DREHMO EX-proof Actuators – Interfaces
Analog/digital I/O
The connection of the i-matic by means of analogue and digital inputs and outputs takes place via the relay interface.
The various assemblies, which are equipped differently depending on the variant, are operated directly by the central microcontroller (µC).
The command inputs and signal outputs are not only insulated against electrical potential, but are also bundled together to form smaller groups.
The functions of the six command inputs and up to a maximum of eleven signal outputs can be allocated to the available channels as you wish. With the command inputs it is also possible to set the active level as "voltage present" (high active) or as "voltage not present" (low active).
The physically available normally open contacts of the signal outputs can be configured via the software as normally open or normally closed contacts - signal output Out 7 consists of a single-throw contact.
Profibus DP (V1 / V2) single channel / redundant
The connection of the i-matic by means of a profibus channel takes place via the "single-channel profibus" interface board.
The ASIC that controls the profibus communication is connected directly to the central microcontroller (µC). The central µC supplies the ASIC with the required data, such as the bus address. The bus address can be set anywhere between 2...126 using the software. The transfer of the data to the profibus takes place via an electrically isolated RS-485 interface.
The line redundant board is based on the single-channel board, but is extended by a second channel and an automatic selection logic. The actuator can be equipped with four digital inputs for 24 V DC and two analogue inputs for 4...20 mA.
The conditions of these additional inputs are sent to the master station via the profibus protocol. In case of slave redundancy each profibus channel has its own ASIC, which is connected directly to the central µC. The central µC supplies the ASICs with the required data, such as the bus addresses, which can be set to different values anywhere between 2...126 for both channels.
This means that independent communication is possible with 2 masters that send simultaneously. There is also the option of implementing the acyclic services of the DPV1 profibus to enable parameterization of the device and read-out of the memory for data acquisition, diagnosis information an documentation data via the fieldbus.
DPV2 functions such as clock synchronisation and time stamps for events are integrated in the V2 Profibus extension.
Profibus DP slave-redundant interface
Profibus with optical fibres
For plant installations with long cables and with high risks of EMC or lightning strike, profibus interfacing does not take place via two-wire copper cables; instead, the participants are connected via optical fibres. For this purpose, a converter from copper RS485 technology to light signals (optical fibre coupler) is used both on the master and on the field devices. The following wiring concepts are supported in the i-matic series:
Star topology of the actuators on the profibus
Star topology
Each actuator has a transmitter and receiver cable that connects it to the inverse coupler on the master.
Line topology of the actuators on the profibus
Line topology
The transmitter and receiver cables are connected through via the optical fibre couplers in the actuators. Unlike the line structure in copper technology with T-connectors, the failure of a participant in this optical fibre technology interrupts the line. None of the participants further down the line can be reached.
Ring topology of the actuators on the profibus
Ring topology
The transmitter and receiver lines are connected through via the optical fibre couplers of the devices and there is a pair of feedback lines to the master, forming an optical fibre ring. Even if one of the participants fails or there is a line break, the rest of the participants can still be reached, as transmitting and receiving is possible in both directions.
Modbus RTU interface
The actuator can be controlled by Modbus RTU technology with an appropriate optional PCB-board. Two independent 2-wire RS485 channels are available on this board, each of them electrically isolated from the attached control logic. A dual channel UART connects the physical interface with the central microcontroller.
The Modbus RTU communication protocol allows bitwise - single and multiple - and wordwise access to the linear mapped actuator input and output data by means of various function codes. If the actuator is equipped with the optional process inputs (digital and analogue), these values are available in the accessible actuator data mapping.
