BRASCH SG01 Modbus Client Server Communication Installation Guide
- September 18, 2024
- BRASCH
Table of Contents
**BRASCH SG01 Mod bus Client Server Communication Installation Guide
**
Operation Safety Notice
Certain procedures and operations detailed in this guide require that specific precautions be taken prior to beginning the procedure or operation. When precautions are required, a notice will be printed in an appropriate location in the guide. The user is urged to read and understand all such notices.
Types of Notices
Three types of notices may be used in this guide to describe the severity
of the situation encountered.
WARNING: This notice indicates that conditions exist that could cause personal injury or loss of life.
CAUTION: Conditions exist that could cause damage to the equipment or other property.
Note: Special consideration should be given to the procedure or operation, otherwise an unexpected operational result could occur.
Introduction
General Description
Modbus is a messaging structure for establishing client-server communication
between smart devices. It is an open standard and the most widely used network
protocol in the industrial manufacturing environment. Modbus is used to
monitor and program devices, communicate between sensors and instruments, and
monitor field devices using PCs and HMIs.
Brasch sensor and relay boards communicate across a two-wire RS-485 bus using
the Modbus RTU protocol. The data on this bus can be read by a remote device
capable of interfacing with this protocol. In this configuration, the remote
device is the client and the sensor or relay board is the server.
This document will serve as a reference for technical information pertaining
to the installation and setup of the Brasch boards when used in a larger
Modbus system. The following documents should also be used during this
process:
-
Brasch Gen 2 Remote Transmitter IOM:
https://braschenvtech.com/wp-content/uploads/XXXXXXX -
Brasch GDCP-Touch IOM:
https://braschenvtech.com/wp-content/uploads/2021/05/GDCP-Touch-IOM.pdf -
Modbus Manual: https://modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf
Use the following information to configure remote devices to communicate with a sensor or relay board.
Features
- Communicates using Modbus RTU
- Addressable with up to 128 unique sensor addresses and 16 unique relay addresses
- Supports Function Codes (FC) 04 and 16
- Provides gas sensor readings, error codes, relay control, and analog output overrides
Note :
Modbus does not have a defined standard for communication with gas
detection systems.
As a result, the configuration is proprietary. Only the commands and registers
listed in this document are available. Any unlisted commands and registers are
assumed to be unused.
Installation
Wiring
The Brasch sensor board has one terminal block in the center of the circuit
board. The leftmost terminal is +COMM; the connection point immediately to the
right is -COMM. Refer to figure 1 on page 6 for details. The Brasch relay
board has three terminal blocks for communication, two on the bottom left and
one on the top right of the circuit board. Refer to figures 2 and 3 on pages 6
and 7 for details. Consider +COMM to be Data A and -COMM to be Data B when
wiring to the terminals. Use a shielded twisted pair cable with color-coded
wires to easily differentiate between the two terminals on each device. Brasch
recommends the Belden 3105A (22 AWG) cable, but any similar shielded data
communication cable will suffice.
CAUTION
Reversing the wiring connections to the Data A and B terminals of a device
will prevent it from communicating and may interfere with the entire system as
a result of the polarization.
If this happens, swap the device’s connections and retest the system.
Wire each device in a daisy chain configuration. The total distance should be no longer than 4000 feet. No more than 32 devices may be connected to a single bus, including the master/client/host. If more devices, or devices farther away than 4000 feet, need to be connected, repeaters may be used.
In order to avoid signal reflections, a 120 Ω termination resistor should be fitted/enabled at the master/client/host and at the farthest transmitter.
A bus configuration with branches connected to the main cable may also be used. However, there may be more limitations as the number of devices increases. The main cable should be no longer than 4000 feet with branches no longer than 3 feet. The combined length of all branches should not exceed 30 feet. Each main cable can have no more than 32 devices connected to it, including the master/client/host. As with the daisy chain, repeaters may be used to connect more devices or to increase the distance.
In order to avoid signal reflections, a 120 Ω termination resistor may be fitted on each end of the main cable. **
Figure 1 :** Sensor Board Communication Wiring
Isolated COMM (TS7)
Figure 2 : Relay Board Communication Wiring – Input
Non-isolated COMM (TS8 & TS11)
Figure 3 : Relay Board Communication Wiring – Output
Setup
Master/Client/Host Setup
Before starting, please refer to the documentation included with the
master/client/host device.
It will contain the details of its communication along with instructions for
Mod bus configuration.
Brasch recommends that the master/client/host be configured to attempt at least two retries in the event of a communication frame loss with a minimum delay of one second between each poll and a minimum timeout of two seconds.
Use the information in figure 4 below to configure the master/client/host device.
| Baud Rate | 9600 |
|---|---|
| Data | 8 bits |
| Stop | 1 bit |
| Parity | None |
| Flow Control | None |
Figure 4 : Master/Client/Host Setup Parameters
Sensor Board Setup
Each sensor board has a 7-position DIP switch (SW1) used to set the device
address.
Available addresses are 1 through 128. The address is the value of the DIP
switches plus one.
Brasch sensor boards are programmed and configured at the factory so that it
should not be necessary to alter addresses in the field. Each unit will
indicate the address assigned at the factory on its front cover label.
However, these addresses can be modified by using the DIP switch on the top,
right side of the circuit board. The address is assigned using a binary
counting system where digit 0 is towards the top of the board and 1 is towards
the bottom. Refer to figure 5 below for details.
-
Sensor
-
Sensor
-
Sensor
-
Sensor
Figure 5 : Sensor Board Addressing (1 through 4)
For a complete list of switch positions and addresses, see figure 6.
