The Sfar MOD-1TE is a single-channel temperature input module manufactured by Aspar s.c. (Chwaszczyno, Poland) and sold under the SFAR brand (Solutions for Automation and Robotics). It accepts Pt100, Pt500 and Pt1000 RTDs (in 2-wire or 3-wire configuration), Ni100, KTY81-110, NTC Carel and all common thermocouple types (J, K, T, N, S, R, B), and exposes the measured value on Modbus RTU at register 30053 (A:51) as °C × 10.
The module is RS-485 only, so an external Modbus RTU-to-TCP gateway (e.g. SFAR-S-ETH, USR-W630, Waveshare RS485-to-Ethernet) is required for TapHome — the template uses an IpAddress import parameter and reaches the module through that gateway.
Hardware connection
Module overview
The MOD-1TE is a 90 × 56 × 17 mm DIN-rail module (DIN EN 50022, IP40, -10 °C to +50 °C, PC/ABS housing). It carries one temperature input (TI), one digital alarm output (DO), an RS-485 port, a power input and a Mini USB type B configuration port on the front.
| Indicator | Meaning |
|---|---|
| ON | Module is correctly powered |
| TX | Module replied to a valid Modbus request |
| IN | A sensor is connected on the temperature input |
| DO | Digital output is active (alarm asserted) |
Power supply
The module is powered through a 2-pin screw connector, accepting either DC or AC:
- DC: 10–38 V DC (typical 24 V DC, ~1 W consumption at 24 V)
- AC: 20–28 V AC (typical 24 V AC, ~2 VA at 24 V AC)
RS-485 wiring
The RS-485 bus uses a 3-pin screw terminal — A+, B- and GND — and must be wired with a shielded twisted pair (A/B on the pair, GND on the third conductor or shield).
Bus termination is mandatory. Place a 120 Ω resistor across A/B at both physical ends of the RS-485 segment. Up to 128 modules can share a single RS-485 segment.
The RS-485, power supply and measuring inputs are galvanically isolated from each other (1 kV). For best EMC behaviour, ground the cable shield at one end only and keep RS-485 cabling away from contactors, motor drives and switching power supplies.
Temperature input wiring
The temperature input uses a 3-pin screw terminal and supports several wiring schemes depending on the chosen sensor type. The same physical input is used for all sensor types — only the wiring and the InputSettingsRegister value change.
- RTD 2-wire (Pt100 / Pt500 / Pt1000): Sensor on
INAandCOM, with a jumper betweenINBandCOM. Lead-wire resistance must be compensated via register 40065. - RTD 3-wire (Pt100 / Pt500 / Pt1000): Sensor connected with three conductors to
INA,INBandCOM. No lead-wire compensation needed — the third wire is used to cancel cable resistance. - Thermocouple (J / K / T / N / S / R / B): Two-wire connection on
INA(positive) andINB(negative). Cold-junction compensation is performed automatically inside the module. - NTC Carel: Two-wire connection with a 7.5 kΩ ±1 % resistor in parallel with the sensor.
Digital alarm output (optional)
The module has one configurable digital output (250 mA / 50 V max), selectable as PNP or NPN, that can be used as a stand-alone thermostat output (cooling / heating with hysteresis). It is not exposed by the TapHome template — wiring it is optional.
Configuration
Default Modbus settings
Out of the box, the MOD-1TE communicates with the following parameters (must be matched on the gateway / TapHome side):
| Parameter | Default value |
|---|---|
| Slave address | 1 |
| Baud rate | 19200 |
| Data bits | 8 |
| Parity | None |
| Stop bits | 1 |
| Modbus mode | RTU |
| Reply delay | 0 ms |
All of these are configurable — slave address 1–247 and baud rate up to 115200. Configuration is done over the front-panel Mini USB type B port using the free Modbus Configurator software (download, no drivers required), or by writing the holding registers below over Modbus while the module is online:
| Register | Name | Values |
|---|---|---|
| 40003 | Baud rate | 0=2400, 1=4800, 2=9600, 3=19200 (default), 4=38400, 5=57600, 6=115200 |
| 40004 | Stop bits / Data bits | LSB: 1=1 stop, 2=2 stops · MSB: 7=7 data, 8=8 data |
| 40005 | Parity | 0=none (default), 1=odd, 2=even, 3=mark, 4=space |
| 40006 | Response delay | Time in ms |
| 40007 | Modbus mode | 0=RTU (default), 1=ASCII |
Slave addresses must be unique per RS-485 segment. If two modules with the same address share a bus, both will reply at the same time and you will see CRC / framing errors on the gateway.
