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Questions tagged [rs485]

EIA RS-485 is a serial communication standard using differential signaling.

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26 views

Wiring Connection from RS-485 to RJ-45 Port

I want to connect/wire from RS-485 A and B (only 2 pin) to RJ-45 port, anyone has the schematic diagram that show hows the wiring?
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1answer
47 views

How do you monitor communications on a positive-grounded device from a negative-grounded desktop?

I have a need to read the signals being sent between two boards in a lighting fixture. In preparing to do this I have read much about the chips, RS485, and analysers/decoders that are out there. I am ...
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2answers
97 views

RS485 vs RS232 similarity vs differences

I have used UART RS232 communication between MCUs extensively. Now I need to interface my STM32F407 MCU over RS485 bus with with devices. I have understood few things about RS485 but not-clear about ...
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2answers
76 views

Medium Range Two Wire Bus Recommendations?

Do you have any recommendations for a medium range (~10 meters) two-wire bus? My supply voltage is 24V and I'll have a single master with ~50 slaves connected to it. I've looked into: I2C - Great but ...
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0answers
22 views

Signal Attenuation TVS and series resistor

This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here. Are there some useful ...
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1answer
49 views

RS485 Rx signal connected with two drivers

I wonder why is RS485_Rx is connected with two line drivers while RS485_Tx is connected with only one line driver. Is this some mistake in the schematics or is it some standard circuit for RS485?
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2answers
50 views

Multiple MAX3485 on same UART

I am working on a project where I have 4 MAX3485 (for 4 different RS-485 channels) chips talking on the same UART bus with an ESP-WROOM32 module. This is the schematic: simulate this circuit – ...
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2answers
64 views

How to select the most appropriate (serial) bus for controller?

In the context of a robotic project where different 'payloads' and/or robotics arms (end-deflector) should be mated mechanically with power, data and control connections support, I would like to ...
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2answers
73 views

RS485 line protection diodes

Can anyone confirm the correctness of D27, D28 diode polarities or should they be in opposite direction? Please suggest an which diode is suitable for this purpose OR is it better to use a zener diode ...
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1answer
337 views

Does a MAX485 need decoupling capacitors?

I am designing a small device with two MAX485 chips. Do they need the decoupling capacitors on the 5V power?
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2answers
70 views

RS-485 Stub Connection Best Practices

I have a system with an RS-485 bus master and up to 12 slaves. The master and slaves are located in different assemblies and are connected with an RS-485 bus that is inside a cable harness. The cable ...
0
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1answer
54 views

Is it acceptable to have A & B wire at same voltage in RS485

I'm trying to implement DMX with a Raspberry Pi after reading this page: https://www.element14.com/community/groups/open-source-hardware/blog/2017/08/24/dmx-explained-dmx512-and-rs-485-protocol-detail-...
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26 views

DMX protection circuit (diode clipper)

TL;DR I’m building a board that bridges the common types of DMX connector (various forms of XLR, RJ45, tails and product-specific terminals). There is a possibility that someone could accidentally ...
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1answer
53 views

To Fail-Safe or not Fail-Safe on RS485/422 Transceiver

I'm stuck on a PCB design issue. I'm designing a new PCB (Daughter board) that will plug (via DB15-F to DB15-M) onto another PCB (existing Mother board) and the design intent is to take (from the ...
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1answer
69 views

Wireless or wired solution for perimeter fence security?

We are currently working on a project where we would like to place around 350 vibration sensors on our university's perimeter fence for security. The field layout is almost 1km to 1km (square - 1km^2 -...
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1answer
82 views

Rs-485 isolation

Hi, I have RS485 communication circuit as shown in figure. But it has no isolation, only SM712 is used for ESD protection. Now, i think it will be better to isolate the it.So, how can i isolate it? ...
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0answers
105 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 ...
2
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2answers
59 views

RS485 termination

What is the recommended way for termination RS485? I read about couple of options to do this. If I don't want to do dissipate extra power, can I just put 120 Ohm resistor? I saw the follow ...
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0answers
50 views

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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5answers
72 views

RS485 IC Termination Resistor Configuration

I've made a mistake on a design, that went into production... It was built like the drawing on the left, with R702 to 5V and R703 to GND, it should have been backwards... like the drawing on the ...
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1answer
29 views

Low current rs485 and wake up

I have the following question: I have to do a network of devices based on MCU. This network in a RS485 and the device is battery powered. For save the battery I put in sleep mode the MCU and I ...
0
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2answers
59 views

LIN to RS485 and back to LIN

I am currently communicating between two microcontrollers using a single pin and the LIN protocol over a short distance of 0.2m. Now I would like to extend the distance up to 5m by differentially ...
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3answers
152 views

ground connection for isolated rs485 [closed]

Is it necessary to connect isolated grounds for 2 different isolated RS485 nodes? For instance the following isolated RS485 breakout board doesn't have any GND connection in the board. https://www....
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2answers
268 views

Connect RS422 interface with Arduino Uno

I have a fishfinder,Lowrance Carbon HSD 7, and I want to connect it with the Arduino Uno to let the fishfinder transmit the Sonar data and GPS data via NMEA0183. According to the maker's site, the ...
0
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1answer
111 views

ModBus Timeout Error

Anyone very experienced with Modbus & RS-485??? My task is to control a DC motor using micro PIC24. The motor setting like the angle, delay, start/stop, duty cycle, etc will be sent from PC using ...
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1answer
95 views

RS485 Waveform while Receiving Data

I was testing the RS485 Circuit, below is my circuit and I connect J5 to my PC using another RS485 to USB converter. In PC through Modscan software I was monitoring the polling and response, a twisted ...
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2answers
51 views

