Ethernet Relay Modules

Numato Lab’s LEO WR8 : 8 Channel Web Relay Module is a versatile product for controlling electrical and electronic devices remotely from a PC over an Ethernet link and is designed for modern IoT, industrial, and smart automation applications.

It combines powerful data acquisition capabilities with seamless cloud connectivity and local control features. With integrated support for Wi-Fi 2.4GHz, MQTT/MQTTS (compatible with AWS, Azure, and other cloud platforms), and REST API, the Module empowers users to monitor, control, and automate processes remotely and securely. Ease of use and wider operating system compatibility are the primary goals behind this product’s design.

This simplicity allows the use of off-the-shelf Terminal Emulation programs such as HyperTerminal and TeraTerm for controlling the module with a simple set of human-readable commands through Telnet/Web page/Wi-Fi and/or REST API commands. For power users, this module can be controlled by writing programs in various programming languages. This highly versatile device allows users to create fully automated systems with minimal setup time. It is ideal for both professionals and hobbyists looking to integrate reliable automation and data acquisition into their systems.

Applications

• Industrial Automation: Monitor sensor inputs and control actuators, machines, or alarms based on configurable logic.
• Smart Home & Building Automation: Automate lighting, HVAC systems, and appliances using environmental data and remote control.
• IoT & Cloud-Based Monitoring: Stream real-time data to AWS, Azure, or private MQTT brokers for centralized dashboards and alerting.
• Environmental Monitoring: Use the onboard temperature and humidity sensor for weather stations, greenhouses, or storage rooms.
• Remote Control Systems: Operate devices from anywhere using the onboard web server or REST APIs.
• Data Logging and Analytics: Log inputs, outputs, and sensor data locally for historical analysis and compliance tracking.
• Smart Agriculture: Monitor field conditions and control irrigation or other systems based on environmental triggers.
• Test Fixtures
• DIY and Hobby

Board Features

• 8 SPDT/SPST Relay Outputs (12V/24V): Control external devices such as fans, alarms, or lighting with 8 independent relay channels, 7A maximum switching current.
• 8 Digital High Voltage Inputs supports Maximum Input Voltage of 24V.
• Relay LED indication: Each relay has individual LEDs for status indication.
• Password-protected Web console, Wi-Fi console, REST API and Telnet communication interface.
• 2-in-1 Sensor: Temperature and humidity sensing in a single device.
• Wi-Fi (2.4GHz): Provides stable wireless communication.
• DIN Rail Support: Supports standard DIN rail for easy installation.
• Cloud Integration: Supports MQTT, MQTTS for AWS, Azure, and more.
• Data Logging: Onboard Data Logging for secure, local storage of sensor and control data.
• Web Server & REST API: Built-in Web Server for configuration, monitoring, and remote control.
• Sensor and ADC Calibration: On-device calibration for accuracy.
• Configuration over USB: Simplified configuration without a network.
• RGB Indicator: Easily shows device status with a color-coded RGB LED.

* All parameters considered nominal. Numato Systems Pvt Ltd reserve the right to modify products without notice.
* SPST Variant Datasheet – HF32FV-G Relay
* SPDT Variant Datasheet – HF3FF Relay

The following section describes how to use this module.

Along with the module, you may need the items in the list below for easy and fast installation.

1. CAT 5e Ethernet Cable(Straight through cable)
2. 12V/24V 1A DC power supply, depending on the relay variant
3. USB Type C Cable
4. Medium-sized Philips screwdriver

Onboard USB port is available; the onboard USB Interface helps to communicate and configure this module seamlessly. This module is detected as a COM port, and the user can configure the module with widely available serial terminal applications, no specialised software required.

It is compatible with most common terminal tools, including:

• Windows
  • Tera Term
  • PuTTY
• Linux
  • GNU Screen
  • PuTTY
• MAC OS X
  • Screen Command
  • CoolTerm

Note: The device is not limited to the above tools and can be used with any standard serial terminal software.

Use a USB-A to USB-C/ USB-C to USB-C cable to connect to a PC. Please visit accessories to buy cables and accessories for this product.

The onboard Ethernet port supports Ethernet 100 Mbps transmission speed that helps a computer to communicate and control this module easily.

You can connect the module to a Local Area Network(LAN) via a common straight-through Ethernet cable.

Eg: Connecting the module to a switch in a network.

