--- title: "WDT-1 watchdog relay for Modbus communication | GridBit" description: "WDT-1 is a controller that keeps the modules at a site working in environments with poor power quality, where voltage surges, harmonics and other anomalies on." url: "https://www.gridbit.tech/hardware/wdt-1" language: "en" translation: "https://www.gridbit.tech/bg/hardware/wdt-1" --- # WDT-1 Watchdog relay that restarts devices when Modbus communication stops [Request a quote](https://www.gridbit.tech/contact?product=WDT-1) - **Relay contact**: Normally open - **Max. relay voltage**: 250 VAC - **Modbus RTU**: RS485 - **Supply voltage**: 9 to 36 VDC Overview ## Where it works WDT-1 is a controller that keeps the modules at a site working in environments with poor power quality, where voltage surges, harmonics and other anomalies on the supply lines cause failures. It has a built-in relay that operates for a programmed time when communication on the Modbus bus stops. It monitors the operation of a GWU module and runs on 9 to 36 VDC. Mounting: 35 mm DIN rail (IEC 60715) 1. Automatic switching of the relay contacts when Modbus communication stops (writing 0 to register 441) 2. Automatic restart of devices that have stopped working 3. Automatic switching off of the relay (for 2 seconds) at a set interval (30 to 1800 seconds) 4. Periodic timer (30 to 1800 seconds) with a pulse output WDT-1 watchdog relay, three-quarter view Datasheet ## Technical data ### Function - **Watchdog module**: Modbus module that monitors the operation of a GWU module ### Power supply - **Supply voltage**: 9 to 36 VDC - **Consumption**: max. 35 mA ### Relay output - **Relay type**: Electromagnetic relay - **Contact type**: Normally open - **Max. operating voltage**: 250 VAC - **Max. contact current**: 5 A (AC-3) / 1 A (AC-1) ### Communication - **Interface**: RS485 - **Protocol**: Modbus RTU - **Baud rate**: 9600, 19200, 57600, 115200 default 9600 - **Parity**: 8N1, 8E1, 8O1, 8N2 default 8N1 ### Environment - **Operating temperature**: -20 to 60 °C - **Storage temperature**: -20 to 80 °C - **Relative humidity**: below 95 %, non-condensing ### Status LEDs - Green On External power supply to the controller present Integration ## Modbus registers The full register map of the module. Filter by address, name or description. ### Input registers | Register | Name | Type | Description | Values | Default | | --- | --- | --- | --- | --- | --- | | 301 | Device type | uint16\_t | Device type, WDT-1 = 1099 | 1099 | | | 302 | HW version | uint16\_t | Hardware version of the device | 030 = HW version 3.0 | | | 303 | SW version | uint16\_t | Software version of the device | 030 = SW version 3.0 | | | 304 | Serial number high byte | uint16\_t | Serial number of the device, high byte | | | | 305 | Serial number low byte | uint16\_t | Serial number of the device, low byte | | | No register matches the filter. ### Holding registers | Register | Name | Type | Description | Values | Default | | --- | --- | --- | --- | --- | --- | | 401 | Device slave address | uint16\_t | Modbus device address | 127 | 127 | | 402 | MODBUS baud rate | uint16\_t | Modbus communication baud rate | 0 to 3 0 = 9600 1 = 19200 2 = 57600 3 = 115200 | 0 | | 403 | Modbus parity | uint16\_t | Parity check mode | 0 to 3 0 = 8N1 1 = 8E1 2 = 8O1 3 = 8N2 | 0 | | 441 | Counter | uint16\_t | Clear the counter to prevent a restart | Write 0 to clear the counter | 0 | | 442 | Threshold | uint16\_t | Time to reset, in seconds | 30 to 1800 | 1800 | | 443 | Test | uint16\_t | Test, switches the relay off | Write 1 to switch the relay off for 2 seconds | 0 | No register matches the filter. Installation ## Dimensions and connection Dimensions in mm Connection diagram On a 35 mm DIN rail Systems ## Used in Street lighting ### [Street lighting management](https://www.gridbit.tech/solutions/street-lighting) Control and monitor street lighting cabinets from one system, with schedules that follow sunrise and sunset, measurements per phase and alarms for every cabinet. Learn more EIM ### [Electrical infrastructure monitoring](https://www.gridbit.tech/solutions/eim) Sensors, analysers and a gateway turn a secondary substation into a monitored asset. The platform shows the transformer and the low-voltage board in real time, with alarms and reports for the grid operator. Learn more [Previous SMU-3 Eight-channel AC voltage detector with Modbus RTU](https://www.gridbit.tech/hardware/smu-3) [Next WDT-4 Modbus watchdog relay, fallback to photo sensor or clock](https://www.gridbit.tech/hardware/wdt-4) ### Transport, warranty and maintenance - **Transport and storage**: Protect the module from shocks and avoid extreme conditions. Store it in the original packaging. - **Warranty**: Two years from the date of manufacture against manufacturing defects. Modifications to the product after the publication date of its documentation release the manufacturer from liability. The manufacturer is not responsible for typographical or other errors in the documentation. - **Maintenance**: Under normal conditions the module needs no maintenance. Light dirt comes off with a dry or slightly damp cloth; for heavier dirt use non-aggressive cleaning products. Always disconnect the power supply first, keep liquids out of the housing and reconnect the power only when the module is completely dry. ## Ask for a WDT-1 quote Tell us the quantity and the project. We answer with a price and lead time. [Request a quote](https://www.gridbit.tech/contact?product=WDT-1) [office@add-bg.com](mailto:office@add-bg.com)