Questions tagged [modbus]

Modbus is a serial communications protocol commonly used by PLCs (programmable logic controllers) and other industrial control systems. While originally based on traditional serial communications many extensions exist to allow communication over other networks such as TCP/IP.

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RS485 registers for calculating total power consumption (kwh)

I have an energy meter (OHIO A2000) which has been now discontinued by the manufacturer. Anyway, I'm following the manual for extracting energy parameters through Modbus RS485 communication. I'm ...
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Looking for data sheet of the following Modbus Sensors #updated

I'm a noob in this area, please ignore any stupidity and lack of info and any help is appreciated and I'm ready to provide all clarification on the post if by chance any info is missing. So i have ...
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311 views

Is there a fieldbus with more than 250 nodes per segment?

We plan to realize a sensor cable several 1000m long which has ideally every 1-2m a magnetic field sensor on a small 10x30mm platine with microprocessor/FPGA for DSP and I2C on chip communication. ...
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watchdog timer on PLC

I've currently set my PLC as a modbus slave, and written some python code which connect to it and act as a modbus client. I am having some problems with the modbus server sometime terminating the ...
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1answer
172 views

Why is there no reponse from ModbusRTU slave using converter?

There are two devices: Eaton EM20/M (~like Northern Design Cube 400) Volison ADM-5850G Connected them like: Trying to get data from EM20/M which supports ...
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40 views

Interface PID temperature control module using Arduino

I need to interface a modular type temperature controller using Arduino. This is the datasheet of temperature controller The datasheet mentioned like this, My questions are, How can I interface( ...
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372 views

Modbus RTU for FPGA

I need to implement Modbus RTU in FPGA (Cyclone 3). Basically I see two ways to do that. The first one is to hardcode it in VHDL and it doesn't seem to be that hard at the begining. But I have looked ...
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244 views

libmodbus modbus_read_bits() returns illegal function

It is all okay when it comes to read registers with: modbus_read_registers(ctx,0,32,destination); It gives me values of 32 different registers. But when it comes ...
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2answers
385 views

Modbus communication between Arduino and Unitronics Jazz2 PLC

I am trying to connect Unitronics Jazz2 PLC (JZ20-R16) and an Arduino Uno using Modbus protocol, over RS232 interface. I've got all the required connectors for both Arduino (TTL-RS232 MAX3232 ...
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210 views

Modbus RS485 trouble

I'm trying to connect a power meter (http://www.ebay.co.uk/itm/272572704122) with Modbus over a RS485-USB converter (http://www.ebay.co.uk/itm/231570466384) The converter looks like a serial port (<...