UR8A – 8 Channel USB Relay Module | Numato Lab Help Center

1.Introduction

The Numato Lab’s UR8A – 8 Channel USB Relay Module is a precision-engineered control interface designed for professionals who demand reliability, simplicity, and intelligent automation in a single, compact module.

The UR8A module enables effortless relay control and digital input monitoring over USB through a clean, human-readable command interface. This streamlined approach removes unnecessary complexity, allowing developers, engineers and integrators to focus on building systems, not decoding protocols.

Crafted with a modern, industrial-grade architecture, the UR8A – 8 Channel USB Relay Module is built to perform consistently in all environments.

At its core lies the powerful Smart Action Engine, transforming the device from a simple interface into an autonomous control unit. With support for intuitive, rule-based automation, the module can independently execute logic such as event-triggered actions, elimination the need for constant host supervision.

To further enhance precision and system resilience, the module includes:

Relay Timer for accurate and repeatable output behavior.
Integrated IO Failsafe Engine to ensure safe operations.

As a result the UR8A – 8 Channel USB Relay is a device that delivers clarity in control, intelligence in operation, and confidence in deployment.

Whether used for industrial automation, testing infrastructure, or system integration, the UR8A – 8 Channel USB Relay Module sets a new standard for smart, reliable, and user-centric control solutions.

Applications

Industrial Automation and Control
Building and Facility Automation
Remote Monitoring and Control Systems
Power Management and Sequencing
Safety and Failsafe Systems
Edge Automation (Standalone Operation)
Test and Measurement Automation
DIY and Hobby

Board Features

8 Relay Outputs (7A Switching Capacity)
8 High-Voltage Digital Inputs (Up to 24V)
Dedicated Relay Status LEDs
Secure Command-Line Interface over USB
Smart Action Engine (Rule-Based Automation)
Advanced Relay Timer Functionality
Configurable Failsafe Input
DIN Rail Mount Compatibility
RGB Status Indicator
Device Reset and Factory Reset Switch

Parameter *	Value	Unit
Basic Specifications
Number of relays	8
Number of digital Inputs	8
Digital circuit power supply voltage (External)	12/24	V
Maximum current drawn by digital circuitry	300	mA
Digital Inputs Specifications
Minimum DI sink current	2.05	mA
Maximum DI sink current	30	mA
Recommended sink current	10	mA
Maximum Low Voltage (VIL)	10.2	V
Minimum High Voltage (VIH)	10.5	V
Maximum High Voltage	24	V
Relay Specifications
Nominal relay coil voltage	12/24	V
Nominal coil power consumption (per relay)	450	mW
Relay contact material	Silver Alloy, silver metal-oxide
Contact rating	10A 250VAC 10A 30VDC
Maximum switching voltage	250VAC/30VDC
Maximum switching current (recommended)	7	A
Maximum switching power	2500VA/300W
Contact resistance	100	mΩ (at 1A 6VDC)
Insulation resistance	1000	MΩ
Life expectancy (Electrical)	100000 50000	Operations (at 10A 250VAC resistive load, room temp) Operations (at 10A 250VAC, resistive load, at 85°C)
Life expectancy (Mechanical)	10000000	Operations
Maximum switching on response time	1	second
Maximum switching off response time	9	second
shock resistance (Functional)	294	m/s2
Shock resistance (Destructive)	980	m/s2
Vibration resistance	10Hz to 55Hz, 1.5mm DA
Other Information
USB Vendor ID	0x2A19
USB Product ID	0x0C1B

Action	LED Indication	Function
Single Click	The Red LED briefly turns OFF and ON, indicating that the device is restarting.	Device Reset: Resets the device and reinitializes.
Press for 5-7 seconds	The Red LED blinks continuously while the factory reset process is in progress.	Factory Reset: Device erases all the settings and restores to factory defaults.

