In the MODBUS network any MODBUS Master can be connected to one or several LINAK LA35/LA36 Actuators with MODBUS interface. The topology is a serial bus-system with actuators including derivation cable connected to a trunk cable through passive TAPs.
Passive TAPs Terminator Trunk cable Derivation cable/Stub LINAK Actuators Modbus RTU slaves Safety instructions Be aware of the following symbols throughout the installation guide: Recommendations Failing to follow these instructions can result in the actuator suffering damage or being ruined.
Installation Connection, cables and plugs The actuator data and power cables are separate from each other and pre-mounted on the LA35/LA36/LA37 Actuators. Power cable Standard LA35, LA36 and LA37 power cables are used. The power cable is an open-end flying leads version. The following issues must be considered when extending the power cable: There are no specific requirements for the power cable itself other than it of course needs to be dimensioned to handle the maximum voltage drop for the actuator with the longest cable distance from the power supply.
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RS485 transceiver manufacturers specify the opposite, which is a widespread misunderstanding. As LINAK only supplies the derivation cabling from actuator to the nearest TAP in the trunk, the longer distance cabling that interconnects the individual TAPs is the responsibility of the customer/system integrator.
The termination is made with a 120 Ohms (0.25 W) resistor (see figure below). Line biasing No line biasing is necessary for the LINAK MODBUS actuators to function, as their isolated RS485-transceivers are true fail-safe, meaning that they correctly handle an idle bus (no enabled driver on the bus).
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• The quality of the cabling • The functionality i.e. the poll rate Based on our tests, a bus string with a master, 32 LINAK actuators and no 3’rd party slaves will work under the following conditions: • Baud rate: Up to 19200 •...
Reverse polarity protection In the case of reversing the polarity of the power to the actuator, a protection diode gets into action (short cir- cuiting the input voltage). The result is a very high current. As the protection diode has a limited current handling capability, the fuse mentioned above must open in order to limit the duration of the short circuit.
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Example 2 The selected power supply has a current limit of 100A. The selected fuse protecting each actuator has a nominal rating of 10A and a guaranteed opening time at 1000% rated of maximum 150ms. If the actuator is connected with reverse polarity, the fuse (and the reverse polarity diode in the actuator) will see 100A of current.
Modbus RTU Functional Description Implementation class The LINAK MODBUS protocol is implemented conforming to the “basic slave” implementation class as described in document [1]. The following options have been implemented: Parameter Options Default value Remarks Adressing Configurable from 1 to...
Unicast/broadcast MODBUS is a single master system, which means that only one master can be connected at any single point in time. Two modes of communication are possible, Unicast and Broadcast. Request/response (unicast) The requests from the master are addressed to a given slave. The master then waits for the response from the slave which has been interrogated.
Parity checking A LINAK MODBUS device can be configured for even or odd parity, or for no parity checking. This determines how the parity bit of the character’s data frame is set. If even or odd parity checking is selected, the number of 1 bits in the data portion of each character frame is counted.
Register-parameter mapping All data addresses in MODBUS messages to LINAK actuators are referenced to zero. The input register known as e.g. ‘Input Register 30002’ in a programmable controller is addressed as register 1 in the Addr field of a MODBUS message.
Registers. Different datatypes are mapped into theses addressable registers. The type of any parameter value embedded into the MODBUS message has to be recognised according to the register/parameter tables in Appen- dix A. LINAK MODBUS devices support the following datatypes (illustrated by single register write-message examples): Short integer register (U8) Status bytes and small integer values are stored in MODBUS registers where only half of the register is utilised.
U32- Function codes The LINAK actuator supports a subset of the standard MODBUS RTU function codes to provide access to the internal actuator parameters and functions. The LINAK MODBUS protocol does not support the Diagnostic function (function code 08). As a more general approach, the MODBUS master –...
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Function code 4 – Read Input Registers Function code 4 is used to read one or more input registers in the actuator, referenced in Appendix A. When the master accesses a register that is not supported by the slave, it responds with an exception message. The register address in this context is without ‘3xxxx’...
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The normal response is an echo of the request message. Response message: Addr Function Register address Register data Slave Function Address Address New Value New Value Address Code (=6) High High Function code 16 – Write Multiple Holding Registers Function code 16 is used to write one or more holding registers in the actuator, referenced in Appendix A. When the master accesses a register that is not supported by the slave it responds with an exception message.
Exceptions When a MODBUS master transmits a request to a slave the expected behaviour is that the slave responds with a normal response. But several error scenarios are possible: • The slave does not receive the request due to a communication error. No response is returned; the master will process a time-out and eventually repeat the request.
Typical Use Cases In this section further descriptions of how to communicate with the LINAK LA35/LA36/LA37 Actuators are shown. The examples are typical user scenarios and application solutions. All examples include references to registers, which are further described in details in Appendix A.
When the actuator wakes up after power down and sees that the state of the two hall sensors has changed, the “position valid” bit will be set to “0”. On firmware versions 1.2 and lower, it is required to do an initialisation run in either inwards or outwards direction. On firmware versions 1.3 and higher, it is NOT required to do an initialisation run, but it is recommended, to be sure that the position is valid.
In some large MODBUS communication systems the sequential and time-consuming polling of the slaves by the master makes it hard to command multiple actuators to move at the same time. The LINAK LA35/LA36/LA37 MODBUS actuator offers a feature to improve this functionality. Below is shown the process to start 3 actuators.
