2 MODBUS Coupler/Controller
2.1 Hardware
Fig. 2.1: MODBUS coupler/controller
The illustration above applies both to the MODBUS coupler as well as for the MODBUS controller.
Each coupler/controller comprises of two enclosure sections:
left: |
enclosure for the electronics for bus connection and processing |
right: |
a fixed installed power supply module as connection and distribution for the |
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power supply to the electronics in the coupler/controller enclosure, the |
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assembled I/O modules and the power supply in the field area. |
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2.2 Power supply
Fig. 2.2: Power supply
The power supply on the field side is electrically isolated from the electronic supply. In this manner sensors and actuators can be supplied and fused by a separate voltage source.
If a non-regulated power supply is used for the 24 V voltage supply of the coupler/controller electronics, it must be ensured that they are supported by a capacitor (200 µF per 1 A load current). To this effect a back-up capacitor module 1 was developed for the WAGO-I/O SYSTEM. This module serves for smoothing an unstable 24 V DC voltage supply, in as much as the specified voltage deviation required cannot be maintained. Cause for these fluctuations could be a voltage interruption on the primary side, a secondary side overload or the switching of “non quenched” inductivity and capacities.
ATTENTION!
Under no circumstances connect a voltage supply other than 24 V DC on the + and – power supply modules of the coupler/controller. A power supply voltage of max. 230 V AC can only be supplied via the power supply modules 750-609, 750-611 and 750-612!
ATTENTION!
Disconnect the PE lead wires prior to undertaking an insulation test, otherwise this will result in incorrect results or destruction of the I/O module.
1 Back-up capacitor module, Order No. 288-824 |
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2.2.1 Electronic supply voltage
Fig. 2.3: Electronic supply voltage
The electronic supply voltage (24 V DC) is adapted using a voltage regulator and led to the coupler/controller electronics as well as to the internal bus. The electrical isolation of the external fieldbus system is made via a DC/DC converter and via an optocoupler in the fieldbus interface.
The internal bus includes the internal communication between the coupler/controller and the I/O modules as well as the power supply for the I/O modules. The maximum power supply is 1.65 A. If the sum of the internal power consumption of all I/O modules exceeds this value it is necessary to fit additional internal system supply modules2.
The control electronics in the I/O modules are supplied by snap-fit mounting the I/O modules using the internal bus contacts. A reliable contact is assured by gold plated, self cleaning slide contacts. The removal of a I/O module will cause an interruption of the connection to the following I/O modules. The coupler/controller localises the interruption point and sends a corresponding fault message via the red LED ‘I/O ERR’.
ATTENTION!
Removing or inserting the I/O modules with the voltage applied can lead to undefined conditions. For this reason only undertake work on the I/O modules when isolated from the power supply!
2 Internal system supply modules, order No. 750-613
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2.2.2 Supply voltage of the field side
Fig. 2.4: Power contact for the power supply to the field side
The power is supplied to the field side automatically by snap-fitting the individual I/O modules via self-cleaning power contacts (Fig. 2.4). These contacts are arranged on the right hand side of the coupler/controller and the I/O modules, protected against accidental contact, as spring contacts. On the left hand side of the I/O modules are corresponding male contacts as counter pieces. Ensure that the current of the power contacts does not permanently exceed 10 A.
The PE contact is a preceding ground (earth) contact corresponding to the standards which can be used as a protective earth. The contact has a leakage capacity of 125 A.
яюэьыъщэш Please note that some I/O modules do not have any, or only individual power contacts (dependent of the I/O function). This configuration is intended to interrupt the power supply. If a field supply is required for the following I/O modules, it is necessary to use a power supply module. Take note of the individual terminal/module data sheets! The design of some modules does not physically allow assembly them in rows as the grooves for the male contacts are closed at the top.
By fitting an additional power supply module the field supply is always interrupted by the power contacts. From this point a new power supply is made, which can also include a potential change (see Fig. 2.2). This possibility guarantees a high degree of system flexibility.
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