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Master Click PLC Communication: Ignite your Modbus RS485 passion!
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Jan 9, 2025
90% of industrial automation systems use Modbus for communication. This open standard protocol is used for everyday applications, including monitoring and controlling equipment such as PLCs (Programmable Logic Controllers), remote terminal units, sensors, and more in automation and process control environments. RS-485 typically utilizes twisted pair cables, which consist of two insulated copper wires twisted together. This configuration helps to reduce electromagnetic interference (EMI) and crosstalk from external sources, ensuring a more reliable signal over long distances. Peer-to-peer (P2P) communication is a decentralized communication where two or more devices connect directly to share data or resources without needing a central server. Using the Modbus RTU Serial Protocol, we will connect two Click PLUS PLCs through RS485 in a peer-to-peer fashion. We will share the following information between the two PLCs: One hundred individual bits (0/1—On/Off) will be written and read between the controllers. We will also share ten words (16-bit), which will also be written and read between the PLCs. In this manner, the individual controls can see all the data from each other. Let's get started. More information can be obtained at our website. This includes all of the links mentioned in this video. https://accautomation.ca/mastering-click-plc-communication-modbus-rs485/ 00:00 Mastering Click PLC Communication Modbus RS485! 01:41 Wiring Click PLC RS485 Ports 04:20 Click PLC PLUS Client (Master) Modbus RTU Program 13:40 Click PLC PLUS Server (Slave) Modbus RTU Program 16:57 Monitoring the Click Modbus RTU RS485 Network using Data View 19:44 Creating a Heartbeat for Modbus RTU Serial Communications 26:28 Monitoring and Resetting the Modbus Client Communication Previously, we looked at the following: Click Plus Software Installation https://accautomation.ca/click-plus-software-installation-version-3-00/ https://youtu.be/6uQQzyZ-O3s Establish Communication https://accautomation.ca/click-plus-establish-communication/
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0:03
90% of industrial automation systems use
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modbus for communication this open
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standard protocol is used for everyday
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applications including monitoring and
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controlling equipment such as plc's
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programmable logic controllers remote
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terminal units sensors and More in
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Automation and process control
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environments rs45 typically utilizes
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twisted pair cables which consist of two
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insulated copper wires Twisted together
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this configuration helps to reduce
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magnetic interference Emi and cross talk
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from external sources ensuring a more
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reliable signal over long distances
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peer-to-peer or PTP communication is a
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decentralized communication where two or
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more devices connect directly to share
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data or resources without needing a
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central
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server using modbus rtu serial protocol
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we will connect two click plus PLC
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through rs45 in a peer-to-peer fashion
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we will share the following information
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between the two p L C's 100 individual
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bits IO or on and off which can be
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written and read between the controllers
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we will also share 10 words 16 bit each
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these will also be written and read
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between the plc's in this manner the
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individual controls can see all the data
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from each
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other the following summary table will
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show the
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relationship let's get
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started detailed information contained
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in this video can be found at ACC
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automation. a a link has been put in the
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description below if you have not
1:33
watched the other videos yet there'll be
1:34
links in the description below that will
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start you a video one they be links the
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rest of videos in the series as
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well wearing click PLC rs45
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ports rs485 is a standard defining the
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electrical characteristics of a balanced
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differential Digital Signal system
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commonly used for serial communication
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industrial environments and
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long-distance applications the physical
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media for rs45 communication has several
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key
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characteristics twisted pair cabling
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rs45 typically utilizes twisted pair
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cables which consists of two insulated
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copper wire Twisted together as
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previously mentioned this configuration
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helps reduce Electric magnetic
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interference or Emi and cross talk from
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external sources ensuring a more
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reliable signal over long
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distances balance differential signaling
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the balance differential signaling used
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in rs45 transmits data over two wires
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often called A and B lines the
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difference in voltage between the two
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lines determines the binary data being
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transmitted making it less susceptible
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to noise and allowing for longer
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communication distances up to 4,000 ft
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or
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more impedance the characteristic
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impedance of rs45 cabling is typically
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around 120 ohms matching the impedence
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of the cable and the connectors is
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critical to prevent signal Reflections
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that can lead to data loss or
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corruption termination resistors rs45
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systems of to employ termination
