Solidot MT4 – Support, Wiring Diagram & Commissioning

The MT4 brings inputs and outputs straight onto Ethernet: Modbus TCP, two RJ45 sockets with a built-in switch, spring-cage terminals. This guide applies to all MT4 models in the Shop – digital with 16 or 32 channels, analog with four or eight channels, and the mixed MT4-88B40I. It takes you from snapping the module onto the DIN rail to the first signal in your controller: power supply, wiring, setting the IP address, creating the registers in the master.

1. 1Mount on the DIN railRequired

   The module measures 25 × 102 × 72 mm (W × H × D) and snaps onto a 35 mm DIN rail. It must sit vertically so that air can flow through the housing.

   Minimum clearances according to the manual: 10 mm to neighbouring modules, 45 mm above and 25 mm below to other devices or cable ducts. Do not mount next to or above devices that give off a lot of heat.

   Mounting

   1. Pull the latch at the bottom of the module outwards until it audibly clicks into place.

   2. Hook the top edge of the mounting clip onto the top edge of the DIN rail and swing the module onto the rail.

   3. Push the latch towards the rail until it clicks – the module is now secure.

   4. Removal: insert a flat-blade screwdriver into the latch, lever it towards the module (it clicks) and remove the module in reverse order.

   Source: Manual chap. 1.2, 3.1, 5, 5.1, 5.2

2. 2Connect system and field supplyRequired

   The system supply powers the electronics: 24 V DC (18–30 V) to the three-pole terminal on the top, assigned 24V, 0V and PE. The manual recommends a twisted cable.

   The field supply powers the inputs and outputs and goes to terminals 24V/0V in the terminal block (terminal 9/10 and 19/20, each pair connected internally). Modules with two blocks (32 channels, 16 DI/16 DO) need it on both blocks, because the blocks are not connected internally. Loads on outputs run from the same field supply as their block.

   Analog inputs and voltage outputs have no field terminals. The current outputs (MT4-A04I, MT4-A08I) need 24 V at terminal 9/10 or 19/20.

   Terminals

   Terminal	Cross-section	Note
   Supply, 3-pole	0.3–1.5 mm² (22–16 AWG)	24V, 0V, PE
   Signal terminals, 2 × 20-pole	0.3–1.0 mm² (22–17 AWG)	Spring-cage, screwless

   The manual does not state the current consumption of the electronics or the permissible current per field terminal. The cross-sections in the wiring diagram are derived from this and marked as such.

   After switching on, PWR lights up green.

   Show wiring “System supply 24 V”Show wiring “Field supply 24 V”

   Source: Manual chap. 3.1, 6.1, 6.2, wiring diagrams chap. 6.3; MT4-88B40I chap. 5.3

3. 3Wire inputs and outputsRequired

   Strip 10 mm of insulation. Insert solid wires directly; use a wire ferrule for fine-stranded wires (length 10 mm, e.g. E0510 for 0.5 mm²). Press the button above the terminal with a flat-blade screwdriver up to 3 mm wide.

   Digital inputs are PNP: the sensor applies +24 V to the input (“1” from 15 V). Digital outputs are PNP with max. 500 mA per channel and switch +24 V to the load.

   Each analog channel has one signal connection (AI0 … or AO0 …, terminal 1–8) and COM next to it (terminal 11–18). All COM are connected internally; all channels must be referenced to the same source. Use twisted, shielded pairs for analog signals.

   Connecting analog transmitters (wiring diagrams chap. 6.3)

   Type	Signal to	COM to
   4-wire, own supply	Signal + to AI	Signal −
   3-wire	Signal output to AI	0 V of transmitter and power supply
   2-wire 4–20 mA	Loop (−) to AI, + to +24 V	0 V of the power supply

   On the current module, 2 V drop across the input at 20 mA (100 Ω, calculated). A 2-wire transmitter needs this voltage in addition to its minimum voltage.

   Each channel has a green LED: it lights up as long as a signal is present at or output by the channel.

   Show wiring “PNP sensors on DI”Show wiring “Valve and lamp on DO”Show wiring “Transmitter 4-wire”Show wiring “3-wire transmitter”Show wiring “2-wire transmitter 4–20 mA”Show wiring “Setpoint to frequency inverter”

   Source: Manual chap. 3.2, 3.3, 4.2, 6.1, 6.2, 6.3

4. 4Connect the PC and check the connectionRequired

   From the factory, every module has the IP address 192.168.1.120, mask 255.255.255.0, gateway 192.168.1.1. For your PC to reach it, set the network adapter to a free address in the same network, e.g. 192.168.1.10.

