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UniPi Neuron M403


UniPi Neuron M403 PLC features high number of relay outputs, offering 28× RO. The M403 is a smaller variant of the L403 model. 

Package contents:

  • UniPi Neuron M403 controller
  • removable screw connectors
  • DIN rail holder(35 mm)
  • power supply (optional)
  • microSD memory card (optional)
  • Mervis lifetime license

The product features an integrated Raspberry Pi 3 Model B computer

409,00 €
338,02 € excl. TAX
out of stock


  • 4× digital inputs 5-24 V DC
  • 4× digital outputs max. 750 mA at 50V DC
  • 28× relay output (max. voltage 250V AC/30V DC, max. switchable current 5A)
  • 1× analog output 0-10V
  • 1× analog input 0-10V DC/0-20mA, 4-20mA
  • 1× 1-Wire bus (galvanically isolated)
  • 1× RS485 (Modbus RTU protocol)
  • RTC (Real Time Clock) with backup for up to 7 days
  • 4× 1.2 GHz CPU, 1GB RAM
  • 4× USB 2.0
  • 1× 10/100Mbit Ethernet
  • 4 DIN module size (70×90×60 mm)
  • DIN rail mounting, anodized aluminium case (IP20)
  • 24V DC power supply required
  • microSD memory card required


The M403's I/O architecture is focused on a large number of relay outputs while retaining the basic digital I/O capability. That makes the unit suitable for larger projects focusing on switching two-state devices by alternating or direct voltage (boilers, water heaters etc.). The unit also serves as a smaller variant of the L403 unit.

Inputs & Outputs

Digital inputs (DI) are used for reading 5-40V DC voltage pulses generated by various binary devices such as digital lightning switches, motion sensors, digital measuring devices (energy meters, flow meters, pressure meters) etc. Digital outputs of the M403 model also feature an in-built pulse counter. 

Digital outputs (DOare using 5-50V DC voltage pulses at 750mA max. current for switching various two-state devices such as door locks, shutter controls, automatic doors, heat pumps, lights etc. Digital outputs of Neuron controllers also feature the PWM (Power Width Modulation) function, allowing the output to transmit analog signal via binary modulated signal. 

Relay outputs (RO) are using AC/DC voltage or current for switching two-state devices such as boilers, water heaters, electric motors or larger external relays. Neuron line relays are rated for max. 250V DC/30V AC voltage or max. 5A switchable current. 

Analog input (AI) reads 0-10V DC voltage signal or 0-20mA current signal. On the M403 model, analog input can be used for precise current or voltage measurement based on current AI register settings.,

Analog output (AO) serves for regulating and controlling of various devices (three-way valves, heat exchangers, circulation pumps etc.) by 0-10V voltage or 0-20mA current signal. Analog output on the M403 model allows the user to set output voltage or current through corresponding AO register settings. 

More detailed info about I/O usage and settings can be found in Neuron technical documentation (see Files tab above)

Communication interfaces

By standard, all Neuron-line controllers (except the Neuron 500 line) feature a single RS485 serial line for communication with external devices or connection of extension modules (such as Neuron xS series) using the Modbus RTU protocol. A single RS485 can communicate with up to 256 devices.

Included is also a single 10/100MBit Ethernet port for network communication and a single 1-Wire bus for connection of various 1-Wire sensors (such as digital thermometers). A single 1-Wire channel can communicate with up to 15 sensors at once. 

Other features

Due to 1GB RAM and a 1.2GHz quad-core CPU, all Neuron models possess a very low response rate (ie. delay between input signal reception and output response) of approximately 0.5 ms, giving them a high level of performance.

All components are encased within a durable anodized aluminium case providing IP20 cover. The unit's size is 8 DIN modules, DIN rail holder is included in the package. 

Possible use

  • Lightning control
  • Boiler control
  • Temperature measurement
  • Remote home control
  • Remote shutter control
  • Notification sending
  • Energy monitoring
  • Gateway for other systems
  • Irrigation systems
  • Building management systems
  • HVAC control and regulation
  • SCADA systems


Neuron is CE and EMC tested and is compliant with all corresponding European PLC standards. In accordance with these standards Neuron can be used in: 

  • Residential buildings, apartments
  • Commercial areas, offices, banks
  • Entertainment areas, cinemas, bars, pubs, dance clubs
  • Outdoor places, gas stations, parking lots, sport centers
  • Areas of light industry, workshops, laboratories, service centers

The EU declaration of conformity can be found in the Files tab (see above). 

Standard Neuron model overview

Model DI DO RO AI AO RS485 Common features
Type S (size on DIN rail: 4 modules = 7 cm)

4 × 1.2 GHz CPU
1-Wire bus (up to 15 sensors per channel)
10/100Mbit Ethernet
Wi-Fi + Bluetooth

S103 4 4 - 1 1 1
S103-G* 4 4 - 1 1 1
S103-IQRF** 4 4 - 1 1 1
Type M (size on DIN rail: 8 modules = 14 cm)
M103 12 4 8 1 1 1
M203 20 4 14 1 1 1
M303 34 4 - 1 1 1
M403 4 4 28 1 1 1
M503 10 4 5 5 5 2
Type L (size on DIN rail: 12 modules = 21 cm)
L203 36 4 28 1 1 1
L303 64 4 - 1 1 1
L403 4 4 56 1 1 1
L503 24 4 19 5 5 2
L513 16 4 10 9 9 3

Extension modules (size on DIN rail: 4 modules = 7 cm)

xS10 16 - 8 - - 1

Extension modules communicate over Modbus. It is possible to connect them to the control unit via RS485 interface. Extension modules are compatible with any control unit with the RS485 interface and Modbus support.

xS30 24 - - - - 1
xS40 8 - 14 - - 1
xS50 6 - 5 4 4 1

* features an integrated wireless GPRS module.
** features an integrated TR-76D smart IQRF transciever

Further info


Technological specification of the product
Guide to set up and use this device, technological documentation
Modbus register map
Table overview of Modbus registers
Declaration of conformity
Instruction leaflet
Regulatory Compliance and safety information added to each unit

CPU 4 × 1 GHz
USB 2.0 4
Ethernet 10/100 BaseT
Digital inputs 4
Transistor outputs 4
Analog inputs 1
Analog outputs 1
Dimensions 140 mm × 90 mm × 60 mm
Relay outputs 28
RS485 interface Yes
1-Wire bus Yes (with galvanic isolation)
Weigth 800 g
Mounting DIN (35 mm)
Power 24 V DC
RTC backup maximum 7 days