The LEO WR8 : 8-channel Web Relay Module offers effortless wireless connectivity with built-in 2.4GHz Wi-Fi, ensuring smooth and reliable network integration. Wi-Fi STA mode can be configured quickly and hassle-free over USB, with no additional hardware required. Once connected, the device efficiently transmits data to the cloud using MQTT/MQTTS, enabling real-time monitoring across multiple platforms. In STA Mode, once the device is configured, it will stay connected to the specified network and continuously publish data to the cloud, ensuring seamless data communication without the need for manual intervention. Secure access is provided through HTTP REST APIs, allowing for robust and real-time data communication. For added convenience, the module features a secure, built-in web interface that can be accessed directly from any browser for easy configuration and monitoring.

SPDT Variant [WR8A, WR8A-24]

This module has 8 SPDT relays (12V/24V), capable of switching up to 7A of current. All relay contacts are available externally through screw terminals for easy user access. The relays are rated for AC switching applications. Please refer to the electrical parameter table for detailed specifications.

Each SPDT relay provides three contacts: COM (Common), NO (Normally Open), and NC (Normally Closed). When the relay is OFF, COM is connected to NC. When the relay is ON, COM is connected to NO. The table below summarizes the possible relay contact positions.

SPST Variant [WR8B, WR8B-24]

This module has 8 SPST relays (12V/24V), capable of switching up to 7A of current. All relay contacts are available externally through screw terminals for easy user access. The relays are rated for AC switching applications. Please refer to the electrical parameter table for detailed specifications.

Each SPST relay provides two contacts: IN and OUT. When the relay is ON, the connection is established between the IN and OUT contacts. When the relay is OFF, the connection is disconnected. The table below summarizes the possible relay contact positions.

This board can be operated using a single DC power supply. Depending on the relay variant, connect either a 12V DC, 1A or 24V DC, 1A power supply to the DC jack on the board. The power supply provides power to both the logic circuitry and the relays.

Connecting the power supply incorrectly can cause damage to the module and/or other devices.

This module has a multifunctional RGB LED Indicator. The device indicates the Power status, Configuration mode, Network status, MQTT connectivity, and Multipurpose switch state.

The LEO WR8 : 8-channel Web Relay Module is equipped with a versatile multipurpose switch that enables a range of device management functions:

Important: Use the Factory reset feature only to recover the Username/Password/Hostname. A factory reset will erase all Network, MQTT, and other settings, restoring the board to its default configuration. After resetting, access the board using the default credentials listed in the table below.

The LEO WR8 – 8 Channel Web Relay Module provides a factory reset feature to restore all settings to their original default values.

How to Perform a Factory Reset

You can initiate a factory reset using either of the following methods:

• Using the Multipurpose Switch: Press and hold the RESET switch for 7 – 10 seconds.
• Using Command Interface: Execute the factory reset command via the USB console.

Important Notes

• This operation will reset all user-configured settings, including:
  • Username and Password
  • Device ID
  • Smart Actions and Timer configurations
  • All other user-configured parameters.
• After reset, the device will revert to factory default credentials, as listed in the table below.

Factory Default Settings

The default configuration after a factory reset is provided in the table below.

Connect a DC power supply and power up the device as mentioned in the DC Power Supply section above. A red LED (PWR) will glow, which indicates active power. For configuration over USB, connect a USB-A to USB-C/USB-C to USB-C cable to the module, and also connect the module to a PC or a Switch/Router as mentioned in the Ethernet Interface section above. Run the Hyper Terminal program or any serial terminal program like PuTTY, TeraTerm, etc.

NB: By default, the module is configured with factory settings. To log in to USB configuration settings, users need to send a ‘reboot’ command from telnet or do a factory reset.

Select the module’s COM port and use the default settings, similar to the images below and connect.

Users will be prompted to enter the User name and Password. The default User name is ‘admin‘ and Password is ‘admin1234‘. You may change the User name and Password once logged in.

If the user name and password are correct, we will be able to see the login success message.

Example commands and results after executing the commands.

Connect a DC power supply and power up the device as mentioned in the DC Power Supply section above. An RGB LED will glow Red for 2 seconds, which indicates active power. Connect the module to a Switch/Router as mentioned in the Ethernet Interface section above. Run Numato Lab Device Discoverer.jar, and click on Discover Devices. The window will display the IP address, Host Name, MAC Address, and Other information.

IP Address and MAC Address can be seen in the command prompt also, only after connecting the module through the web page. Open the command prompt and type the command ‘arp -a‘. This will display the available network interfaces and connected devices along with the MAC address and IP address of each device. Look for the IP address that corresponds to your device’s MAC address. The MAC address for each Relay Module is printed on a label on the board for your convenience. Use the IP address obtained to access the device.

The module can be monitored and controlled by using the interfaces below.