   Check the connection

   1. Connect the PC to one of the two RJ45 sockets with a patch cable.

   2. On the PC, set the address 192.168.1.10 and the mask 255.255.255.0 (example, the address is freely chosen).

   3. Open the command prompt and enter ping 192.168.1.120.

   4. Replies without packet loss: the connection is up. Otherwise check the cable, the addresses and the LEDs at the socket (green = link, orange flashing = data traffic).

   Show wiring “PC for setup”

   Factory IP and addresses in the Modbus & IP tab

   Source: Manual chap. 4.2, 7.1

5. 5Set the IP addressRequired

   Each module needs its own address in your plant network. You set it on the module's web page.

   Assign a new address

   1. Open http://192.168.1.120 in the browser.

   2. Enter the new IP address, subnet mask and gateway.

   3. Click Save and restart the module.

   4. Switch the PC to the new network and check the new address with ping.

   5. Connect the next module and change it the same way.

   Write the new address on the module, e.g. with a label. If it is forgotten, the factory default helps (step “Troubleshooting and reset”).

   Factory IP and addresses in the Modbus & IP tab

   Source: Manual chap. 7.1

6. 6Set up in the Modbus TCP masterRequired

   The MT4 is a Modbus TCP slave. In your controller (PLC, HMI or PC), set it up with its IP address, port 502 and unit ID 1 (values from the CODESYS example in the manual). Function codes 1, 2, 3, 15 and 16 are supported.

   Each channel has a fixed address. Which notation your software expects – 40001, 400001 or area + number such as 4x 1 with Kinco – you select in the Modbus & IP tab; it lists all channels of your model.

   All channel addresses for your model, terminal by terminal, are in the Modbus & IP tab.

   Address areas (counting from 1, Modbus standard)

   Data	Range	Addresses	Function code
   Digital inputs X00 …	1x Discrete Inputs	ab 10001	02
   Digital outputs Y00 …	0x Coils	ab 00065	15, read back 01
   Analog inputs AI0 …	4x Holding Register	ab 40009	03
   Analog outputs AO0 …	4x Holding Register	ab 40017	16
   Measuring range per channel	4x Holding Register	ab 40033	16

   If your software counts from 0, each address is one lower (40008 instead of 40009). Some programs use six digits: 400009.

   The MT4 only knows function codes 01, 02, 03, 15 and 16. For single outputs, select “Write Multiple” (FC 15/16) in the master.

   The assignment X00 = first input and Y00 = coil 65 (protocol address 64) is derived from the address table in the manual.

   Show wiring “Modbus TCP to the master”

   Show addresses for my model

   Source: Manual chap. 7.4, 7.5; MT4-88B40I chap. 6.4

7. 7Example: CODESYS V3.5Optional

   The manual shows the integration into CODESYS V3.5 step by step. Here it is in short form.

   Set up the MT4 in CODESYS

   1. Create a new project. Under “Device”, add an Ethernet adapter with Add Device and select the network adapter in the same network as the module.

   2. Under the Ethernet adapter, add a “Modbus TCP Master”, and below it a “Modbus TCP Slave”.

   3. In the slave under “General”, enter the IP address of the module, unit ID 1, response timeout 1000 ms and port 502.

   4. Under “Modbus Slave Channel”, create the channels with “Add Channel”, e.g. function code 3, offset 0 for the inputs and function code 15, offset 64, length 16 for the outputs.

   5. Analog inputs: function code 3, offset 8, length 8; plus function code 16, offset 32, length 8 for the measuring ranges.

   6. Log in, start and watch or write the values under “ModbusTCPSlave I/O Mapping”.

   Source: Manual chap. 7.5

8. 8Select the measuring range of the analog channelsOptional

   Each analog channel has its own measuring range. You set it via a register (32 + channel, function code 16) or on the module's web page. The code also determines which number range appears in the measured value register.

   Range codes

   Code	Current (…I)	Voltage (…V)
   0	4–20 mA → 0–65535	±10 V → −32768–32767
   1	0–20 mA → 0–65535	0–10 V → 0–65535
   2	4–20 mA → 0–27648	±10 V → −27648–27648
   3	0–20 mA → 0–27648	±5 V → −27648–27648
   4	–	1–5 V → 0–27648
   5	–	2–10 V → 0–27648

   Example (calculated, linear): code 2, transmitter 4–20 mA, 12 mA at the input → 13824 in the register (middle of 0–27648).

   Codes 2 to 5 use the range 0–27648, which many controllers know as the nominal analog range. The manual does not state the factory default – so always set the range explicitly.

   Resolution 16 bit, accuracy ±0.1 %, sampling up to 1 kS/s.

   Show wiring “Transmitter 4-wire”Show wiring “Setpoint to frequency inverter”

   Source: Manual chap. 2.2, 3.3, 7.3.2, 7.4

9. 9Outputs on loss of connectionRequired

   If the connection to the master is lost, the Clear/Keep setting on the web page determines what happens to the outputs. From the factory, the switch-off time is 0, so the function is off.