User name	admin
Password	admin1234
Device ID	00000000
Smart Action	Disabled
Relay Power-On	Disabled
GPIO Notify Feature	Disabled
IO Failsafe	Disabled

Error Code	Error Name	Description
-3	Invalid Command	The entered command is not recognised by the device
-2	Invalid Argument	One or more parameters are incorrect
-51	Invalid Relay Timer Limit	Timer delay is outside the allowed range

No.	Command	Parameters	Example	Description
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	usr auth	get/on/off	usr auth get, usr auth on, usr auth off	Returns User Auth status, Enable/Disable Authentication
6	relay	on/off/status [relay number]/ on all/off all/ write [relay_group] [relay_map]/ pwron [relay_group] [relay_map]/ tmr get [relay_number]/disable [relay_number]/[relay_number] [mode] [delay_seconds]	relay on 000,relay off 000, relay status 000, relay on all, relay off all, relay write A 00ff, relay poweron A 00ff, relay tmr get 000, relay tmr disable 000, relay tmr 000 M0 2	Relay Control
8	gpi	gpi read [input number], gpi notify on/off/get	gpi read 000, gpi read, gpi notify on, gpi notify off. gpi notify get	Monitor General Purpose Input
11	smart	get/-i/-r/disable/ [input] [mode] [target_output] [value]	smart get 000, smart -i 000, smart -r 000, smart disable, smart 000 L 000 1	Read configured data, clear configured input, clear configured relay, disable entire smart action feature, configure smart feature
7	fs	get input_number/reset/disable/ [input] [mode] [relay_group] [relay_map]	fs get 000, fs reset, fs disable, fs 000 L A 0012	Read status of IO failsafe, Manual Reset Failsafe, Disable Failsafe, Configure Failsafe
9	info	none	info	Display information about the module including Smart Action, Power-on status, and IO Failsafe
10	power	reset	power reset	Power reset does a soft-reset.

