Questions tagged [rs485]

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

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Choose between Profibus PA and DP

I currently try to understand a new technology: Profibus, until now I worked with HART, with which I also had some struggle in the begging but now it's clear. I try to understand why in a factory is ...
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43 views

Overvoltage protection RS485 inputs

The finished apparatus is supplied with 48V nominal ac (37V to 57V), and now I'm looking to design it so that it isn't destroyed if a technician accidentally connects the supply 48V +/- to the RS485 ...
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42 views

differential input overvoltage protection

some suggestions to protect an RS485 from differential input overvoltage? I want protect the transceiver RS485 if the differential input voltage is below -7V or above +12V. Someone does anyone know ...
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66 views

protect RS485 from PoE

I have a board with two RJ45 connectors. One is used for an Ethernet port and the other one is for a RS485. The Ethernet is for Power over Ethernet. What are some suggestions to protect the RS485 port ...
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39 views

MAX3485 pull-up pull-down resistors

I want to use the following MAX3485 chip: https://datasheet.lcsc.com/szlcsc/2006181334_UMW-Youtai-Semiconductor-Co-Ltd-MAX3485ESA_C668204.pdf I do not speak any chinese, but my question is more in a ...
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Is it OK to use RS485 with separate wires for each device?

I know common use of RS485 is top wiring diagram. But in my project we need to use RS485 for extend range and reliability connection but connection will be bottom wiring diagram. Can I use a single ...
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51 views

Using digital and analog signals in the same cable

I am working on a project with 3 PCB : PCB1 is the master, it communicates with two slaves, PCB2 and PCB3. PCB1 is powered by a battery and it redirects the supply to PCB2 and PCB3. Each PCB includes ...
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156 views

How to interface a RPi Pico to DMX / RDM

Years ago, I was looking at creating a stage DMX controller using AVR. Time moved on and the Raspberry Pi Pico has now been released. I'd like to revisit the project using a Raspberry Pi Pico, which ...
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10m wired connection: I2C Repeater or RS485 [closed]

I need a wired connection between one Master and several (5-10) slave devices. I've considered UART, SPI, I2C, RS232 and RS485. In the end, I've narrowed down the options to I2C with a repeater or ...
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34 views

Using an Ethernet Phy and XFMR instead of RS422

We've been using a quad RS485 setup for some time. No problems. Now we'd like to increase the speed over what we can get away with on RS485 with the micro we're using. Essentially, we've been ...
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Wiring RS485 - RFID

I am new to using this device, I trying to get the numbering of rfid iclass card with a HID reader (HID® iCLASS SE® R10) via usb converter rs485 (a COM port is generated in windows) I Try with this ...
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RS-485, 5Vdc and 24Vdc over a single Ethernet cable

I recently started to work on a project that involves motor drivers and microcontrollers in a network topology. This is rather a theoretical question, just something that I was thinking about. The ...
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485 does not work some times

in fact i have several boards like Analog barrier, digital barrier, uart barrier and power control. they are connected to together by RS485. but some times when some of 485 don't work of the RX led ...
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1answer
38 views

ESD protection for RS485 with power bus, without earth

On my board there is a 4-pin connector as follow: +24V DC (up to 6A) RS485/A RS485/B GND On the system there is no real earth, because there are no metallic parts (chassis, case, structure, etc...). ...
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45 views

Is the RS485 common mode output voltage supposed to be only 3v

I am designing an RS485 driver to connect to an ESP32 using SP3485 from Max Linear. I understand that the differential output is 3v and not +7v and -5v like the RS485 spec stipulates. Are there some ...
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Star configuration using CAN Bus, I2C or RS485

I need to create a sensor network, with a central node receiving data from +10 different nodes, each one +20meters from the central node. So basically I need to create a star configuration, with a ...
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45 views

Implement RS485 or I2C protocol using the usb-c connector?

