify the supplier.
Note:
Place the operator panel on a stable surface during installation.
Dropping the operator panel or letting it fall may cause damage.
2. To cut a correct opening for the operator panel, use the cut out dimensions
in the outline drawing. A separate cut out drawing is available for download
from the Beijer Electronics web site. For more information, see sections
Operator Panel Drawings and Technical Data.
3. Secure the operator panel in position using all the fastening holes and the
provided brackets and screws:
0.4 ~ 0.7 Nm
1
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3
7
Installation
4. Connect the cables in the specified order, according to the drawing and steps
below.
Caution:
•
The operator panel must be brought to ambient temperature before it is started
up. If condensation forms, ensure that the operator panel is dry before connecting
it to the power outlet.
•
Ensure that the operator panel and the controller system have the same electrical
grounding (reference voltage level), otherwise errors in communication may
occur.
•
Ensure that the voltage and polarity of the power source is correct.
•
Separate high voltage cables from signal and supply cables.
•
Shielded communication cables are recommended.
B
Power
Controller
RS232/
RS422/
RS485
24V DC
24V DC
C
D
A
Ethernet
Connect cable A.
Connect cable B, using an M5 screw and a grounding conductor (as short
as possible), that is sized correctly according to local electrical codes.
–
Connect cable C.
–
Connect cable D. The recommended cross-section of the cable is
1.5 mm2.
5. Carefully remove the protective film over the operator panel display, take care
to avoid static electricity that could damage the panel.
–
–
Note:
When connecting the operator panel to the power outlet for the first time, make
sure not to interrupt power for a minimum of 48 hours in order to charge the battery
completely. After that, the battery may be charged partly during a shorter period of
time.
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Installation
2.2.1
Connections to the Controller
For information about the cables to be used when connecting the operator panel to
the controller, please refer to the help file for the driver in question.
2.2.2
Other Connections and Peripherals
Cables, peripheral equipment and accessories must be suitable for the application
and its environment. For further details or recommendations, please refer to the
supplier.
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Technical Data
3
Technical Data
Parameter
T7F-2
Front panel, W × H × D
196 × 146 × 7.5 mm
Cut out dimensions,
W×H
185.8 × 135.8 mm
Mounting depth
44.7 mm (145 mm including clearance)
Front panel seal
IP 65
Rear panel seal
IP 20
Touch screen
material
Polyester on glass, resistive.
Overlay: Autoflex EB(1).
Touch screen
operations
1 million finger touch operations
Reverse side
material
Plastic (PC+ABS)
Frame material
Plastic (PC+ABS)
Weight
0.7 kg
Serial port for
COM1 RS232 and
COM2 RS422/RS485
9-pin D-sub contact with RS232 RTS/CTS, chassis-mounted
female with standard locking screws 4-40 UNC
Serial port for
COM3 RS232 and
COM4 RS485
9-pin D-sub contact, chassis-mounted female with standard
locking screws 4-40 UNC
Ethernet
1 × 10/100 Base-T (shielded RJ45)
USB
1 × USB Host 2.0, max output current 400 mA
Processor
400 MHz ARM9
Flash memory
(application
memory)
256 MB SSD (NAND Flash)
Application memory 200 MB
Memory RAM
128 MB (DDR2)
LED
1 × blue/red software programmable
Real time clock
Yes (on chip)
Battery
Lithium ion, 3V / 200 mAh
Power consumption
at rated voltage
9.6 W
Fuse
Internal DC fuse, 2.0 AT, 5 × 20 mm
Power supply
+24 V DC (18 to 32 V DC)
(galvanic isolation).
CE: The power supply must conform with the requirements
according to IEC 60950 and IEC 61558-2-4.
Display
TFT-LCD with LED backlight
800 × 480 pixels, 64 k colors
Active area of
display, W × H
154.1 × 85.9 mm
Operating
temperature
-10 °C to +50 °C
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Technical Data
Parameter
T7F-2
Storage temperature
-20 °C to +60 °C
Relative humidity in
operation
<85% non-condensed
Approvals and
certifications
CE / FCC / KCC
Information is available on the web site
www.beijerelectronics.com
UL approval
No UL certification.