1. Through HTML/Web Page served from the device – Ethernet interface.
2. Through HTML/Web Page served from the WI-Fi interface.
3. Through a Serial terminal Emulator that supports TELNET (Eg: Hyper Terminal, TeraTerm, PUTTY…).
4. Through REST API commands.

The easiest method for controlling the module is through web page served from the device. To open the administration web page, type in the IP address in to the address bar of any web browser and press enter.

You will be prompted to enter your Username and Password. The default username is ‘admin,’ and the default password is “admin1234”. Once logged in, you may change the Username and Password.

Enter the default User name and Password, then click Sign In.

You will be presented with the device home page that shows the status of Relays and GPIOs

8 Relays on the board can be controlled over Ethernet/WiFi. The Relay Index shows the corresponding relay on board. Relays on the board can be turned on/off by clicking the Toggle Relay button next to the corresponding relay index. The Status of the relays change automatically for easy identification.

This board has 8 general-purpose high-voltage inputs. The status of GPIOs is shown on the home page.

The device Settings page displays the current firmware version, Device ID, Account Settings, and Basic Network Settings. A logged-in user can change and save the Device ID, User name, Password, and network settings.

The user can change and save the Device ID, User name, and Password as explained in the command set or by changing the appropriate field on this page and clicking on the save button on the right side, and reboot the page from the Device Management section. The User name and Password can be reset to factory defaults via Factory Reset explained elsewhere in this document. The Basic Network Settings shows the Device’s MAC address, Host Name, DHCP Status, IP Address, Subnet Mask and Gateway. The default hostname and IP Address can also be changed according to the user’s wish. After saving changes, and rebooting the board will reboot with the new network settings.

The easiest method for controlling the module is through web page served from the device. To open the administration web page, type in the IP address in to the address bar of any web browser and press enter.

You will be prompted to enter Your username and Password. The default username is ‘admin,’ and the default password is “admin1234”. Once logged in, you may change the Username and Password.

Enter the default User name and Password then click Sign In.

You will be presented with the device home page where you can monitor the sensor data.

The Device Info section provides detailed information about your device. This section is read-only, which means you cannot modify the device information here, but you can refer to it when needed.

These details are displayed in a simple, easy-to-read format.

In the User Account section, you can manage your web login, including updating your Username and Password. This is important for keeping your account secure and ensuring only authorized users can access the device settings.

Important Note: Your password will only be updated if both the New Password and Confirm Password fields match exactly. If there is a discrepancy, a Warning message will be displayed, and you will need to correct it before proceeding.

Important Update Information: Once you update the User Account Password, the web login password will be updated simultaneously. This means that the new password will be used for the web login to your device’s dashboard. Make sure to remember this new password for all future logins to your device.

The Firmware Update section allows you to keep your device up to date with the latest features, improvements, and bug fixes. Firmware updates can be performed only through the NET1 (Wi-Fi) interface.

Important: Do not upload any unauthorized images via OTA. Doing so may permanently damage the device.

In the Device Management section, you can perform essential actions to manage your device, including rebooting the device and restoring it to its factory settings.

Important Note:  Factory Reset is a permanent action. Once performed, all user-set data and logged sensor data will be erased. This action cannot be undone,  make sure to back up any important data before performing a factory reset.

The Network Settings section allows you to configure the network connection of the device. This includes the :

1. Ethernet Network Settings
2. Wi-Fi Station Settings

The Ethernet Network Settings section allows you to configure the device’s wired network connection.

After entering the required network parameters, click Submit to apply the settings.

The Wi-Fi Station Settings section allows the device to connect to an existing Wi-Fi network.

After entering the required network parameters, click Update WiFi Station Settings to apply the settings.

After a reboot or a power reset, the module can be accessed via the DNS Hostname or the IP Address.

• Accessing via DNS Hostname:
  • The device will be accessible via its DNS hostname. By default, the device will be configured with a device specific unique hostname. The device can be accessed with the postfix “.local” example:  hostname.local.
• Accessing via IP address:

  • If the device was configured with a static IP address, you can access it directly by entering the static IP address into your browser.

  • If the device was set to use dynamic IP (DHCP), you can either check the IP address assigned to the device through your router’s DHCP table or use a “arp -a” on command tool and check the IP assigned to your device MAC.

The MQTT/MQTTS Settings section allows you to configure the communication between your device and the MQTT broker. You can choose to use either MQTT (unencrypted) or MQTTS (secure, encrypted MQTT).

The simple set of ASCII based human readable command sets supported by this module makes controlling relays easy via TELNET protocol very easy. The following sections give examples of how to use the module with PuTTY and TeraTerm.

