Numato Lab’s 4 Channel Ethernet Solid State Relay Module is a versatile product for controlling electrical and electronic devices remotely from a PC over Ethernet link. 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. For power users, this module can be controlled by writing programs in various programming languages.
- Home Automation
- Lighting Control
- Garden Equipment Control
- Industrial Automation
- Test Fixtures
- DIY and Hobby
- Microcontroller: Microchip PIC18F97J60(1-Mbit Flash Microcontroller with 10Mbps Ethernet communication peripheral)
- Memory: Microchip 25LC1024 serial EEPROM provides 1024 Kbits of storage for both web pages and nonvolatile configuration options
- MAC Address: Separate Serial EEPROM(24AA02E48) with Globally Unique value used as MAC Address
- Reset Jumper: To reset the firmware of board to factory defaults
- The password-protected Web console and Telnet communication interface
- LED indication for Power and individual relay status
- Relay: 4 Solid State Relays with individual LEDs for status
- GPIO: 10 GPIOs, each can be configured as analog inputs
How to use the module
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. 7-12V 1A DC power supply
3. Medium size Philips screwdriver
The pictures above show the basic connection diagrams for AC and DC loads that can be used in most situations. Please make sure to use a freewheeling diode or snubber circuit if the load is inductive. More details about using inductive loads are available elsewhere in this document. Use a Straight Through Ethernet cable for communication when connecting the board to a switch or router. A Crossover Ethernet Cable may be required in some situations if connecting directly to a PC/Laptop port.
It is important to make sure that the wires used to connect loads are sufficiently rated to handle the expected load current. Exercise caution while working with high voltages. Short circuits can cause damage to the module and the PC. The following sections identify individual connections in detail.
The on-board Ethernet port supports Ethernet 10 Mbps transmission speed that helps a computer to communicate and control this module easily. There are two basic network configurations for this board/can be used in two ways.
- Direct connection to Local Area Network(LAN) via common straight-through Ethernet cable.
Eg: Connecting the module to a switch in a network.
- Direct connection to a PC through a cross over Ethernet cable.
Eg: Connecting the module directly to the PC. Some PC/Laptops can detect and adapt to the cable type. In such situations, a straight-through cable also can be used.
This module has four Solid State Relay that can switch up to 3A current. All contacts on each relay are available externally on screw terminals for easy user access. The relays are rated for either AC or DC switching supply voltages. Please see the electrical parameter table for more details. Each relay has two contacts(IN/- and OUT/ +). For AC Relay the contact will be established between IN and OUT contacts when the relay is turned on and will be disconnected when the relay is turned off. For DC relay connect + to OUT and – to IN. The table below summarizes possible relay contact positions.
|Relay State||Connection between IN/- and OUT/+|
This Jumper is used to reset the settings onboard to factory defaults. To execute the factory reset, please follow the steps below.
- Power off the device.
- Configure the Jumper on GS2 to 2-3.
- Power on the device.
- Wait for 10-15 sec until the LED D1 on board Blinks.
- Configure the Jumper on GS2 back to 1-2.
- Power off the board and back on
Please use this feature only for recovering the User name / Password. This action will reset User name, Password, Device ID and also other settings as well. After reset, the board can be accessed using the default User name and Password as shown in the table below
The factory default settings will be as below table.
|IP Address||DHCP Enabled|
Powering Up 4 Channel Ethernet Solid State Relay module
Connect a DC power supply and power up the device as mentioned DC Power Supply section above. A red LED (D2) will glow which indicates active power. Connect the module to a PC or a Switch/Router as mentioned in the Ethernet Interface section above. Run Numato Lab Device Discoverer.jar, 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 command prompt also, 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 in order to access the device.
Accessing the module
The module can be controlled by using one of the two interfaces below.
- Through HTML/Web Page served from the device.
- Through a Serial Terminal Emulator that supports TELNET (Eg: Hyper terminal, Teraterm, PUTTY…)
Accessing the module using web interface
The easiest method for controlling the module is through a web page served from the device. To open the administration web page, type in the IP address into the address bar of any web browser and press enter.
You will be prompted to enter the User name and Password. The default User name and Password is ‘admin‘. You may change the User name and Password once logged in.
Enter the default User name and Password then click OK.
You will be presented with the device home page that shows the status of Relays and GPIOs.
Relay Status and Control
There are 4 solid state relays on the board that can be controlled over Ethernet. Click on the RELAY link on the menu bar to access the Relay configuration page. 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 changes automatically for easy identification.