(1) See section Chemical Resistance for more information.
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Chemical Resistance
4
Chemical Resistance
4.1
Plastic Casing
The frame and casing material is plastic (PC+ABS). This material withstands
exposure to the following chemicals without visible change:
Acetic acid 10%
Nitric acid 10%
Baysilon® M 300
Phosphoric acid 30%
Citric acid 10%
Sea water
Cleaning agent, Dor®
Sodium hypochlorite
Curd soap solution 2%
Sodium thiosulphate
Hydrochloric acid 20%
Sulphuric acid 30%
Hydrogen superoxide 30%
Urea
Lactic acid 10%
-
The material shows limited resistance to the following chemicals at room
temperature:
Cleaner’s naphtha, free from aromatic
hydrocarbons
Heating oil
Ethyl alcohol 96%
Isopropanol
Glycerin
N-hexane
Glycol
Persil powder in solution
Note:
If exposure to any of the above chemicals is demanded, it is recommended to first test
the chemical in a hidden spot of the plastic casing.
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Chemical Resistance
The material shows little or no resistance to the following chemicals at room
temperature:
Acetone
Methylisobutyl ketone
Ammonia solution, diluted
Naphthalene
Aniline
Nitrobenzene
Aromatic hydrocarbons
Oleic acid
Benzene
Olive oil
Bromin
Phenol
Butter
Potassium carbonate, sat.
Chlorine
Sodium hydroxide solution 10%
Diethyl ether
Soya oil
Iodine
Toluene
Lard
Trichloroethylene
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Chemical Resistance
4.2
Touch Screen and Overlay Material
4.2.1
Autoflex EB
Autoflex EB covers the overlay surrounding the screen.
Solvent Resistance
Autoflex EB withstands exposure of more than 24 hours duration under
DIN 42 115 Part 2 to the following chemicals without visible change:
Ajax / Vim in solution
Downy / Lenor(1)
Phosphoric acid (<30%)
Alkalicarbonate
solution(1)
Ethanol
Potassium ferricyanide
Ammonia (<40%)(1)
Glycerine
Potassium hydroxide (<30%)
Acetic acid (<50%)
Glycol
Pure Turpentine
Ariel powder in
solution(1)
Gumption(1)
SBP 60/95(1)
Bleach(1)
Hydrochloric acid (<36%)
Sulfuric acid (<10%)
Castor oil
Linseed oil
Tomato ketchup
Caustic soda (<40%)(1)
Methanol
Trichloroacetic acid (<50%)
Cutting oil
Nitric acid (<10%)
White Spirit
Cyclohexanol
Paraffin oil
Windex(1)
Diacetone alcohol
Persil powder in solution(1) Wisk
Diesel
Petroleum spirit(1)
(1) Extremely faint glossing of the texture was noted.
Autoflex EB withstands DIN 42 115 Part 2 exposure of up to 1 hour duration to
glacial acetic acid without visible change.
Autoflex EB is not resistant to high pressure steam at over 100 °C or the following
chemicals:
Concentrated mineral acids
Benzyl alcohol
Concentrated caustic solution
Methylene chloride
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Chemical Resistance
4.2.2
Touch Screen Surface
The touch screen surface on the operator panel withstands exposure to the
following solvents without visible change:
Solvents
Time
Acetone
10 minutes
Isopropanol
10 minutes
Toluene
5 hours
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Operator Panel Drawings
5
Operator Panel Drawings
5.1
Connectors
COM 1/2
LAN
COM 3/4
2
3
4
1
Pos.