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resistance typically around 120 ohms at
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both ends of the communication line to
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reduce signal Reflections at the end of
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long cable
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runs shielding shielded twisted pair
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cables can be used in environments with
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high Electric magnetic
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interference The Shield provides
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additional protection against external
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noises providing the reliability of data
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transmission
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although rs45 does not specify a
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connector type standard options depend
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on the application include DB9 db25 and
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terminal blocks the choice of connector
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can affect the ease of installation and
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overall reliability of the
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connection the physical media of rs45
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communication is designed to enable
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reliable and robust data transmission
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over extended distances making it a more
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popular choice in various Industrial
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Automation applications
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[Music]
4:01
our click plcs have a terminal
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connection on Port three of the CPU we
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are wiring the plus terminal to the plus
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terminal and the negative terminal to
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the negative terminal using a twisted
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pair cable two wires additional devices
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can be physically wired by daisy
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chaining them in
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series click PLC plus client master
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modbus rtu
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program call up the click programming
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software we will now create a program to
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control all the information on our rs45
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modbus rtu Network select the connect
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icon on the Home
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tab the connect to click PLC window will
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be
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displayed the program will look at your
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network and Report the available PLC
4:44
Connections in our case we can see the
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two different plc's there are three
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connections because of the Wi-Fi setup
4:51
on the one PLC and the ethernet port on
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both if you are unsure of the correct
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connection select blank run and error
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LEDs this will flash a light so you can
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determine the PLC for the connected
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selected select
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connect the connection status will be
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displayed at the bottom of the software
5:12
window we can also highlight our logic
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by selecting the status icon on the Home
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tab select comp Port setup under the CPU
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icon on the Home tab this will open the
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window displaying all available ports on
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the controller select setup for Port
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three
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this is the rs45 communication Port the
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port details will show you the setup for
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the physical
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communication the protocol will be set
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for modbus we will leave the node
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address as a default the parameters will
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also be left as their default 38,400 bod
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odd parody One Stop bit and eight data
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bits we will also leave the advanced
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configuration for timeouts and response
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delays as their default select
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okay on the Home tab under CPU select
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system Sy configuration this will show
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you the physical PLC and the associated
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inputs and outputs we have
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connected give this PLC a name under the
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PLC name this will help us determine the
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PLC we are communicating with in the
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future we will name our ACC client
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select
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okay since we changed the configuration
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we must write the program to our PLC
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controller
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we can now save the PLC program with a
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name we will
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remember select save
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we will now start the ladder Logic for
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our rs45 modbus communication right
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click sub routine program in the
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navigation window and select add new sub
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routine program this can also be done by
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selecting the shortcut Control Plus
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U we can now name our new sub routine
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communication rs485 will be used as our
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name select okay a quick guide for a sub
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routine program will be displayed select
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okay
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the first one will have the first scan
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SC2 used to trigger the first sand
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communication
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instruction CPU Port 3 will be set for
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our communication port for the send
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instruction the protocol will be modbus
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we previously looked at the comp Port
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setup but if you don't know the
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parameter set we can look at them again
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using this
