WB-MRPS6 Modbus Relay Module

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This page is a translated version of the page WB-MRPS6 Modbus Relay Module and the translation is 100% complete.
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WB-MRPS6 six-channel relay modules are designed for industrial and home automation systems. Modules, depending on the modification, are designed for switching the power load of General purpose, including inductive and capacitive: control of led lamps, incandescent lamps, pulse power supplies; for use in PDU, etc.

The modules are designed for a maximum current of 16A (rated load 10A) and can be used without intermediate contactors.


The module is available in two versions (S) and (P), the difference between which is the maximum allowable switching current.

The naming scheme:

WB-MRPS6 Relay output type
S ultra-high starting current (relay with additional tungsten contacts)
P a high inrush current

Technical specifications

Our detailed article in russian on habr.com about the choice of relay parameters for the switched load: https://habr.com/ru/company/wirenboard/blog/422197/
Parameter Value
Supply voltage 9 — 24 V DC
Power consumption
  • Idle mode (all relays switched off) — 0.5 W
  • All relays included: 3W
  • Peak value — up to 8 W for 20 ms
"'Terminals and wire section'"
Recommended wire cross-section with NSUI, mm2 0,75 — 1 for control inputs, the 2.5 for power input
Length of the standard sleeve NSVE, mm 8
Torque of screws, N∙m 0,2 for control inputs , 0,5 — for power inputs
Output type Mechanical relay contacts
Output configuration 6 outputs that are connected to the relay contacts
Configuration of each output contacts Two-position, normally open (COM and NO)
Maximum switching voltage, AC 250 V
Maximum switching voltage, DC 30 Volts
Maximum switching current per channel

see table in #Relay parameters

Contact resistance < 100 milliohms
Voltage isolation between the controller and the output 1500 V (RMS value)
Term life: see table in #relay Parameters
Management interface RS-485
Interface isolation Uninsulated
Communication protocol Modbus RTU, the address is set by software, factory settings are indicated on the label
RS-485 interface parameters set programmatically (see register Card);
default: speed — 9600 bit/s; data — 8 bit; parity bit — none (N); stop bits — 2
Ready for operation after power supply ~0.03 c
Width, DIN units 3
Overall dimensions (l x W x h) 53.3 x 90.2 x 57.5 mm
Power and data exchange indication Green status led
Relay channel status indication Orange LEDs, 1 — 6
operating Conditions
Air temperature
Relative humidity Up to 92%, no condensation

Module dimensions

overall dimensions of the modules make up 53,3 x 90,2 x 57,5 mm (l x W x h)


Modification S Modification P
Maximum switching current,

resistive load 230V AC

Maximum switching current,

resistive load 30V DC

- -
Maximum switching power

for incandescent lamps (230V AC)

"'3000W"' 1000W
Maximum allowable inrush current

(within 20ms, for no contact)

"'165A"' "'80A"'
Maximum allowable inrush current

(within 200 µs, for no contact)

"'800A"' -
Contact resistance 100 milliohms ?
Contact material "'W+AgSnO2"' AgSnO
Contact configuration SPST (NO, COM)
Lifetime: number of switches

for load 16A 230V AC, cos φ = 1

12 000 50 000
Lifetime: number of switches

without load

5 000 000 30 000 000
Relay model Hongfa HF115F-S TE Connectivity RT33L
Peculiar properties Very high starting current High starting current
Application General purpose power load, inductive load,

capacitive load. Motors, contactors, incandescent lamps,

LED lights, switching power supplies, etc.

General purpose power load, inductive load,

capacitive load. Motors, contactors, incandescent lamps,

switching power supplies, etc.


Model WB-MRPS6 is not equipped with discrete inputs.

Installation of modules

The relay module is mounted on a standard 35 mm wide DIN rail and occupies the width of 3 DIN modules.

Terminal blocks with 3.5 mm increments on the relay board are used to connect power and control lines (RS-485). The cross-section of wires connected to the screw terminals of the relay outputs must correspond to the power of the switched load: it is important not to exceed the recommended current — 16 A.

If the device is the last one on the RS-485 line, a 120 Ohm resistor-terminator must be installed between its inputs A and B. Practice shows that in case of bench tests with a small length of the RS-485 line and a small number of devices, terminator for the last device in the line is not necessary.

The module must be installed in such a way as to meet the requirements of electrical safety and to prevent accidental contact of contacts under high voltage. The module must be operated under recommended environmental conditions.

Sample of WB-MRPS6 module installation and connection.

Relay operation in case of power failure

Depending on the value written to the storage register 0x06, after the power is turned off and restored, the relays will remain off (if the value is 0, or turn on those that were turned on before the power interruption if the register has a value of 1). This feature appeared in the modules with the firmware, starting with version 1.5.3.

Modbus Control

Details of the work with the module via Modbus Protocol is written in Relay Modules Modbus Management . There you can also find a map of the device registers.

Back to peripheral devices list

Device firmware update

Starting with the new firmware versions of the device, the firmware update functionality (firmware) via the Modbus Protocol is supported. This makes it possible to extend the functionality of the devices and eliminate errors in the firmware directly at the installation site. Read more about flashing devices described in the article Download firmware to Wiren Board devices. A list of firmware versions that support the update, as well as devices for which this feature is implemented, can be found in Firmware Changelog.

Known faults and bugs

List of known faults

Images and drawings of the device

По ссылкам ниже вы можете скачать изображения и чертежи устройства WB-MRPS6/P.

Corel Draw 2018: WB-MRPS6_P.cdr.zip

Corel Draw PDF: WB-MRPS6_P.cdr.pdf

Autocad 2013 DXF: WB-MRPS6_P.dxf.zip

Autocad PDF: WB-MRPS6_P.pdf

По ссылкам ниже вы можете скачать изображения и чертежи устройства WB-MRPS6/S.

Corel Draw 2018: WB-MRPS6_S.cdr.zip

Corel Draw PDF: WB-MRPS6_S.cdr.pdf

Autocad 2013 DXF: WB-MRPS6_S.dxf.zip

Autocad PDF: WB-MRPS6_S.pdf