I need to switch between RS485 signal and Digital input port

I am looking for a solution where I can use RS485 along with the 2 (two) digital input port on the same line but both will be used one at a time. When there is RS485 communication (selected through ...
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1answer
92 views

MAX485 suddenly drawing too much current and output voltage levels are not right

I have two PCB that I designed and they are made by a PCB manufacturer (so they are identical). They use a MAX485CSA to communicate but suddenly one of them is drawing too much current, on a normal ...
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2answers
49 views

Differential signal isolation

In differential signal circuits (specifically, RS-485), there is usually an isolation between the signal processing / generation stage (eg, microprocessor) and the line driver chip (something like a ...
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1answer
77 views

RS-485 works when USB powered, not when main powered

I'm thinkering with a RS-485 connection (modbus) to read out my electrical power meter. The setup is as follows: ESP32 --> MAX3485 --> RS-485 to USB when the ESP32 is powered via USB, on the same ...
0
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1answer
49 views

Arduino RS485 Communication

Working on a RS485 IC circuit. It is a point to point communication between two devices connected to each other via MAX485 IC and CAT6 Cable. At 1 or 2 m length of cable, the data transfer seems ...
0
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2answers
99 views

How to determine the physical location on a RS-485 daisy chain / bus topology?

I am trying to build a "daisy chain" using several Arduinos and MAX485 transceivers. All boards have a temperature sensor attached to it. A 9V battery supply all boards in the chain. I am trying to ...
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2answers
61 views

Where to use CAN v RS485

Not sure whether this is too broad a question but... Why would one choose CAN Bus over RS485, or vice versa, as a system interconnect? I have a MCU SBC with multiple interfaces including the two ...
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2answers
139 views

RS485 transceiver design

I'm working on a TTL to RS485 transceiver which is part of a bigger project (arduino based) and I came up with the following design: I have a few questions: 1) I have seen very different values for ...
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0answers
35 views

Addressable RS485

I have a requirement to take a board that interfaced with RS232 and put it on a half duplex RS485 bus. The obvious problem is that at the very least the board firmware will need to be altered to be ...
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0answers
54 views

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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1answer
126 views

What is 8 pin tssop packed component?232/485 ethernet converter

-size = 2.9mmx3.1mm -GND pin = 1,6,7 connected -7.pin 4.7uh connected
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2answers
75 views

What communication method shouild I use [closed]

So I wan to control a bunch of devices. I though first of using RS485 but after some digging I figured out this might not work as I don't really have a pure daisy chain. The configuration I would like ...
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3answers
81 views

MAX485 Receive Output pin current sufficient for optocoupler LED?

I want to recreate a project found at this link where an optocoupler's LED is a driven by the receiver output of a MAX485. Now, my question is, the LED series resistor (R5) value is 470ohms, if my ...
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2answers
56 views

How to deal with signal polarity relative to USB-RS485 converters?

I have two USB-RS485 converters. One with skrew connectors that are electrically isolated from the USB (ADAM-4561) and one wire-end version from FTDI chip. I want to connect them together to send ...
6
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2answers
212 views

Purpose of this oscillator (74HCT14-based) on RS-232 to RS-485 converter?

I am reverse engineering an RS-232 to RS-485 converter to understand how it works. I have attached the schematic that I reverse-engineered from the PCB (apologies for the hand-drawn schematic). I've ...
1
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1answer
229 views

How to make a circuit for DMX splitter notification LEDs?

I am trying to make a DMX splitter. Everything works now, but it would be somewhat useful to have notification LEDs, like in the example below. For the input I could use one LED, which I either ...
0
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1answer
180 views

Trying to power 100 Arduinos from single power line

I'm trying to power up to 100 Arduinos that will be spread across a 25m wall using a single power line. The idea is each Arduino will have a few a few buttons, leds & an oled screen and will all ...
7
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4answers
209 views

RS485 minimum node spacing - 3 x RS485 device on PCB

I would like to ask something about RS485 minimum node spacing which is described in (Page 5) TI Design guide I would like to create device which consists from 3 existing RS485 devices. My plan was ...
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1answer
358 views

MAX487CPA/SN75176BP RS485 IC gets too warm (in DMX Splitter circuit)

Brief I built part of the scheme below (input K2/IC5, optocoupler IC9 and output IC6/K3). IC9 is overheating when I connect LED pars to K3, because voltage is flowing back into pin 6/7. If I connect ...
0
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1answer
162 views

Wire to VDD or GND?

In the circuit below, there are four LTC485 ICs, one input (left), three for output (right). Pins 2, 3 and 8 are going to +5V, as well as GND. So where should I connect them to? Should I wire them all ...
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1answer
59 views

How to find RS485 UART pins are inverted in the data sheet?

I want to know, how we identify the RS485 pins are inverted. I am using at91 microcontroller? This sam9260 board has four rs485 in which two of them are inverted. ...
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1answer
68 views

Mega2560 master on RS485 bus stops communicating with VFD when I add another RS485 module

I’m doing a project where I’m building a control panel for a VFD (inverter/variable frequency drive). I’m connecting the two over half duplex RS485 and use Modbus RTU. As a master I use a Arduino Mega ...
0
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1answer
163 views

RS485 to RS232 conversion?

I need to connect a sensor that uses a RS485 transmission to RS232 or something I can read through the com ports on my data logger. I can't use usb ports or virtual com ports due to the program I am ...
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3answers
678 views

RS 485 ground signal and chassis

I have a shielded twisted pair running from one device polling several devices in an RS 485 loop. The conditions: The devices are in parallel as they should be. The termination resistors are in ...