I was wondering if there's any reason why I can't implement RS485 or 12C communication on the data pins of the USB-C connector? I can't find anything on the internet that tells me not to.
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RS485 isolated circuit - forgot connections. Will this work?

below is my schematic for isolated RS485 section. FYI B0305XT-1WR2 is used for power isolation and ISO1500DBQ as transceiver. As you can see I forgot to place GND & GND_RS485 connections at pins 2 ...
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Terminating resistor considerations for half-duplex RS-485 over 80-200 m cable at 115 kbps

I'm designing a system where we are communicating with a device (ultrasonic anemometer) which is at the end of a cable which could vary between 80-200m. The sensor communicates via RS-485 half-duplex. ...
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52 views

The Best Place for the Reverse Polarity Protection Diode

I have several RS485 devices. All of them are connected together and power by a 12V power supply. Each device has its own 5V voltage regulator. I want to use diodes for each of them to protect aginst ...
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1answer
127 views

CAN Bus with RS485 CAN HAT for Raspberry PI

I have set up a CAN bus between 2 STM32 Nucleo's, where one is only sending messages and the other one is only reading them. This works, I have also validated this by connecting them to another CAN ...
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39 views

RS485 unmatched line - what will be the impact?

I am doing an experiment where I have a computer with an rs485 transceiver on it and data rate of 1Mbs. an rs485 30m long with Z0 of 120ohm (also have one with Z0 100ohm). at the end of the cable I ...
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1answer
81 views

Using RS485 over CAT5e Foiled Twisted Pair (FTP)

I'm planning a system that has two sub systems that need to communicate with the PLC via RS485. The baud rates are 9600 and 19200 bps. The cables are static (i.e. not moving) and placed inside of a ...
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42 views

USB Solution to Bit Bang RS485 at a high Baud Rate

I am searching for a solution to write a ~800 byte data stream at a 10K baud rate from a USB device. This is going to connect to a piece of hardware that uses a RS485 connection which expects an ...
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RS485 Communication Issue Adm2483

I have Setup like this for my application. I have Transformer which gives out 12V 1A & 5V 500mA output.I have used isolated ADM2483 design where power galvanized isolated. Primary side 5v &gnd ...
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86 views

RS485 burnt slaves after short-circuit

I have a question regarding a scenario I found myself in, hoping that someone can clarify if the scenario I'm going to illustrate is possible (short premise: I'm a programmer, I'm not an electrician ...
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57 views

Transmission lines in paralell for RS485

I have a system with two RS485 transceivers connected by a 300 meters long cable, with 6 wires inside it. In this case, 3 paralell wires of this cable are being used for the "A" signal and ...
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54 views

how to connect PIR sensor to arduino using RS485

I have to connect PIR sensor HC-SR01 to Arduino using RS485 such that PIR sensor's TTL signal gets converted to RS485 while transfer and gets converted back to TTL while receiving on Arduino side. ...
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55 views

how to verify truth table of MAX485/RS485

I want verify 2nd case of the below truth table of MAX485 IC (RS485). Please see in red color. Is my circuit correct ? I have connected RE,DE and A-B to GND for making it LOW.I have connect DI to GND ...
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94 views

RS485 implementation using MAX485 chip

I am using MAX485 chip for serial communication. But a weird behavior I found which I can not explain. Can any one help me in understanding why LED is ON in Receiver pin (RO) when I have not given any ...
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64 views

Bus communication scheme for large number of devices (255+ nodes)?

I'm trying to figure out the feasibility of setting up some type of differential bus communication for up to 400 devices outdoors. The main constraints are mainly power consumption, complexity, wire ...
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71 views

How to identify the polyfuse used in this RS-485 module

This is the popular RS-485 module found in the market, how can I identify the polyfuse/heat recovery fuse in it? Also its manufacturer or electrical ratings?
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59 views

RS485 communication issue

I have used PIC18F45k40 device for RS485 communication. I have 2 ckts one is isolated and another non isolated RS485 design. I have schematic & placement for reference. I have connected multiple ...
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1answer
40 views