Sensor Address| Switch Position| Sensor Address| Switch
Position| Sensor Address| Switch Position| Sensor Address|
Switch Position
---|---|---|---|---|---|---|---
1| 0000000| 33| 0100000| 65| 1000000| 97| 1100000
2| 0000001| 34| 0100001| 66| 1000001| 98| 1100001
3| 0000010| 35| 0100010| 67| 1000010| 99| 1100010
4| 0000011| 36| 0100011| 68| 1000011| 100| 1100011
5| 0000100| 37| 0100100| 69| 1000100| 101| 1100100
6| 0000101| 38| 0100101| 70| 1000101| 102| 1100101
7| 0000110| 39| 0100110| 71| 1000110| 103| 1100110
8| 0000111| 40| 0100111| 72| 1000111| 104| 1100111
9| 0001000| 41| 0101000| 73| 1001000| 105| 1101000
10| 0001001| 42| 0101001| 74| 1001001| 106| 1101001
11| 0001010| 43| 0101010| 75| 1001010| 107| 1101010
12| 0001011| 44| 0101011| 76| 1001011| 108| 1101011
13| 0001100| 45| 0101100| 77| 1001100| 109| 1101100
14| 0001101| 46| 0101101| 78| 1001101| 110| 1101101
15| 0001110| 47| 0101110| 79| 1001110| 111| 1101110
16| 0001111| 48| 0101111| 80| 1001111| 112| 1101111
17| 0010000| 49| 0110000| 81| 1010000| 113| 1110000
18| 0010001| 50| 0110001| 82| 1010001| 114| 1110001
19| 0010010| 51| 0110010| 83| 1010010| 115| 1110010
20| 0010011| 52| 0110011| 84| 1010011| 116| 1110011
21| 0010100| 53| 0110100| 85| 1010100| 117| 1110100
22| 0010101| 54| 0110101| 86| 1010101| 118| 1110101
23| 0010110| 55| 0110110| 87| 1010110| 119| 1110110
24| 0010111| 56| 0110111| 88| 1010111| 120| 1110111
25| 0011000| 57| 0111000| 89| 1011000| 121| 1111000
26| 0011001| 58| 0111001| 90| 1011001| 122| 1111001
27| 0011010| 59| 0111010| 91| 1011010| 123| 1111010
28| 0011011| 60| 0111011| 92| 1011011| 124| 1111011
29| 0011100| 61| 0111100| 93| 1011100| 125| 1111100
30| 0011101| 62| 0111101| 94| 1011101| 126| 1111101
31| 0011110| 63| 0111110| 95| 1011110| 127| 1111110
32| 0011111| 64| 0111111| 96| 1011111| 128| 1111111
Figure 6: Sensor Board Addresses and Switch Positions
Relay Board Setup
Each relay board has a 4-position DIP switch (SW1) used to set the device
address. Available addresses are 129 through 144. The address is the value of
the DIP switches plus 129.
Brasch relay boards are programmed and configured at the factory so that it should not be necessary to alter addresses in the field. Each unit will indicate the address assigned at the factory on the right side label. However, these addresses can be modified by using the DIP switch near the middle of the circuit board. The address is assigned using a binary counting system where digit 0 is towards the right of the board and 1 is towards the left. Figure 7 below shows addressing for the first 8 relay boards. Refer to figure 6 above for additional boards.
Relay Board #
Figure 7: Relay Board Addressing (1 through 8)
Modbus Register Allocation
Function 04 – Read Input Registers
| Index | Description | Scale | Units | Data |
|---|---|---|---|---|
| 0 | Firmware Version | – | – | High Byte = Major Version Low Byte = Minor Version |
| 1 | Gas Sensor Type | – | – | 0x0000 = CO0x0001 = NO20x0004 = O20x0006 = H20x0008 |
= CH40x0009 = C3H8
2| Error Status| –| –| 0x0001 = End of Life (EOL) 0x0002 = (Reserved)0x0004 =
Sensor Not Installed 0x0008 = Invalid Calibration Values 0x0010 = Calibration
Expired 0x0080 = Warm-Up State
3| Gas Value| 10| Varies| 16-bit Value of Gas Measurement in PPM (CO/NO2), %
LEL (Combustible), or% V/V (O2)
Figure 8: Input Registers
Function 16 – Preset Multiple Registers
This function is used to write a block of contiguous registers in a remote
device. Sensor boards do not support this function. Relay boards support
setting both relay state and analog output value.
| Index | Description | Scale | Units | Data |
|---|---|---|---|---|
| 0 | Relay Board Outputs | – | – | High Byte = |
bit 7-4 (reserved)
bit 3 – Relay #4
bit 2 – Relay #3
bit 1 – Relay #2
bit 0 – Relay #1
Low Byte = 0 – 255 (8-bit DAC)
Figure 9: Output Registers
140 Long Road, Suite 101
Chesterfield, Missouri 63005
General Contact Information
Phone: 314-291-0440
Fax: 314-291-0646
Email:
customerservice@braschenvtech.com
Website: www.braschenvtech.com
Technical Support Contact Information
Phone: 314-291-0440 Option 2
Fax: 314-291-0646
Email: support@braschenvtech.com
Website: www.braschenvtech.com/support-for-existing-
systems
Revision: 3.0
Issue Date: July 16, 2024
Document Number: SG01
© Brasch Environmental Technologies, LLC
All Rights Reserved
SG01
Rev 3.0 – July 16, 2024
Brasch Environmental Technologies, LLC
140 Long Road, Suite 101
Chesterfield, Missouri 63005
314-291-0440
www.braschenvtech.com
References
- Home - Brasch Environmental Technologies
- Support for Existing Systems - Brasch Environmental Technologies