Connector
Description
1
Power supply
+24 V DC (18-32 V DC)
2
COM 1/2
Communication Ports
3
LAN
1 × 10/100 Base-T (shielded RJ45)
4
COM 3/4
Communication Ports
5.2
Pin
Communication Ports
Serial port, 9-pin female
COM1
COM2
RS422 Tx+
Serial port, 9-pin female
COM3
COM4
-
RS485 Tx+/Rx+
1
-
2
RS232 RxD
-
RS232 RxD
-
3
RS232 TxD
-
RS232 TxD
-
4
-
RS422 Rx+
-
-
5
GND
GND
GND
GND
6
-
-
RS485 Tx-/Rx-
7
RS232 RTS
-
-
-
8
RS232 CTS
-
-
-
9
-
RS422 Rx-
-
-
Beijer Electronics, MAEN181
RS485 Tx+/Rx+
RS422 TxRS485 Tx-/Rx-
16
Operator Panel Drawings
5.3
T7F-2 Outline
A
[mm]
22.2
B
C
D
196
E
146
7.5
Max. 6.0
44.7
5.5
35.6
135
92.8
5.5
41.1
114.8 185
A.USB Host
B. COM3 / COM4
C. Ethernet
D. COM1 / COM2
E. 24V DC
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Additional Installation Tips
6
Additional Installation Tips
When experiencing communication problems in for example noisy environments
or when operating close to temperature limits, the following recommendations
are to be noticed.
6.1
Grounding the operator panel
Mounting plate in the cabinet
Door
Operator panel
3
2
Power supply
1
Ferrite core
24 V DC
5
6
4
5350
The mounting clamps of the operator panel do not provide a secure grounding
connection between the panel and the device cabinet, see 1 in drawing above.
1. Connect a wire, that is sized correctly according to local electrical codes,
between the quick-connect terminal connector on the operator panel and the
chassis of the panel, see 2 in drawing above.
2. Connect a wire or grounding braid, that is sized correctly according to local
electrical codes, between the chassis of the operator panel and the closest
grounding point on the door, see 3 in drawing above.
3. Connect a strong but short grounding braid between the door and the device
cabinet, see 4 in drawing above.
4. Twist the cables onto the 24 V DC feed, see 5 in drawing above.
2 turns around the ferrite core provide 4 times the suppression of 1 turn.
3 turns around the ferrite core provide 9 times the suppression of 1 turn.
A ferrite core suppresses disturbances to the 24 V feed, see 6 in drawing above.
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Additional Installation Tips
Note:
The grounding wires should be short and the conductor should have a large area.
A long, thin grounding wire has a very high impedance (resistance) at high frequencies
and does not guide disturbances to the ground.
Multi-wire conductors are better than single wire conductors with the same area.
A braided conductor wire with the same area is even better. The best is a short, thick
grounding braid.
6.2
Ethernet Connection in the
Operator Panel
Industrial Ethernet
RJ45
RJ45
1
RJ45
RJ45
Operator panel
RJ45
3
2
Operator panel
RJ45
4
Shielded
1-1
2-2
3-3
Short and
unshielded
Operator panel
RJ45
8-8
5
Operator panel
RJ45
0.1 μF
250 V
In some industrial units for Ethernet, the RJ45 contact’s shield is connected to the
chassis via a capacitor, see 1 in drawing above.
The operator panel’s Ethernet shield is directly connected to the chassis, see 2 in
drawing above.
1. Check whether the other Ethernet unit has its shield directly grounded or
grounded via a capacitor.
Note:
In many cases, connecting the shielded Ethernet cabling to the chassis at both ends is
inappropriate. Hum or grounding loops can occur. Unshielded cabling may even result
in fewer communication errors.
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Additional Installation Tips
A good solution may be to use a shielded Ethernet cable, but to connect the shield
at one end only.
One option is to break the shield, see 3 in drawing above.
A more elegant method is to expand the shielded Ethernet cabling with a piece of
unshielded Ethernet cable, see 4 in drawing above.
The shield can be grounded via an external 0.1 μF/250 V plastic capacitor, see 5 in
drawing above. This connects the HF transients to ground.
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Additional Installation Tips
6.3
•
•
•
•
•
•
•
To Achieve Better EMC Protection
Use shielded cables for RS232 communication.
Use twisted pair and shielded cabling for RS422 and RS485.
Use the cabling intended for the bus type; Ethernet, Profibus, CC-Link,
CAN, Device Net etc.
Install and connect according to applicable specifications for the relevant bus
standard.
Use shielded cabling for Ethernet, preferably with foil and a braided shield.
D-sub covers should be shielded, and the shield should be connected to the
cover 360° where the cable enters.