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button the slave ID for the serial
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device will be set to one and we will
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write multiple coils function code 15
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click addressing will be used for the
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addressing
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type C1 will be the starting slave and
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starting Master address we will write
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100 bits of
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information status Flags play an
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essential role in the serial
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communication method we will use these
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flags to trigger the next communication
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instruction the following communication
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instruction Flags will be trigger the
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next Etc here's a timing chart for the
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send the
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command assign a bit to each status flag
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and register for the communication
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instruction status code we will use the
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address picker to document these words
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and bits which will help us to continue
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to program
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[Music]
9:15
Rong two will now be used the normally
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closed sending flag with the Leading
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Edge of the send success and send error
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to trigger the receiving instruction
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we do not care if the send was
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successful we want to keep the
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communication
9:37
going the receive instruction will use
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CPU Port three of the modbus protocol
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with the slave address ID 1 we will read
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the coil status using click addressing
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the starting slave address will be c101
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and the starting modbus address will
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also be
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c101 just like the send command we will
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read 100 bits of information
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set and document the status Flags so we
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can use them to trigger the next send
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word instruction
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[Music]
10:25
[Music]
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rung 3 will use the status flags from
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the receive instruction to trigger the
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next send instruction the normally
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closed sending flag with the Leading
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Edge of the send success or send error
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triggers the send
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instruction copy the previous send
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instruction and we will change the
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modbus function code to write multiple
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registers
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16 10 Master addresses starting at DS1
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will be sent to the slave address
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starting at
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DS1 status flags are set and documented
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for the next receive instruction
11:15
[Music]
11:22
[Music]
11:37
the status fles from the previous
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instruction send write register
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instruction will trigger the final
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receive read register
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instruction copy the last received bit
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instruction
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and we will change our modbus function
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code to the read holding register
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03 the starting address for the master
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and slave will be set for
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ds11 we will read 10 words or register
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addresses setting the status flags and
12:14
document for this instruction will
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trigger the first send instruction at
12:17
Rong one
12:32
remember to save your program often as
12:34
you program this will ensure you do not
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lose any work if your computer
12:53
crashes place a return instruction at
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rung five for our communication sub
12:57
rutine you can see that we are just
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using the modb read and write commands
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in
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series the status flags from one
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instruction trigger the next the final
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instruction status Flags trigger the
13:08
first and we start the communication
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again this method of communication
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ensures the quickest system
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response returning to our main program
13:17
under the navigation window we can use
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the call instruction to execute the
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communication sub routine every
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scan save and write the program to The
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Click plc
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click PLC plus server slave modbus rtu
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program call up the click programming
13:53
software we will now create the program
13:55
to control all the information on our
13:57
rs45 modbus rtu Network on the startup
14:00
window select connect to PLC the connect
14:03
to click PLC window will appear the
14:06
program will examine your network and
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Report the available PLC
14:11
Connections in our case we will see two
14:13
different plcs are existing ACC client
14:16
can be seen for our Wi-Fi and ethernet
14:18
connections there's also another PLC
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with no name select this
14:22
controller if you are unsure of the
14:24
correct connection select blink run and
14:26
error lights this will Flash the light
14:29
so you can determine the PLC for the
14:31
connection selected select
14:34
connect we will read the PLC program in
14:36
our click
14:38
controller the connection status will be
14:41
displayed at the bottom of the software
14:42
window we can also highlight our logic
14:44
by selecting a status icon on the Home
14:47
tab on the Home tab under CPU select
14:50
system configuration this will show you
14:52
the physical PLC and Associate inputs
14:54
and outputs we have connected give this
14:56
PLC a name under the PLC name this this
14:59
will help us determine the PLC we will
15:01
be communicating with in the future we
15:03
will name ours ACC server select
15:07
okay save the PLC program with a name so
15:10
we will remember it in the