In the above image, we can see that Relay 1,3 is in ON position and the rest of the relays are in off position. The status of the relay can be viewed on the home page as well.
GPIO Status and Control
This board has 10 general-purpose input/output’s each multiplexed with analog input. Click on the GPIO/ADC link on the menu bar to access the Relay configuration page. The GPIOs can be turned on/off by clicking on the Toggle GPIO button next to the corresponding GPIO.
Individual GPIO can be configured in three modes.
- Digital Input(I/P)
- Digital Output(O/P)
- Analog Input
Analog Input (I/P)
To configure a GPIO as Analog Input, click on corresponding GPIO’s Change Config button. Select Analog I/P radio and click the Submit button.
Individual GPIOs on the board can be turned on/off by clicking the Toggle GPIO button next to the corresponding index. The status change will be displayed on the page immediately for feedback.
All GPIO pins can be used as Analog to Digital Converter inputs as well. The ADC input range is 0 to +3.3V. The ADC can acquire analog signals at the resolution of 10 bits per sample. It is recommended to use a series resistor with the GPIO/ADC pins when interfacing with other circuits. In output mode, GPIOs can source up to 2mA(Refer Technical Specifications for more details).
The table below summarizes the GPIO and Analog to Digital Converter input positions on the header.
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.
In the above image, the firmware version is displayed as 00000008, default device ID 00000000, default User name and Password as ‘admin’. The user can change and save the Device ID, User name and Password as explained in command set (Page No.19) or changing the appropriate field on this page and clicking on the save button on the right side. 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 MAC address, Host Name, and IP Address. The default hostname and IP Address can also be changed according to the user’s wish. After saving changes the board will reboot with the new network settings.
Controlling the module through TELNET interface
The simple set of ASCII based human-readable command set 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 HyperTerminal and TeraTerm.
To use this module with HyperTerminal, please follow the steps below.
- Connect the module to the PC or LAN.
- Open HyperTerminal and enter the IP address corresponding to the module, leave the port number as 23.
- Click OK.
- If everything goes well, you should be presented with a screen as below.
- Select the properties button and do as same as shown below, then press OK.
- Type in the TELNET User name and Password when asked and press enter key.
- Press ENTER key again and the command prompt should appear. Commands listed in the table below (please see section “Sending Commands”)can be entered here now. For example, here is the response to the “ver” command. Using the relay module with TeraTerm is just as easy. Please follow the steps below.
TeraTerm is 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 below (please see section “Sending Commands”) can be entered here now. For example, here is the response for the “ver” command.
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 the TELNET protocol. The following sections give details of the command set and how to use the command set.
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.
|1||ver||None||ver||Returns firmware Version|
|2||id||get/set xxxxxxxx||Id get, id set 12345678||Reads/Sets id of the module|
|3||usr||get/set xxxxxxxx||usr get, usr set admin||Reads/Sets User name|
|4||pass||get/set xxxxxxxx||pass get, pass set admin||Reads/Sets Password|
|5||relay||on/off/read, relay number readall/writeall||relay on 0,relay off 0, relay read 0, relay readall, relay writeall 03||Relay control|
|6||reset||None||reset||Reset relays to default state (all relays turned off)|
|7||adc||read, channel||adc read 0||Read Analog to Digital Converter input|
|8||gpio||set/clear/read, gpio number||gpio set 0||Control General Purpose Input/Output|
The table below has more detailed information about available commands
|1||ver||ver||Returns current firmware version.|
id set xxxxxxxx
|Id get reads the module ID. Id set will assign a new ID to the module. “x” stands for alphanumeric characters including symbols. The new ID must be exactly 8 characters in length.|
usr set xxxxxxxx
|usr get reads the default User name. usr set will assign a new usr name to the module. “x” stands for alphanumeric characters including symbols. The new User name can be 1 – 8 characters length.|
pass set xxxxxxxx
|pass get reads the default Password. pass set will assign a new Password to the module. “x” stands for alphanumeric characters including symbols. The new Password can be 1 – 8 characters length.|
|5||relay||relay on x||Turns a particular relay on. The parameter “x“ stands for the relay number. The relay number starts from zero. See some examples below.
relay on 0 – Turns on relay 0
relay on 1 – Turns on relay 1
|relay off x||Turns a particular relay off. The parameter “x“ stands for the relay number. The relay number starts from zero. See some examples below.
relay off 0 – Turns off relay 0
relay off 1 – Turns off relay 1
|relay read x||Returns the status of a particular relay. The parameter “x” stands for the relay number. The relay number starts from zero. See some examples below.
relay read 0 – Returns status of relay 0
relay read 1 – Returns status of relay 1
The data returned in response to this command will be either “on” or “off” depending on the current status of the relay
|relay readall||Reads the status of all relays in a single operation. The return value will a hexadecimal number with binary value 1 at bit positions for relays in ON state and 0 for relays in OFF state.