Connect the shield at both ends.
Shielded cable
0.1 μF/250 V
Ground plane 1
Ground plane 2
Not same potential
Ground plate in another building
Ground plate
With longer distances, there is a risk that the ground potential may be different.
In that case, the shield should only be connected at one end. A good alternative
is to connect the other end of the shield to the ground via a 0.1 μF/250 V plastic
capacitor. Both ends are then connected to the ground in terms of HF, but only
connected to the ground at one end in terms of LF, thus avoiding the 50/60 Hz
grounding loops.
Metal cabinet
Metal cabinet
Terminal or connector
Short distance
Terminal or connector
EMC cable gland
Shielded cable
Cable clamp
in steel
Plastic cable gland
Shielded cable
1. Use an EMC cable gland or regular plastic cable gland, remove the outer jacket
and connect the shield to the installation plate with a 360° metal cable clamp.
2. Place the 24 V DC and communications cabling in one cable trunk/cable duct
and 230/380 V AC in another. If the cables need to be crossed, cross them at
90° only. Avoid combining the cabling for stronger 24 V DC outputs with
the communication cabling.
Ferrite cores that are snapped onto the shielded cabling may remove minor
disturbances. Large ferrite pieces that are snapped onto unshielded cabling and
where the wires go 2-4 times around the cores are approximately 5-25 times more
efficient.
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Additional Installation Tips
6.4
Ambient Temperature
The maximum ambient temperature for the operator panel is provided in the
specifications. The ambient temperature refers to the temperature in the device
cabinet which cools the operator panel’s electronics.
Top
50 °C inside
Operator
panel
Power
Power
30 °C outside
Middle
45 °C inside
Axial fan
120 x 120 mm
Airflow
Power
Bottom
40 °C inside
In most cases, the ambient temperature for the operator panel is significantly
higher than the device cabinet’s ambient temperature.
If the cabinet is tall and there are a number of heat-generating devices, the
temperature at the top of the cabinet is considerably higher than the temperature
increase that would be expected. All electronics are sensitive to heat. The lifespan
of an electrolytic capacitor is cut in half with an 8-10 °C increase in temperature. A
15-20 °C temperature increase results in a quarter of the lifespan etc.
Rittal has a good program for estimating the anticipated average temperature in
the cabinet as well as a large program for controlling the temperature in the device
cabinet.
An enamel-coated steel cabinet has a radiant heat value of 5.5 W/m2 and degrees
C.
Installing a fan inside the cabinet evens out the temperature, while moving air
provides considerably better cooling than still air. A suitable fan is a 120 x 120 mm
axial fan, available in 24 V DC, 115 V AC and 230 V AC.
Install the fan so that it sits in a cooler area and blows cold air against the operator
panel. If the fan is mounted at the top and sucks warm air upwards, the ambient
temperature of the fan becomes higher, resulting in a shorter lifespan.
A good fan with a ball-bearing mounting has an expected lifespan of at least
40,000 hours (not a guaranteed lifespan) at 40 °C. This corresponds to at least 4
years of continuous use. If a thermostat is installed, the fan only operates when
needed.
Large graphic terminals draw only one fifth of the current when the background
lighting is off. The loss effect drops from e.g. 25 W to only 5 W.
An approximate value of the net power consumption for the operator panel can
be calculated by multiplying the supply voltage with the current drawn by the
operator panel. This is assuming that all supplied power is transformed to heat.
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Additional Installation Tips
6.5
Safety
Most of the operator panels are fed with 24 V DC.
Power supply
230 V AC to 24 V DC
Operator panel
+24 V
1
0V
4
Power supply
230 V AC to 24 V DC
Operator panel
+24 V
2
0V
4
Distance?
Power supply
230 V AC to 24 V DC
Operator panel
+24 V
3
0V
4
COM1
Small controller with expansion unit
Ch0
Ch1
230 V AC
COM100
Ch100
Ch101
5355
If a power supply that meets safety standards is used and only feeds the operator
panel, there is no problem. See 1 in drawing above.