   For valves, drives and anything that must not keep running uncontrolled: enter Clear/Keep = 0 and a switch-off time of 1–30 s. The module then switches the outputs off after this time. With Clear/Keep = 1, the outputs hold their last state.

   Parameter	Value	Meaning
   Clear/Keep	0	Switch outputs off after the time has elapsed (factory default)
   Clear/Keep	1	Outputs hold the state before the loss of connection
   Switch-off time	1–30 s	0 = function off (factory default)

   Applies to all modules with outputs, digital and analog. The manual describes the setting in Internet Explorer; a current browser shows the same web page.

   Show wiring “Valve and lamp on DO”

   Source: Manual chap. 7.3.1; MT4-88B40I chap. 6.3.1

10. 10Connect further modules in a lineOptional

    Thanks to the built-in switch, you connect several MT4 without an external switch: ETH2 of one module to ETH1 of the next. Up to 127 stations are possible, max. 100 m per segment.

    Patch cable category 5 or higher, double shielded (braid and foil), is recommended.

    Each module in the line needs its own IP address (step “Set the IP address”).

    If a module in the line has no power, you can no longer reach the modules behind it (derived from the built-in switch; the manual does not mention a bypass).

    Show wiring “Further module in daisy chain”

    Solidot patch cable 0.5 mSolidot patch cable 1 m

    Source: Manual chap. 1.1, 3.1, 6.2

11. 11Troubleshooting and resetRequired

    Restore the factory IP

    1. Leave the module switched on.

    2. Press the reset button for 1 s, using an insulated tool less than 1.2 mm in diameter or thickness.

    3. RUN/ERR flash and then light up steadily.

    4. Switch the module off and on again. It can now be reached again at 192.168.1.120.

    • PWR lights green: system supply OK.
    • RUN lights green: the module is working and communicating.
    • ERR is off.
    • LED at the socket green, orange flashing: link with data traffic.
    • Input LED lights up when the sensor switches; the master reads the channel.
    • The master can switch the output, the load has its field supply.
    • Clear/Keep and switch-off time are set.

    LEDs

    LED	State	Meaning
    PWR (green)	off	no supply or faulty supply
    RUN (green)	off	Operating fault, e.g. communication timeout
    ERR (red)	flashing	Module fault, e.g. setting out of range or communication error
    Socket 1/2 green	off	no network connection
    Socket 1/2 orange	off	no data exchange
    Channel 0–F (green)	off	no signal at the channel or signal faulty

    Resetting restores the IP settings to factory default (192.168.1.120, mask 255.255.255.0, gateway 192.168.1.1).

    Source: Manual chap. 4.2, 7.2

Revision 1.0 · 01.10.2026 · Source: MT4 Series Integrated I/O User Manual V1.16 (12/2025); MT4-88B40I user manual (2025). The manufacturer manual and applicable standards take precedence; installation and commissioning by a qualified electrician only.

Mounting step by step

1. 1Choose the installation site

   Protection class IP20: the module belongs in a control cabinet or an enclosure. The cabinet needs good ventilation, e.g. a fan.

   Mount the module vertically so that air flows through the housing. Do not mount it next to or above devices that give off a lot of heat. Operating temperature 0–55 °C, humidity up to 95 %, non-condensing.

   At least 10 mm to neighbouring modules, 45 mm upwards and 25 mm downwards to devices or cable ducts. This leaves room at the top for the supply connector and patch cables.

   Show clearances in the drawing

2. 2Mounting and removing

   Mount and remove only with the power off.

   • Pull the latch at the bottom of the module outwards until it clicks into place.

   • Hook the module onto the top of the DIN rail and swing it onto the rail.

   • Push the latch towards the rail until it clicks.

   • Removing: insert a flat-blade screwdriver into the latch, lever it towards the module and swing the module off.

   Show wiring “System supply 24 V”

3. 3Connecting the wires

   Strip 10 mm of the wire. Stranded wires get a wire ferrule with a 10 mm sleeve length; solid wires go in directly.

   Press down the push button above the terminal with a flat-blade screwdriver (up to 3 mm), insert the wire, release, give the wire a short pull.

   Signal terminals take 0.3–1.0 mm², the supply terminal 0.3–1.5 mm². Run the supply cable twisted, use shielded pairs for analog signals.

   Show wiring “System supply 24 V”Show wiring “PNP sensors on DI”

Revision 2.0 · 01.10.2026 · Source: MT4 Series Integrated I/O User Manual V1.16 (12/2025), ch. 5; Solidot 3D models EC4_PN4_MT4_1/_2 V1.00. The manufacturer manual and applicable standards take precedence; installation by a qualified electrician only.