Eg: a return value 00 (binary 0000 0000) means all relays are OFF. A value FF (binary 1111 1111) means all relays are ON
relay readall – Returns status of all relays
|relay writeall xx||Control all relays in a single operation. A hexadecimal value must be specified with desired bit positions set to 0 or 1. A value 0 at a bit position will turn off the corresponding relay. A value 1 at a bit position will turn on the corresponding relay.
relay writeall ff – Turns on all relays
|6||reset||reset||Resets all relays to off state which is the default state. GPIOs are not by affected by the command.|
|7||adc||adc read x||Reads the analog voltage present at the ADC input mentioned. “x” stands for the number of ADC input. The response will be a number that ranges from 0 – 1023. Please see examples below.
adc read 0 – Reads analog input 0
adc read 2 – Reads analog input 2
|8||gpio||gpio set x||Sets the GPIO output status to high. Here “x” is the number of the GPIO. Please see examples below.
gpio set 0 – Sets GPIO 0 to high state
gpio set A – Sets GPIO 10 to high state
|gpio clear x||Sets the GPIO output status to low. Here “x” is the number of the GPIO. Please see examples below.
gpio clear 0 – Sets GPIO 0 to low state
gpio clear 2 – Sets GPIO 2 to low state
|gpio read x||Reads the digital status present at the input mentioned. Here “x” stands for the number of GPIO. The response will be either “on” or “off” depending on the current digital state of the GPIO. Please see examples below.
gpio read 0 – Reads GPIO 0 status
gpio read 2 – Reads GPIO 2 status
Analog to Digital Converter
4 Channel Ethernet Solid State Relay Module does support Analog to Digital Conversion on some of the IO terminals. A list of GPIO’s that supports analog function in this product is listed elsewhere in this document. There is no special command is required to execute to switch between analog and digital mode. Executing the “adc” command will set the GPIO to the analog mode and executing the “gpio” command will set the GPIO back to digital mode on the fly. The resolution of the ADC is 10 bits unless otherwise noted. The input voltage range of the ADC is 0 – VDD (this product uses 3.3V power supply, so the range will be 0 – 3.3V). The result will be returned as a number starting at zero and ending at 1023. Zero indicates zero volts at the ADC input and 1023 indicates VDD (3.3V for this product) at ADC input.
Using GPIO's with switches
It is possible to read the position of a switch that is connected to a GPIO. An 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 the 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 the “gpio read” command. Please see the recommended connection diagram below.
Using relay modules with inductive loads
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 the 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 a proper rating is recommended for protecting the relay contacts when a motor is used as a 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 affect 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
|Number of relays||8|
|Number of GPIOs||10|
|Number of analog inputs (Multiplexed with GPIOs)||10|
|Digital circuit power supply voltage (External)||7-12||V|
|Maximum current drawn by digital circuitry||500||mA|
|Maximum IO source current||IO0 – IO9||2mA|
|Maximum IO sink current||IO0 – IO9||2mA|
|GPIO input low voltage||0.15||V|
|GPIO input high voltage||3.3||V|
|GPIO output low voltage||0||V|
|GPIO output high voltage||3.3||V|
|Full scale range||0 – VDD||V|
|Recommended Impedance of Analog Voltage Source||2.5||KΩ|
|Input signal voltage rating||7-12||V|
|Input current rating||5 – 12||mA|
|Operating frequency||47 – 70||Hz
|Operating temperature||-30 – 100||°C|
|Storage Temperature||-30 – 125||°C|
|Maximum switching voltage||250VAC/ 100VDC#||V|
|Maximum switching current||3||A|
|Isolation voltage input to output ||4000||Vrms|
|Maximum switching on response time||8.3 /5 (AC/DC)#||mS|
|Maximum switching off response time ||8.3 /2 (AC/DC)#||mS|
* All parameters considered nominal. Numato Systems Pvt Ltd reserve the right to modify products without notice.
# AC and DC models available. The product does not support both AC and DC at the same time.
Q. What is the connector marked as ICSP on this module?
A. This connector is used to program the onboard microcontroller. This connector is primarily intended for factory use.
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 [email protected] 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 at http://numato.com/distrib.