15:17
future select
15:21
save select comp Port setup under the
15:24
CPU icon on the Home tab this will open
15:27
the window displaying all available
15:29
ports on the controller select setup for
15:31
Port three this is the rs45
15:33
communication Port the port details will
15:36
show you the setup for the physical
15:38
communication the protocol will be set
15:40
for
15:41
modbus we will leave the node address as
15:43
the default one the parameters will also
15:46
be left as their default 38,400 bod odd
15:50
parody One Stop bit and 8 bit
15:53
communication we will also leave the
15:55
advanced configuration for timeouts and
15:57
response delays as their default
15:59
select
16:00
okay since we changed the configuration
16:03
we must write the project to our PLC
16:23
controller returning to the click client
16:26
we will stop and start the plc this will
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start the communication with the first
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scan flag you will now see the LED
16:33
lights blinking on our click
16:57
server monitoring The Click modbus rtu
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rs485 network using data
17:05
view under the monitor heading in the
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program tab select data view this is in
17:10
the click programming software
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navigation
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window right clicking this data view
17:15
window and selecting rename will allow
17:17
us to rename it double clicking on the
17:20
new title will display the data View
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Window the data view window will display
17:26
we can now enter our bits and words we
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want to monitor for the rs45 modbus
17:31
network if we need consecutive addresses
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we can quickly enter them by selecting
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the last address and pressing control
17:37
enter we will display 10 bits and words
18:01
[Music]
18:03
finally we should save the program so
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our data view information is
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saved call up the data view information
18:09
for the click server on our modbus
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Network enter the same address as the
18:13
click client
18:30
[Music]
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save the program
18:49
[Music]
19:04
as you write the bits and words in the
19:06
data view window for either the client
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or the server the corresponding bits and
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words will be changed in the other our
19:13
communication is
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working however if communication is lost
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the programs will no longer share
19:20
information and a controller will not
19:21
know how to recover the in continued
19:24
communication we will now examine how to
19:26
correct and program this
19:29
if you're enjoying this video please hit
19:30
the like button below keeping up with
19:33
all the latest automation Innovations
19:34
can be difficult so hit the Subscribe
19:36
button remember to hit the Bell beside
19:38
your subscription to actually receive
19:39
those
19:43
notifications creating a heartbeat for
19:45
modbus rtu serial
19:51
Communications a heartbe bit will pulse
19:53
on and off on our Network for a Time
19:55
duration this can be used to determine
19:57
if Communications or working or not our
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herbe bit will turn on for one complete
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send and receive instruction sequence
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and then turn off for another complete
20:07
send and receive instruction
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sequence we will add this heartbeat bit
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pulse at the end of our communication
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sub
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routine when the Leading Edge of our
20:17
last communication instruction is
20:19
triggered this will set an internal bit
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C1 1900 on
20:35
when this internal bit is on and the
20:37
heartbeat bit c100 is on c100 and C 1900
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are reset
20:49
[Music]
21:06
when it's internal bit is on and the
21:07
hary bit c100 is off set c100 and reset
21:12
c1900
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as you can see the heartbeat bit will be
21:38
triggered on and off with the Leading
21:39
Edge or our last communication send
21:48
flag using the address picker and the
21:50
click programming software we can
21:52
document the heartbeat and work bits for
21:53
this circuit
22:49
returning to the click server program we
22:50
can program the heartbeat bit logic we
22:53
will use a timer to determine the
22:54
communication throughput on our modbus
22:56
rs45 Network and weather communication
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is
23:06
lost the trailing edge of the heartbe
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bit will copy the timer representing the
23:11
communication throughput into our
23:12
storage area
23:19
ds100 the c100 harpy bit will then be
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used to determine the condition for
23:24
timer one which will have a set point of
23:26
10,000 milliseconds or 10
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[Music]
23:44
seconds the communication output error
23:46
will be activated when the last
23:48
communication timer is greater than 200
23:50
milliseconds
24:00
remember to save and document as you
24:01
program the controller
24:16
[Music]
24:24
[Music]
24:58
our heartbeat circuit for our server now
25:01
counts for when the heartbeat bid is on
25:03
we must also create Logic for when this
25:05
bid is
25:06
off when the c100 heartbeat bti is off
25:09
it controls a second timer with the same
25:11
preset as the
25:19
first if this timer exceeds 200
25:21
milliseconds the output aor bit will
25:23
also turn
25:27
on document save and transfer the click
25:30
modbus rs45 server program to the
25:46
[Music]
25:55
controller when testing the heartbeat
25:57
circuit up the server PLC we can
25:59
disconnect the rs45 communication and
26:02
the output will turn on indicating an
26:11
error putting back the connection will
26:13
restore the communication
26:29
monitoring and resetting the modbus
26:31
client
26:34
communication our current click client
26:37
program starts only on the first scan
26:38
bit we will modify it to detect a
26:40
communication error and reset it using
26:42
two timers we will start the first timer
26:45
using the knot of the last sen bit flag
26:47
instruction and the second timer each
26:50
timer will have a preset value of a
26:52
th000 milliseconds or 1 second
27:03
the output of the first timer will start
27:04
the second
27:14
timer we can document the timers using
27:16
the address picker in the click
27:18
programming software
27:28
[Music]
27:37
we can now add the Leading Edge contact
27:39
of our first timer on the first Runk
27:41
when the communication sequence does not
27:43
execute within 1 second this bit will
27:45
trigger starting the communication
27:48
again the second timer is used to
27:50
continuously every 2 seconds 1 second is
27:53
for the first timer and then this 1
27:55
second is for the second timer we can
27:58
save and transfer our program then
28:00
moving back to the main program of our
28:02
client code we can add our program to
28:03
turn on an output when we detect the
28:05
communication
28:12
error if the first timer expires we will
28:15
activate the first
28:18
output document and transfer the program
28:43
we can call up both the DAT view windows
28:44
are both click programs and test our
28:55
Communications if you found this video
28:57
helpful check out our other videos on
28:59
PLC programming and don't forget to
29:00
leave our questions and comments
29:10
below zal communication over rs45
29:13
provides a versatile and robust solution
29:15
for industrial communication it
29:17
facilitates interruptibility between
29:20
various devices and ensures reliable
29:22
data communication over long
29:24
distances we have learned the importance
29:26
of modbus rs45 in PLC communication and
29:30
steps to set it up
29:34
effectively The Click PLC now has a
29:36
mobile app for control learn how this is
29:39
done
29:40
here our entire series on the click PLC
29:43
can be found here
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