No.	Command	Example	Description
1	ver	ver	Returns current firmware version.
2	id	id get 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.
3	usr	usr get 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.
4	pass	pass get 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	usr auth	usr auth get	Returns USB Authentication status
		usr auth on	Enable USB Authentication
		usr auth off	Disable USB Authentication
6	relay	relay on xxx	Turns a particular relay on. The parameter “xxx“ stands for the relay number. The relay number starts from zero. See some examples below. relay on 000 – Turns on relay 0 xxx can be 000-007
		relay off xxx	Turns a particular relay off. The parameter “xxx“ stands for the relay number. The relay number starts from zero. See some examples below. relay off 000 – Turns off relay 0 xxx can be 000-007
		relay status xxx	Returns the status of a particular relay. The parameter “xxx” stands for the relay number. The relay number starts from zero. See some examples below. relay read 000 – Returns status of relay 0 xxx can be 000-007 The data returned in response to this command will be either “on” or “off” depending on the current status of the relay
		relay status	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 on all	Turns on all relays.
		relay off all	Turns off all relays.
		relay write A 00xx	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 writea A 00ff – Turns on all relays. The 'A' denotes group of relays 0-15.
		relay pwron A 00xx	Sets the relay power on value. relay poweron A 0003 : Turn OFF and ON relays on power-on the module according to the specified hexadecimal value. A - Group of first 16 Relays. 0 – Turn OFF the relay, 1 – Turn ON the relay. '0003' - 0000 0000 0000 0011 : Relays 0 and 1 will be turned on once entered to the telnet mode or on power reset. xxxx can be in range 0000-00FF : UR8A xxxx can be in range 0000-FFFF : UR16A
		relay tmr get xxx	Returns the current configuration and status of a specific relay timer. The parameter "xxx" stands for the relay number. The relay number starts from zero. See some examples below. relay tmr get 000 - Returns the timer status for Relay 0 xxx is relay number (range: 000 to 007) Response to the command: The device responds with the current timer configuration, which includes: - Timer Mode - Delay Value (in seconds)
		relay tmr disable xxx	Disables the relay timer configuration on relay xxx, where xxx is relay number (range: 000 to 007)
		relay tmr disable	Disables entire relay timer feature.
		relay tmr [relay_number] [timer_mode] [timer_delay]	This command is used to configure the timer behavior of a specific relay channel, enabling precise control over relay operation based on time. relay_number Specifies the relay to be configured Range: 000 to 007 timer_mode Defines the operating mode of the relay timer Modes: M0 – Delayed ON M1 – Delayed OFF M2 – Toggle Timer timer_delay Sets the time delay for the selected mode, in seconds Range: 1 to 3600 seconds Examples `relay tmr 000 M0 1` – Turns ON Relay 0 after a delay of 1 second `relay tmr 000 M1 4` – Turns OFF Relay 0 after a delay of 4 seconds `relay tmr 000 M2 10` – Toggles Relay 0 every 10 seconds Important Notes Timer configurations are persistent and remain active even after a power reset A configured timer continues to operate until it is explicitly disabled or the device is factory reset
8	gpi	gpi read xxx	This command reads the current state of a specific digital input (GPI). Command Format `gpi read xxx` xxx - Digital input number, Range: 000 to 007 Response Format `0 or 1` 0: Input is LOW, 1: Input is HIGH Description The command returns the instantaneous logic level of the selected digital input. Example `gpi read 000` Returns 0 or 1 depending on the current state of GPI 0 Notes: Ensure the input number is within the valid range (000–007) The response reflects the real-time state of the input at the moment of execution
		gpi read	This command reads the current status of all digital inputs in a single operation and returns the values grouped by input channels. Command Format `gpi read` Response Format `A:XXXX` XXXX - Current digital input state (hexadecimal value) Description The returned value represents the state of all digital inputs in the selected group: Each bit corresponds to one input channel 0 - GPI LOW, 1 - GPI HIGH Example `A:00FF` ALL inputs in Group A are HIGH `A:0001` GPI 0 is HIGH, all other inputs are LOW Group Representation A - Group A (First 16 digital inputs) Each bit represents one input: 0 - GPI LOW, 1 - GPI HIGH Value Range UR8A: `0000` to `00FF` (8-bit) UR16A: `0000` to `FFFF` (16-bit)
		gpi notify on	This command enables digital input (GPI) change notifications. When enabled, the device monitors input state changes and sends a notification to the host whenever a change is detected. Notification Format Notifications are sent in the following format: `A:XXXX/YYYY` XXXX - Current input state YYYY - Previous input state Example `A:00FE/00FF` Previous state: `00FF` Current state: `00FE` This indicates that the GPI 0 changed from HIGH(1) to LOW (0), which triggered the notification. Group Representation A - Group A (First 16 digitalinputs) Each bit represents one input: 0 - GPI LOW, 1 - GPI HIGH Value Range UR8A: `0000` to `00FF` (8-bit) UR16A: `0000` to `FFFF` (16-bit)
