Tag Archives: RS485

Isolated Power Supply for RS485, RS422, RS232, SPI, I2C and Power LAN

Mini Isolated Power Supply is designed for CAN, RS-485, RS-422, RS-232, SPI, I2C, Low-Power LAN applications. The power supply provides +/- 5.50 V DC symmetrical outputs with load current 500mA from 5V DC input. The project is built using SN6505A IC from Texas instruments. The SN6505A is a low-noise, low-EMI push-pull transformer driver, specifically designed for small form factor, isolated power supplies. It drives low profile, center-tapped transformers 5 V DC power supply. Ultra-low noise and EMI are achieved by slew rate control of the output switch voltage and through Spread Spectrum Clocking (SSC). The SN6505 consists of an oscillator followed by a gate drive circuit that provides the complementary output signals to drive ground referenced N-channel power switches. The device includes two 1-A Power-MOSFET switches to ensure start-up under heavy loads. The internal protection features include a 1.7A current limiting, under-voltage lockout, thermal shutdown, and break-before-make circuitry. SN6505 includes a soft-start feature that prevents high inrush current during power up with large load capacitors.

Isolated Power Supply for RS485, RS422, RS232, SPI, I2C and Power LAN – [Link]

PIC Arduino with RS485

This board created for makers, who wants to use various Arduino UNO shields using PIC microcontrollers from Microchip. Board facilitates the use of any 28 PIN SMD SO PIC microcontrollers without crystal (internal oscillator). Project also can be used to develop RS485 application with the help of on board SN75176 IC. Two regulators provide 3.3V and 5V DC outputs. ICSP connector provided to program the PIC IC using PICKIT2/PICKIT3 programmer. On board DC jack connector and additional CN2 Header connector helps to power up the board. Input supply 7V-15V DC. This board has been tested using PIC16F886 IC. Switch SW1 helps to reset the board. Please refer to PCB top layout for Arduino Vs. Microchip Pin configuration.

PIC Arduino with RS485 – [Link]

4 channel RS485 Remote Controller

4 Channel 2 core twisted pair remote controller built using PT2262, PT2272-M4 IC from Princeton technology and MAX485 IC from Maxim. PT2262 is an Encoder (Transmitter), PT2272-M4 Decoder (Receiver) and MAX485 works as bridge for twisted pair communication between encoder and decoder. The receiver provides 4 channel Momentary outputs. All outputs are TTL level and can be interfaced with other circuits or relay board. Transmitter works with 5V to 12V DC. Receiver works with 5V DC.

When any of SW1-SW4 (S1-S4) tact switches is pressed, power is applied to encoder IC and RS485 IC, the encoder starts scanning Jumper J1-J8 and transmitting the status of the 8 bits address and data serially. The decoder IC receives the data from MAX485 and compares it two times with J1-J8 address jumpers, also provides outputs high and at same time VT (Valid Transmission) LED goes On, if the data is Valid and address of Transmitter and Receiver are same. It is important to have same jumper settings J1-J8 at transmitter and receiver to pair both.

4 channel RS485 Remote Controller – [Link]

PIC Development Board for RS485 & DMX512 Applications

This PIC development board has been designed to develop RS485 based and DMX512 applications, the board has 28 pin SMD Pic micro-controller, RS485 chip for communications, all I/O line has pull-up resistor which can be soldered as per application requirement on particular port pins. In-circuit programming of PIC micro-controller can be achieved via a 6-pin header that is compatible with the Microchip PICkit2 or PICkit3. On board 3.3 V and 5V DC regulators allows using 3V and 5V PICS. This board support both 3.3V low power and normal 5V operation, supply selection with jumper closure. All I/O pins supported with parallel GND and VCC header connector for easy interface of any device or sensor and also can be used as address setting jumper by pulling high or low. Important  for DMX512 Address.

PIC Development Board for RS485 & DMX512 Applications – [Link]

8 Channel RS485 Relay Board

8-channel-rs485-driven-relay-board-img

This project helps you control 8 relays using RS485 link with the help of a PC. This kit can effectively convert  a standard PC to a powerful   PLC ( programmable logic controller ). At the PC end , you will need to use our RS232 to RS485 Interface – C020 or any other suitable RS232 to RS485 Converter.

The project can offer a low-cost serial relay contact interface, easy to use with Visual Basic, Basic, C, Labview, Testpoint, or other high level languages that allow access to a serial port.

You can simply use the accompanying software provided with this project or issue control commands using any popular Terminal Port software available on the net.

The Serial port on the computer should be configured to 2400 baud – 8 bit words – 1 stop bit – no parity

8 Channel RS485 Relay Board – [Link]

USB to RS485 converter

pcb-assembled

Marko Pavlin has published a USB to RS485 converter. He writes:

Testing of sensors with RS485 using PC without proper interface is not possible. Since RS232 interfaces are very rare, the interface should be hooked to USB. The interface between USB and RS485 can be soldered with one of the many FTDI interfaces with added RS485 driver, or bought as assembled module. There is always the third option. I made it from scratch.

USB to RS485 converter – [Link]

How to ensure a stabile RS485 communication?

obr1769_p808

LTM2881 allows RS485 or RS422 communication even in harsh environment.

RS485 is often used as physical layer for industrial buses like ModBus, ProfiBus, InterBus, P-Net, BACnet and Bit-Bus. Bus length depends on data rate and can reach as much as 1000m.

Correct function of RS485 transceiver requires return path between GND of particular transceivers. This path can be created by connecting GND to earth potential (earthing) or by additional wire. In practical RS485 systems, ground potentials vary widely from node to node, often exceeding the tolerable range. This can result in an interruption of communications or destruction of a transceiver. Standard RS485 transceiver LTC485 is fully functional if GND potential difference is within ±7V. If difference exceeds ±14V damage or destruction can occurs.Using of additional wire which connects together all transceivers GND may looks like a good way how to avoid potential differences. But this leads to creation of ground loops that can even worsen situation.

Optimal solution is to use galvanically isolated RS485 transceiver powered from galvanically isolated power supply. In such a way GND of transceiver is fully isolated from earth potential and additional wire can be used to connect all transmitters GND together without creation of dangerous earth loops.

LTM2881 integrates all necessary components for galvanically isolated RS485/RS422 interface including isolated DC/DC converter into one compact part. No external components are required. Isolation is rated to 2500VRMS/1min and 560Vpeak-peak for continuous operation.


How to ensure a stabile RS485 communication? – [Link]

RS232 To RS485 Module

C038_1

RS232 to RS485 Board (R) provides a seamless connection of the PC to an RS485 network.

  • Simplex connection of this interface to the RS485 network
  • Easy way of switching the modes between Receiver and Transmitter ( Slide Switch)
  • 5 V regulated supply provision on board
  • 9-pin, PCB mounted, Female type D-connector available
  • Supply can also be provided by the host interface via Header connector carrying data
  • Four mounting holes 3.2 mm each
  • PCB dimensions 82 mm x 33 mm

RS232 To RS485 Module – [Link]