*IR = Input Register, HR = Holding Register Customisation of MODBUS register mapping To optimise efficiency of the MODBUS communication between a master and the LINAK LA35/LA36/LA37 Actuator(s) the device offers an opportunity to re-arrange the numbering of Input – and Holding Registers.
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Step Register * Action HR 1001 Specify input register 74, which you want to re-map by writing the number 74 to holding register 1001. If you now read holding register 1002 it will show the existing mapping to parameter 29. HR 1002 Specify the new mapping of input register 74 by writing the number 4 into holding register 1002 - as new reference to parameter 4 ‘Run Status’...
The cables can be ordered in one package with Axapta item number 0367998. When changing the cables on a LINAK actuator, it is important that this is done carefully. In order to protect the plugs and pins, please be sure that the plug is in the right location and fully pressed in before the cable lid is mounted.
• “Select Usb2Lin” can be used if you e.g. have several Usb2Lin cables connected to your PC. • In the status area in the bottom of the screen you can se the actual connection status. If an actuator is connected you can additionally se the firmware version of the actuator, the actual run-status, clock value and position.
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In the “Modbus configuration” section of the screen you can set up the communication parameters of the actuator. • ”Address” is from the factory set to 247. Remember that each unit must have its own unique address. Do not use 247 or 0 as an address. It is possible to avoid upload/download of the address value by unchecking the “Include Address”...
Screen nr. 3: ”Manual run” This tab is used to set the basic movement parameters of the actuator. • “Run Out”/”Run In” will start the actuator in the selected direction and it will run until it is either stopped or until it reaches an end-stop. •...
Screen nr. 4: ”Firmware” On this tab it is possible to install firmware into the actuator, if a new firmware version is released. • All you need to do is to select the new firmware file and press “Download.” • ....“Verify” means that you can verify the previously downloaded firmware. Verification is a time- consuming process and is normally not needed after a successful download.
Screen nr. 5: ”Service counters” The service counter tab is divided into 4 areas: • Start/Stop data where it is possible to see the total running time, number of actuator starts and stops and the reasons. • Temperatures, here it is possible to read the relevant temperatures measured on the FET transistors and the processor.
Troubleshooting Integration of a LINAK LA35/LA36/LA37 Actuator into a MODBUS system is fairly simple. But sometimes you may potentially encounter unexpected results or strange behaviour. In the following section you will find some potential problems, diagnosis suggestions, possible causes and corresponding solutions.
Problem: BusLink PC tool can not communicate with the actuator Diagnosis: Errors announced during startup or no connection to actuator. Causes/solutions: Cause: .ini file (C:\Program Files\Linak\BusLink\parametertable_0.xxx.ini) is incompatible with the actuator. Solution: Update .ini file to match the current actuator parameter table version.
Problem: Actuator firmware is corrupted e.g. due to upgrade problem Diagnosis: After firmware upgrade any digital communication with actuator is impossible. Causes/solutions: Cause: Firmware is corrupted. Solution: To activate the actuator bootloader and download new firmware using BusLink. This is done by strictly following the following procedure: •...
DECLARATION OF INCORPORATION OF PARTLY COMPLETED MACHINERY LINAK A/S Smedevænget 8 DK - 6430 Nordborg Herewith declares that LINAK TECHLINE ® products as characterized by the following models and types: Linear Actuators LA12, LA14, LA22, LA23, LA25, LA30, LA35, LA36, LA37...
Appendix A - Register Map All accessible Input- and Holding registers are listed below. Notice that the unit of the parameter values is found in column Remark’. Read Only Registers (Input Parameter list version Registers) Address Term Para- Remark Type Min.
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Read Only Registers (Input Parameter list version Registers) Address Term Para- Remark Type Min. Max. limit High/ meter limit Order EOS Out Position Pulses relative to EOS In. Set during production 65000 Actual Position (Pulses) Pulses relative to EOS In switch -1000 32000 For development/production purposes...
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Read Only Registers (Input Parameter list version Registers) Address Term Para- Remark Type Min. Max. limit High/ meter limit Order Number of Telegrams Service counter (invalid function code, invalid data etc.) 4294967295 (15:0) With Invalid Content used for debugging on system level. Also available via the BusLink service tool Number of Telegrams Service counter (total of corrupted telegrams) used...
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Read Only Registers (Input Parameter list version Registers) Address Term Para- Remark Type Min. Max. limit High/ meter limit Order For development/production purposes 65535 For development/production purposes 65535 For development/production purposes 65535 For development/production purposes 65535 For development/production purposes 65535 For development/production purposes 4095 For development/production purposes...
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Internal registers (Holding Parameter list version registers) Address Term Para- Remark Type Min. Max. limit High/ meter limit Order Target Position Resolution in 1/10mm relative to Offset 65000 Command, Remote 0 = No Command 1 = Run to target position 2 = Stop 3 = Run at “Next time to run”...
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Internal registers (Holding Parameter list version registers) Address Term Para- Remark Type Min. Max. limit High/ meter limit Order 1001 Modbus User Map Input Hardcoded to Modbus Holding register 1001 Register Address Used to set the target cell for the Parameter Address set by Modbus User Map Parameter Reference (I).
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