Wiring the S7-400
5.6 Bus Connectors
Purpose of the Bus Connector
The bus connector is used to connect the PROFIBUS-DP bus cable to the MPI or PROFIBUS-DP interface. In this way, you establish the connection to other nodes.
There are two different bus connectors:
Bus connector without PG connector (6ES7 972-0BA20-0XA0)
Bus connector with PG connector (6ES7 972-0BB20-0XA0)
Appearance (6ES7 972-0B.20 ...)
Screws for mounting on station
PG connector (only with 6ES7 972-0BB20-0XA0)
9-pin sub. D male connector for connection to MPI or PROFIBUS-DP interface
Housing screw Switch for terminating
resistor
Clamp hinge for vertical or 30° cable routing
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Connecting Bus Cables to Bus Connectors (6ES7 972-0B.20 ...) 1. Strip the bus cable according to the following figure.
5.5
Angled outgoing cable unit
Without PG connector
2. Open the housing of the bus connector by slackening the housing screw and swinging the cover upwards.
3. Slacken the clamp hinge cover.
4. The bus connector with order number 6ES7 972-0B.20 is supplied with an angled outgoing cable unit and used as it is in the S7-400.
If the cable is to be routed vertically out of the housing:
– Slacken the left-hand screw on the clamp hinge, – Raise the clamp hinge slightly, and
– Turn the clamp hinge inward.
– Screw the left-hand screw tight again.
5. Insert the green and red cores in the screw terminal block as shown in the following figure.
Ensure that the same cores are always connected to the same terminals A or B (for example, green conductor always wired to terminal A, and red conductor to terminal B).
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Bus cable connection for first and last station on the bus
Bus cable connection for all other stations on the bus
A B A B
ÇÇ
A B A B
The bus cable can be connected either right or left.
6. Retighten the clamp hinge cover.
Ensure that the bare cable shield is under the shield clamp.
7. Tighten the screw terminals for the green and red cores.
8. Close the cover of the bus connector.
9. Screw the housing on.
Connecting the Bus Connector
To connect the bus connector, proceed as follows:
1. Plug the bus connector into the module.
2. Screw the bus connector into the module.
3. If the bus connector, order no. 6ES7 972-0B.20-0XA0, is situated at the beginning or end of a segment, you must switch on the terminating resistor.
Terminating
Ensure that power is always applied to the stations at which the terminating resistor is situated, during startup and operation.
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Removing the Bus Connector
With a looped-through bus cable you can remove the bus connector from the PROFIBUS-DP interface at any time, without interrupting data traffic on the bus.
!
WarningInterference to the data traffic on the bus is possible.A bus segment must always be terminated with the terminating resistor at both ends. This is not the case, for example, when the last slave with bus connector is not under power. Since the bus connector is powered by the station, the
terminating resistor has no effect.
Ensure that the stations at which the terminating resistor is switched on are always under power.
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5.7 RS 485 Repeater
Purpose of the RS 485 Repeater
The RS 485 repeater enhances data signals on bus cables and links bus segments.
You need an RS 485 repeater when:
More than 32 nodes are connected in the network,
A grounded segment is to be connected to an ungrounded segment, or The maximum cable length of a segment is exceeded.
Description of the RS 485 Repeater
A detailed description and technical data of the RS 485 repeater can be found in the Reference Manual, Chapter 10.
Assembly
You can install the RS 485 repeater on a 35 mm standard profile rail.
Wiring the Power Supply Unit
To wire the power supply unit of the RS 485 repeater, proceed as follows:
1. Slacken the screw for “M” and “PE”.
2. Strip the cable for the 24 VDC supply.
3. Connect the cable to terminals “L+” and “M” or “PE”.
Terminal “M5.2”
Terminal “M5.2” should not be wired because it is only needed during maintenance.
Terminal “M5.2” is the reference ground you require when measuring the voltage between terminals “A1” and “B1”.
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Connecting the PROFIBUS-DP Bus Cable
Connect the PROFIBUS-DP bus cable to the RS 485 repeater as follows:
1. Cut the PROFIBUS-DP bus cable to the required length.
2. Strip the PROFIBUS-DP bus cable according to the following figure.
The braided shield must be turned back over the cable. This is essential so that the shielding point can serve later for strain relief and as a securing element.
6XV1 830-0AH10 6XV1 830-3BH10
ÇÇÇ
ÇÇÇ
ÇÇÇ
8.5 16 10
6XV1 830-3AH10
ÇÇÇ
ÇÇÇ
ÇÇÇ
8.5
16 10
16
Braided shield must be turned back over cable
3. Connect the PROFIBUS-DP bus cable to the RS 485 repeater:
Connect the same cores (green/red for PROFIBUS-DP bus cable) to the same terminal A or B (for example, green conductor always connected to terminal A and red conductor to terminal B).
4. Tighten the shield clamps so that the bare shield makes contact under the shield clamp.
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