However, if a 24 V unit that also feeds other units is used, there is reason to be
cautious, see 2 in drawing above. The operator panel does not have insulation
that meets safety requirements in the event of a potential short circuit between
230 V AC and 24 V DC. It is assumed that the 24 V feed is secure, for example,
SELV according to EN 60950 (protection against electric shock) and UL 950.
Note:
Here is an example that explains why a secure 24 V DC feed can be ruined by mixing
24 V relay contacts with 230 V AC relay contacts in a smaller controller. Check that the
clearances and creepage distances between 24 V DC and 230 V AC fulfill EN 60950 or
UL 950. If not, input a separate 24 V unit into the operator panel.
If there is a substantial distance between the relay contacts for 24 V DC and
230 V AC, it is OK to use the same 24 V devices for all feeds. See 3 in drawing
above.
Connect 0 V on the 24 V feed to the ground, see 4 in drawing above. This offers
three advantages:
•
Safety is increased. The 24 V feed is not live in the event of a faulty connection
or short circuit between 0 V (24 V) and 230 V phase.
•
Transients on the 24 V feed are connected to the ground.
•
No risk that the 24 V feed is at a high level in relationship to the ground. This
is not unusual since there is high static electricity.
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Additional Installation Tips
6.6
Galvanic Isolation
Internal electronics
Ethernet
DC/DC
galvanic isolation
Filter
DC/AC
VCC
+24 V DC
CFL
0 V (GND)
0V
1.5 m
RS422/485
RS232
USB
USB
The operator panel has galvanic isolation against the 24 V DC feed but no galvanic
isolation between the communication ports for RS232, RS422/485 and USB.
Only the Ethernet connection has galvanic isolation.
Operator panel
Modular controller
Power CPU
RS422
*
RS232
PC
*
*
Printer
COM COM2
*
* * *
USB
*
PC
Different ground potential
*
*
= Internal 0 V (GND) connection
When a PC is connected to the operator panel, the internal 0 V (GND) of the
panel is connected to the protective ground via the PC.
A number of USB devices can have the shield connected together with the
protective ground. Here, the 0 V (GND) of the operator panel is connected to the
protective ground when, for example, a USB memory stick, keyboard, or similar
device is plugged in.
If a number of units are connected that have a 0 V and a ground connection, and
these are connected to various grounding points, there is a substantial risk of
problems. Grounding currents go through communication cables, the rear plate
of the controller, and internally in the operator panel, and can cause errors.
Use external units to improve communication and achieve galvanic isolation.
Westermo has good industry-standard insulators that are also insulated from the
24 V DC feed.
Note:
It is very important to make sure that the 24 V feed in the external insulation unit is not
connected to one of the communication outlets. If it does not have 100% insulation
against the 24 V feed, disturbances and grounding currents from the 0 V on the 24 V
side disrupts the communication.
Using this type of unit solves one problem but creates a larger problem! A substandard
installation may work now, but problems may arise when other devices are connected.
Beijer Electronics, MAEN181
24
Additional Installation Tips
6.7
•
•
•
Cable and Bus Termination RS485
If maximum transfer distance and maximum transfer speed is needed,
shielded and twisted pair cable should be used. The mutual capacitance
may not exceed 52.5 pF/m, and the cable area should be at least 0.25 mm2
(AWG 24).
0 V, the reference voltage for communication should be included in
the cabling. With two-way communication use two pairs; one pair for
communication and one pair for 0 V.
The shield must be grounded at one end. The other end is usually grounded,
but with longer distances or when there is a difference in the ground potential,
the shield should be connected to the ground via 0.1 μF/250 V plastic
capacitor to prevent ground current in the braided shield. A number of
manufacturers recommend that the shield be grounded at each node. Various
manufacturers have different systems for bus termination. The RS485
standard does not describe how the “Fail Safe” function would be carried out,
just that the system should be able to handle the error.
Depending on the recipients’ design, the bus wires may be on the same level or
require pull-up or pull-down to ensure that no faulty signals are detected when the
bus is in resting mode (all transmitters are disconnected).
Beijer Electronics, MAEN181
25
Head office
Beijer Electronics AB
Box 426
201 24 Malmö, Sweden
www.beijerelectronics.com / +46 40 358600

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