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UniPi Neuron M503


UniPi Neuron M503 PLC represents a basic model of the Neuron 500 line, focused on an increased number of analog I/O. The M503 also features an additional RS485 serial line and is a smaller variant of the L503 model 

Package contents:

  • UniPi Neuron M503 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
Less than 5 items in stock


  • 10× digital inputs 5-24 V DC
  • 4× digital outputs max. 750 mA at 50V DC
  • 5× relay output (max. voltage 250V AC/30V DC, max. switchable current 5A)
  • 5× analog output 0-10V
  • 5× analog input 0-10V DC/0-20mA, 4-20mA
  • 1× 1-Wire bus (galvanically isolated)
  • 2× 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 M503 is a smallest model of the 500 line (consisting of the M503, L503 and L513 models) and as the rest of the 500 line, it features multiple analog I/O modules and additional RS485 universal bus port while retaining a set of digital and relay I/O capability. The M503 represents a smaller variant of the L503 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 inputs are operating with either 0-10V voltage or 0-20mA current signal for receiving data from corresponding sensors (such as resistance thermometers). The M503 (as well as other Neuron 500 controllers) is provided with two types of analog inputs. Group 1 analog input (AI1.1) does not feature the option to read data from resistance sensors, it can be however used for voltage or current measurement based on AI register settings. Group 2 analog inputs (AI2.1-AI2.4) then allow the user to perform a precise measurements of voltage, current or resistance based on current output register settings. 

  • voltage measurement 0-10 V (16bit resolution)
  • voltage measurement 0-2.5 V (24bit resolution)
  • current measurement 0-20 mA (16bit resolution)
  • resistance measurement (from PT100, PT1000 or NTC sensors) using three-wire (three conductors, 0-100 Ω, 24bit resolution) or two-wire (two conductors, 0-1960 Ω, 24bit resolution) wiring method.

Analog outputs 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. Group 1 analog output of the M503 (AO1.1) allows the user to set output voltage through corresponding AO register settings. This setting is performed by inserting 0-4000 value (equal to 0-10V voltage range) into the AO register.

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

Communication interfaces

In contrast to other Neuron models, the M503 features two RS485 serial lines for communication with external devices or for extension modules connection (such as the Neuron xS extension module line). Single RS485 line can communicate with up to 256 devices, the M503 can thus communicate with up to 512 devices, using two different communication protocols. 

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 eloxed aluminium case providing IP20 cover. The unit's size is 12 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

CPU 4 × 1 GHz
USB 2.0 4
Ethernet 10/100 BaseT
Digital inputs 10
Transistor outputs 4
Analog inputs 5
Analog outputs 5
Dimensions 140 mm × 90 mm × 60 mm
Relay outputs 5
RS485 interface 2 ×
1-Wire bus Yes (galvanically isolated)
Weigth 750 g
Mounting DIN (35 mm)
Power 24 V DC
RTC backup maximum 7 days