Home automation electronics and SW development - Ing. Pavel Sedláček - Arduino
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New Railduino 2.0 should have
12x relays 5A
8x relays 5A + 4x relays 7A
4x SSR 2A + 4x relays 5A + 4x relays 7A
8x SSR 2A + 4x relays 7A
12x SSR 2A
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Homepage > Railduino module > Basic settings and connections

Basic settings and connections

Since March 2017 there will be new FW for Railduino 1.3 available - plain RS485 and UDP packets support !!!

Pic. 1 – The block diagram of use of the digital inputs / relay outputs of Railduino Module
 for reading of button and for 230V AC outlet socket control
via RS485 bus (485 or Modbus RTU) or LAN (UDP packets or Modbus TCP).

pic. 2 – The block diagram of use of the PWM outputs of Railduino Module
for control of coloured LED strip lights via RS485 bus (plain 485 or Modbus RTU).

pic. 3 – The block diagram of the DS18B20 temperature sensors
connected to 1 wire bus of Railduino Module and connection to LAN (UDP packets or Modbus TCP).

pic. 4 – The block diagram of use of Railduino Module analogue inputs
for water level status reading with ultrasonic sensor and connection to the RS485 bus  (plain 485 or Modbus RTU).

UDP / RS485 / Modbus communication settings
Railduino module needs to be communicated with the following settings:
485 or Modbus RTU - serial link RS485:

  • Communication speed                    115200 Bd
  • Number of data bites                        8
  • Number of stopbites                         1
  • Parity                                              no
UDP or Modbus TCP - Ethernet

  • Modbus TCP port                             502
  • UDP receiving port                           55555
  • UDP outgoing port                            44444
  • IP address
    • dynamic - Modbus TCP
    • static - UDP packets

Modbus RTU or TCP supported functions:
  • FC16     - entry into the holding regisers
  • FC3       - reading from the holding registers

UDP syntax:
  • signals:
    • DS18B20 1wire sensor packet:    rail1 1w 2864fc3008082 25.44
    • DS2438 1wire sensor packet:     rail1 1w 2612c3102004f 25.44 1.23 0.12
    • digital input connected:        rail1 di1 1
    • digital input disconnected:     rail1 di1 0
    • analog input state:             rail1 ai1 520
  • commands:
    • relay on command:               rail1 do12 on
    • relay off command:              rail1 do5 off
    • pwm output command:             rail1 pwm1 255

RS485 syntax must have n symbol at the end of the command line
The address of the Railduino module is set up with DIP switch. Since it is a 4-pole-switch, it is possible to set up to 16 various addresses. The initial module address is set to1.
In case of Modbus TCP option LAN connection uses DHCP server IP address  assignment – the address is necessary to find out e.g. in a router with DHCP server function. Each Railduino Module in the variant with Ethernet connection has got its own MAC address.

In case of UDP packets option LAN connection uses static IP address. Each Railduino module has its own IP address according to DIP switch settings.
If the longer RS485 bus between Railduino modules is used, for more reliable communication it is sufficient to connect so called bus terminator or terminating resistor. This is possible with the jumper placed next to DIP switch for the address setting.
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