To use this module with PuTTY, please follow the steps below.

• Connect the module to the LAN.
• Open PuTTY and enter the IP address corresponding to the module, leaving the port number as 23.
• Click Open.
• If everything goes well, you should be presented with a screen as below.
• Type in the TELNET User name and Password when asked and press enter key.
• Commands listed in the table in  section “Sending Commands” can be entered here now. For example, here is the response for “ver” command.
• Using the relay module with TeraTerm is just as easy. Please follow the steps below.

TeraTerm is an open source software. A free copy can be downloaded from http://en.sourceforge.jp/projects/ttssh2/releases/

• Run TeraTerm and type in the IP address corresponding to the module in the “New connection” dialog and click OK.
• Then select the terminal setup from the setup button and make sure the settings are as shown below, and press OK.
• Type the User name and Password when asked.
• Press ENTER key and the command prompt should appear. Commands listed in the table in section “Sending Commands” can be entered here now. For example, here is the response for “ver” command.

This module supports REST API commands.

Refer to the ‘REST API Command Set‘ knowledge base to know more.

Below is the example image related to controlling these modules through REST API commands.

fig 1: Displays device ID

One of the most powerful features of this module is the simple easy to use command set it supports. This command set allows for a very simple interface to access the features of the module through TELNET protocol. The following sections give details of the command set and how to use the command set.

This product supports a very simple command set that is designed to be less cryptic and easy to use manually (using terminal emulation programs that support TELNET) or through a program written in one of the many supported languages

List of currently supported commands.

The table below has more detailed information about available commands.

It is possible to read the position of a switch that is connected to a GPIO. A SPST or SPDT switch is recommended to use with GPIO’s. Push switches do maintain the contacts closed only for a very short time so using them is discouraged. The fundamental idea of using a switch with GPIO is to have the switch cause a voltage level change at the GPIO pin when pressed. Usually this is achieved by using an external pull-up resistor along with the switch. The pull up resistor is connected between the GPIO and VDD and the switch is connected between the GPIO and ground. When the switch is not pressed, the pull-up resistor will cause the GPIO to stay at VDD voltage level. When the switch is pressed, the GPIO is short circuited to ground and stays at zero voltage. This change in voltage and thus the position of the switch can be read using “gpio read” command. Please see the recommended connection diagram below

It is important to take additional care when using relays with inductive loads. An inductive load is pretty much anything that has a coil and works based on magnetic principles like Motors, Solenoids and transformers. Inductive loads produce back emf when the magnitude of the load current changes. The back emf can be in the order of tens or even hundreds of voltage (See this Wikipedia article http://en.wikipedia.org/wiki/Counter-electromotive_force). This effect is most severe when power is disconnected from inductive load because the rate of change of current is maximum at that point. Even though the back emf lives only for a very short time (a few milliseconds) it can cause sparks between the relay contacts and can deteriorate the contact quality over time and reduce the life span for the relays considerably.

So it is important to take countermeasures to suppress the back emf to acceptable levels to protect relay contacts. Usually this requires connecting electronic devices in parallel with the load such that they absorb the high voltage components generated by the load. For solenoids, connecting a diode (fast switching diode is recommended) in parallel to the load (in reverse direction to the load current) is very effective. A diode used for this purpose is usually called a freewheeling diode. Please see the diagram on the right for connection details.

A capacitor with proper rating is recommended for protecting the relay contacts when a motor is used as load. The capacitor should be rated enough to withstand the back emf that is generated by the motor. Please see the diagram below for connection details.

Please note that the relay modules are NOT shipped with back emf suppression devices pre-installed. The exact kind of suppression device and the parameters of the selected device can vary depending on the load itself. Some of the parameters that affects the suppression device selection are the inductance of the load, power supply voltage, load current, physical size/structure of the load etc.. It is obvious that it is impossible for us to predict these parameters and design required back emf suppression device and incorporate that on the board. So we believe this is a task best left to the module user. There is an excellent article on designing back emf suppression on Wikipedia at http://en.wikipedia.org/wiki/Flyback_diode

Q. I need a customized version of this product, can Numato do the customization for me?
A. Yes, we can definitely do customization but there may be minimum order requirements depending on the level of customization required. Please write to sales@numato.com for a quote.

Q. Where can I buy this product?
A. All Numato products can be ordered directly from our web store http://www.numato.com. We accept major credit cards and Paypal and ship to almost all countries with a few exceptions. We do have distributors in many countries where you can place your order. Please find the current list of distributors here.