Selecting the sensor type — InputSettingsRegister
The TapHome template’s InputSettingsRegister import parameter is — despite the name — the sensor-type code value that gets written into manufacturer register 40061 (“Input settings”) on init via:
MODBUSWNE(H, 61, Int16, $[InputSettingsRegister])Pick the value that matches the physical sensor wired on the temperature input:
| Code | Sensor type |
|---|---|
| 0 | Input disabled |
| 1 | Voltage 0–2048 mV |
| 2 | Voltage 0–256 mV |
| 3 | Thermocouple type J |
| 4 | Thermocouple type K |
| 5 | Thermocouple type T |
| 6 | Thermocouple type N |
| 7 | Thermocouple type S |
| 8 | Thermocouple type R |
| 9 | Thermocouple type B |
| 10 | Pt100 3-wire |
| 11 | Pt100 2-wire |
| 12 | Resistance 0–8 kΩ |
| 13 | Ni100 |
| 14 | KTY81-110 |
| 15 | Pt500 3-wire |
| 16 | Pt500 2-wire |
| 17 | Pt1000 3-wire |
| 18 | Pt1000 2-wire (template default) |
| 19 | NTC Carel (with 7.5 kΩ 1 % parallel resistor) |
Sensor measuring ranges (reference, from datasheet):
| Sensor | Operating range |
|---|---|
| Pt100 / Pt500 / Pt1000 | -200 °C … +850 °C |
| Ni100 | -60 °C … +180 °C |
| KTY81-110 | -55 °C … +150 °C |
| Type J thermocouple | -200 °C … +1200 °C |
| Type K thermocouple | -200 °C … +1300 °C |
| Type T thermocouple | -200 °C … +400 °C |
| Type N thermocouple | -200 °C … +1300 °C |
| Type S / R thermocouple | 0 °C … +1700 °C |
| Type B thermocouple | 0 °C … +1800 °C |
| Resolution / accuracy | 0.1 °C / ±0.5 °C |
For voltage (codes 1–2) and resistance (code 12) modes the same register 30053 is read but with different scaling (mV × 10 / mV × 100 / Ω). The TapHome template assumes a temperature sensor (°C × 10) and applies the
/10formula automatically — using a non-temperature sensor type is out of scope for this template.
Enabling Modbus communication via the gateway
Because the MOD-1TE has no native Ethernet, the module is reached through an external Modbus RTU-to-TCP gateway. Typical setup:
- Wire the module’s A+ / B- / GND to the gateway’s RS-485 port. Add a 120 Ω termination resistor at the far end of the bus.
- Power the gateway and the MOD-1TE.
- In the gateway’s web interface, set the serial side to match the module: 19200 baud, 8 data bits, no parity, 1 stop bit, RTU mode. Disable any “modbus poll / address translation” features — TapHome talks raw Modbus TCP.
- Set a static IP for the gateway (or DHCP reservation on the router) so TapHome can reach it reliably.
- In TapHome service settings, import the
Sfar MOD-1TEtemplate and fill in:- IpAddress — IP of the gateway
- SlaveId — Modbus address of the module (default
1) - InputSettingsRegister — sensor-type code from the table above (default
18= Pt1000 2-wire)
Module variables
| Variable | Default | Description |
|---|---|---|
IpAddress | 192.168.0.1 | IPv4 address of the Modbus RTU-to-TCP gateway. |
SlaveId | 1 | Modbus slave address of the module on the RS-485 segment (1–247). Must be unique per segment. |
InputSettingsRegister | 18 | Sensor-type code written to register 40061 on init. Despite the name, this is a value, not a register address. Use the table above to pick the correct code for your physical sensor. |
Device capabilities
Temperature reading
The template exposes a single device — Temperature Sensor — that reads register A:51 (manufacturer register 30053, “Temperature”) as a signed 16-bit integer and divides by 10 to obtain the value in °C. The sensor type is configured at install time through the InputSettingsRegister parameter (default 18 = Pt1000 2-wire), and the module then handles RTD linearisation, lead compensation (3-wire), thermocouple linearisation and cold-junction compensation internally.
| |
Because every MOD-1TE template instance covers exactly one sensor, install one TapHome module per physical MOD-1TE on the bus and set
SlaveIdaccordingly (e.g. 1, 2, 3 …). All modules can share a single RS-485 segment and a single RTU-to-TCP gateway.
Troubleshooting
No temperature value (device offline in TapHome)
- Check the ON LED on the module — if it is off, verify the 24 V DC / 24 V AC supply on the power terminal.
- Check the TX LED while TapHome is polling — it should blink on every successful request. If TX never lights up:
- Verify
IpAddressmatches the gateway and that the gateway is reachable (ping). - Verify the gateway’s serial settings: 19200 / 8N1 / RTU.
- Verify
SlaveIdmatches the address actually configured on the module (default1). - Swap A and B — many gateways label them in reverse.
- Check that GND is connected between the module and the gateway. Without GND, the receiver bias may sit outside the valid common-mode range.
- Verify
- Verify there is exactly one 120 Ω termination resistor at each end of the RS-485 segment — neither more nor fewer.
Reading is stuck at 0, -200 °C or some extreme value
- Check the IN LED — if it is off, the sensor is not detected on the input. Inspect the wiring on the temperature input terminal:
- RTD 2-wire: jumper between INB and COM is required.
- RTD 3-wire: all three conductors must be in place.
- Thermocouple: polarity matters (positive on INA, negative on INB).
- NTC Carel: 7.5 kΩ ±1 % parallel resistor must be present.
- Verify
InputSettingsRegistermatches the physical sensor — a Pt100 wired but the parameter set to18(Pt1000 2-wire) will produce wildly wrong values. - For 2-wire RTDs over long cable runs, configure lead-wire resistance compensation in register 40065 using the Modbus Configurator (or accept the offset).
Two modules respond at the same time / random CRC errors
Two devices share the same SlaveId on the RS-485 segment. Disconnect modules one by one and use the Modbus Configurator over Mini USB to set unique addresses (1–247).
Changing baud rate or parity
If you changed baud rate / parity via register 40003 / 40005 over Modbus and lost communication afterwards, connect the Mini USB port to a PC and use the Modbus Configurator — it talks to the module directly over USB and is independent of the RS-485 settings, so you can read back and reset the values.
Identifying the module / firmware
Register 30001 encodes the firmware (high byte ÷ 10) and the module type code (low byte). For MOD-1TE the type code is 41 (0x29). Reading 30001 over Modbus is a quick sanity check that the gateway, slave ID and serial settings are all correct before TapHome is configured.