		gpi notify off	This command disables the GPI change notification feature. Command Format `gpi notify off` Response Format `Gpi Notify Disabled` Description Disables automatic notifications for digital input state changes. Once disabled, the device will no longer send updates to the host when input states change. Example `gpi notify off` Disables GPI change notifications
		gpi notify get	This command returns whether the GPI change notification feature is enabled or disabled. Command Format `gpi notify get` Response Format `Gpi Notify Enabled` or `Gpi Notify Disabled` Description Returns the current status of the gpi change notification feature. Example `gpi notify get` Returns `Gpi Notify Enabled` or `Gpi Notify Disabled`
	smart	smart get xxx	This command returns the current Smart Action configuration for a specific digital input channel. Command Format `smart get xxx` xxx – Digital input number (Range: 000 to 007) Response Format `M:L R:000:H` M – Input mode (L: LOW, H: HIGH, F: FOLLOW) R – Relay number H / L – Trigger value (HIGH / LOW) Description Returns the Smart Action settings configured for the selected digital input Includes operating mode, mapped relay outputs, and configured trigger values Example `smart get 000` Returns Smart Action configuration for Digital Input (GPI) 0 Notes Ensure the input number is within the valid range (000–007) If no Smart Action is configured, the response will indicate `I:000 not mapped`
		smart -i xxx	This command disables the configured digital input for the specified channel. Command Format `gpi disable xxx` xxx – Digital input number (Range: 000 to 007) Description Disables the selected digital input channel. Example `gpi disable 000` Disables Digital Input (GPI) 0 Notes Ensure the input number is within the valid range (000–007).
		smart -r xxx	This command disables the configured relay for the specified channel. Command Format `relay disable xxx` xxx – Relay number (Range: 000 to 007) Description Disables the selected relay channel. Example `relay disable 000` Disables Relay 0 mapped to smart action Notes Ensure the relay number is within the valid range (000–007).
		smart disable	This command disables the Smart Action feature for all input channels. Command Format `smart disable` Description Disables all configured Smart Actions. Once disabled, no digital input will trigger any relay output based on Smart Action logic. Example `smart disable` Disables Smart Action feature for all inputs
		smart [input] [mode] [target_output] [value]	This command configures the Smart Action feature. Smart Action maps digital inputs to relay outputs and automates relay control based on input state. Command Format `smart xxx mode target_output value` Parameters xxx – Digital input number (Range: 000 to 007) mode – Defines the trigger condition for the relay L – Trigger when input is LOW H – Trigger when input is HIGH F – Follow mode (relay follows input state) target_output – Relay to be controlled by the selected digital input (Range: 000 to 007) value – Relay output state when triggered 0 – Relay OFF 1 – Relay ON Not required in F (Follow) mode Description Each command links a digital input (same index as xxx) to a relay output. The relay action depends on the selected mode and trigger condition. Examples `smart 000 L 000 1` – When digital input 0 goes LOW, Relay 0 turns ON `smart 001 H 002 0` – When digital input 1 goes HIGH, Relay 2 turns OFF `smart 003 F 003` – Relay 3 follows digital input 3 (LOW → OFF, HIGH → ON) Notes Digital input index corresponds to the input used in the command. Follow mode (F) continuously mirrors input state without delay.
	fs	fs get xxx	Returns the IO failsafe configured on xxx. where xxx is digital input 000. Command response: returns the configured digital input mode and mapped relays.
		fs reset	This command is used to perform manual failsafe reset to continue the device operation.
		fs disable	This command disables the IO failsafe feature completly.
		fs [input] [mode] [relay_group] [relay_value]	This command is used to configure the IO Failsafe feature, enabling the module to automatically set relay states based on a defined digital input condition. It is designed to ensure predictable and safe system behavior during fault conditions or specific input event. input: Specifies the digital input used for failsafe triggering On UR8A, only Digital Input 0 supports this feature mode: Defines the input condition that triggers the failsafe action L – Trigger when input is LOW H – Trigger when input is HIGH relay_group: Specifies the relay group to be controlled A – Group A (supported on UR8A) relay_value: Defines the output state of relays when failsafe is triggered, using a hexadecimal value Each bit represents a relay state 0 – Relay OFF 1 – Relay ON Example: 0003 - 0000 0000 0000 0011 - Relays 0 and 1 ON, all others OFF Value Range UR8A: 0000 to 00FF UR16A: 0000 to FFFF Examples `fs 000 L A 0012` When Digital Input 0 goes LOW, relays are set according to 0012. - Relay 1 and Relay 4 turn ON, all others turn OFF. `fs 000 H A 0012` When Digital Input 0 goes HIGH, relays are set according to 0012. - Relay 1 and Relay 4 turn ON, all others turn OFF.
9	info	info	Display information about the module including Smart Action, Power-on status and IO Failsafe
10	power reset	power reset	Power reset does a soft-reset.

Relay State	IN to OUT Connection	Load Condition
OFF	Open	Load Disconnected
ON	Closed	Load Energized

USB Relay Modules