RS485 Communication- board Hangs

I am using isolated RS485 for communication. MCU & RS485 IC communication is through UART. IC supports 500kbps datarate Configuration a) Baud rate- 460800 b) Every 0.1s I am sending 288bits data ...
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57 views

Grounding in CAN / RS485 Busses

I'm interested in how to properly realize Grounding in a CAN / RS 485 bus setup. From my understanding, when non-isolated transceivers are used, in addition to the differential signal lines, a third ...
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134 views

RS-485: what happens when bus contention occurs

I'm refering to an half-duplex RS485 application which consists of a master and multiple slaves like in the circuit below (I'm using an ST3485). simulate this circuit – Schematic created using ...
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RS 485 communications not working, A, B both low

My question is: for RS485, does A or B (one of the two) have to be HIGH by default? If there are only 2 communication nodes in the network, should one of the nodes pull A or B (one of the two) HIGH by ...
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28 views

Sharing Isolated Power supply for CAN and RS485

I am using ISO1432 from TI for isolated RS485 transceiver function. And ISO1042 for Isolated CAN transceiver. Both devices requires an isolated supply on bus side. Can I use one isolated 5V DC-DC ...
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Communication within 5-10 meters: RS-485 or Wireless?

As a follow-up for my previous question, can anyone please recommend for my application (communication between two floors of a building) as whether to use RS-485 or any wireless technique (I am ...
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Transmitting VCC and GND signals for use with RS-485

The specific question I want to ask is whether I can transmit VCC(5VDC) and GND power signals for powering the destination circuit (in an RS-485 arrangement) or not. The power lines will be grouped ...
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54 views

Why Arduino not receiving RS485 data?

I am trying to send data from Arduino mega (message "ping") to Arduino nano, then send back (message pong) to the mega board, I am not receiving "pong" back to the mega board, why ...
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58 views

RS485 over CAN: when and why?

I'm designing my own home automation gateway and I've already added a rs485 transceiver, everything is fine, but I'm thinking about adding also a CAN bus transceiver because I've seen that it's often ...
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144 views

Pull-up and pull-down resistors for RS-485 TTL I/O pins

I'm Using a THVD1451 for full-duplex RS-485 communication. In Datasheet, for transient protection against surge transients, it's recommended to use the circuit below: In this circuit, there is a pull-...
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49 views

where should I place the terminations resistors for RS485?

I want to add termination resistors in RS485 bus . My systems is Multi-point ( the MCU can send to/receive from 3 external devices) I found out from this RS-485 CABLE SPECIFICATION GUIDE. that I need ...
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42 views

What is the max current consumption on bus side of isolated RS485?

application - 10 nodes 1 meter apart 120 Ohm terminating resistors at last node and 1st node i hope to use ADM2486 data rate 10-17Mbps vdd1 5V and isolated vdd2 5V what is the max current consumption ...
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53 views

withstand voltage of RS-485 Transceiver

i am working with a half duplex RS-485 Transceiver ic SP3485EN with 10Mbps Data Rate datasheet :https://www.maxlinear.com/ds/sp3485.pdf i actually want the maximum working voltage (Viom) of design ...
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73 views

RS485 USB converter driver polarity

I have an RS485 USB converter connected with a temperature controller in the controller's datasheet it says that the 12 is (+) and 11 is (-) and in my USB converter there is A and B Am not sure the D+...
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51 views

Generate spikes on RS485 bus

I was thinking to build some test equipment for a RS485 bus, but Would like to get some suggestions on how I can introduce bursts of spikes in a "safe" way without damaging the connected ...
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1answer
36 views

Isolating an existing RS485 tranceiver

I have a heat pump with an RS485 interface. Via a simple RS485 chip. No isolated interface, no isolated power supply to it. I want to add a power meter at 400+ meter to it and want to properly isolate ...
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2answers
106 views

Bi-Directional RS-232 / RS-485 translator using MAX3162 IC [closed]

I'm trying to communicate with an I2C bus using the Serial Card in my PC (NI PCI485/8). I've created a circuit using the MAX3162 to translate from RS485 to RS232. Then I use the MAX3232 as a level ...

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