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USB Eight Channel Relay Board for Automation

This is relay card with eight SPDT relays which is controlled via PC USB port. We have created flexible software for this USB relay board, that allows you to make simple automation project or control from command line. We provide various examples in .NET, Java, VB6, BCB6, Labview, Python and others.

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Price: $39.50
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This is relay board with 8 SPDT relays which is controlled via USB protocol. The main purpouse of this relay board is to help you building projects regarding robotics and home automation. You may control differenet electrical devices like lights, DC motors, pneumatic cylinders, lasers and so on. Hints for creating user application in different platforms (Visual C++, Borland C++ Builder, Visual Basic and so on) are provided. Each such board require one USB port. The more USB ports you have the more Relay boards you may connect. Supported by DRMv3 Software. We have Windows examples for VB6, BCB6, Java (netbeans), VB.NET 2010 Express, C++.NET 2010 Express - please contact with us for more details.



  • USB communication with computer
  • Power supply voltage selectable during purchase:
    • 12VDC, 300 mA
    • 24VDC, 200 mA
  • Protection against reversle polarity: YES (since hardware revision Rev.:02/11/2016)
  • 8 SPDT relay channels (the type depends on the stocks quantity in our store):
    • TONGLING - JQC-3FF-S-Z (10A / 250VAC, 15A / 120VAC, 10A / 28VDC)
    • SUNHOLD - RAS xx15 (10A / 250VAC, 15A / 120VAC, 15A / 24VDC) 
  • All relays are OPTO-ISOLATED (since hardware revision Rev.:02/11/2016)
  • PCB parameters: FR4 / 1.5mm / two layers / metalized holes / HAL / white stamp / solder mask
  • Extra PCB openings for better voltage isolation
  • Doubled high current tracks
  • Chip: FT245RL. Datasheet - here
  • Power led
  • Relay leds
  • Size: 106mm / 78mm / 16mm
  • Mounting holes diameter: 3mm
  • Supported by DRMv3 Software (Windows, Linux, Raspberry PI) - New
  • Supported by DRM software (Windows, Linux, Raspberry PI)
  • Supported by Denkovi Command line tool (Windows, Linux, Raspberry PI)
  • Software Examples - here
  • Documentation - here



  • High quality
  • Low cost
  • Free software with many functions
  • Control electrical devices according weekday/date/time
  • Create timers or pulses with our software


  • Home automation
  • Robotics
  • Alarms
  • Timers
  • Open doors and windows via PC
  • Aquariums applications


Communication with the boards

Each such board is shown as separate virtual com port (VCP) on your PC. The relay board outputs are controlled by FT245RL. It has 8 bit data output register. When data is sent to the register the outputs are set. Be sure "Synchronous Bit-Bang Mode" is selected! FTDI provides Bit-Bang Mode documentation. See here.



  • When the board is connected to the PC and/or the PC is restarted, the relays(1,3,5) will be toggled several times. This is because of the structure of the FTDI chip. (You can avoid this if you first connect the USB cable and then supply the relay board). This problem is fixed since hardware revsion Rev.:02/11/2016
  • There is no protection against reversed polarity! If the +Vcc and GND are reversed the board will be damaged! Such protection is added since hardware revsion Rev.:02/11/2016
  • The board is tested with 10 meters USB cable and works fine.
  • The board can not work without computer.


Denkovi Relay Command Line Tool

The main goal of this project is to help you to use our USB relay boards easily and without any specific knowledge how do they work. This tool is actually shell for all our USB relay boards and it does not matter which is the relay board, the command is the same. Just type one command and the the tool will set, get relay status or even will take temperature value from the board sensor (if any). It can be integrated in other software and you don't need to know much about how the USB relay board protocol. With this tool it is like a "game" and it takes literaly minutes to create for example PHP script and control the USB relay board from smartphone browser.

Typical applications for this software are:

  • Create desktop icons to turn particular relays
  • Create BAT/BASH files to make more complex logic (like timers for example)
  • The commands can be executed from PHP script
  • Control our USB relay boards from Android / iPhone mobile devices
  • The USB relays can be controlled from each software/platform which can run external executable files or commands in command line promt

Example commands:

LIST COMMAND - lists all devices connected to computer.

java -jar DenkoviRelayCommandLineTool.jar list 


STATUS COMMAND - display relay(s) status(es).

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 8 1 status

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 8 all status


SET COMMAND - set relay(s) state(s).

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 8 5 1

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 8 all 0

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 8 turn 10101010


TIMER COMMAND - exectues time-critical operations. Well known fact is that every time when we run the command line tool the jvm is runned and this takes significant time. Many users contacted us with requests to execute timer commands for time-critical operations. That's why we added such command. It can perform single pulse, many pulses and even cycles with more complex sequences of pulses and every pulse can be with different time (in miliseconds). Please note the state bits must be equal to the relay numer!

java -jar DenkoviRelayCommandLineTool.jar id=1 4 timer 1,1111,10,0000,50,1111,25 //makes all relays ON for 10ms, all OFF for 50ms and all ON for 25ms

java -jar DenkoviRelayCommandLineTool.jar id=1 8 timer 5,11111111,10,00000000,100 //makes all relays ON for 10ms and all OFF for 100ms - 5 times

java -jar DenkoviRelayCommandLineTool.jar id=1 16 timer 5,1000000000000000,10,0000000000000000,1000 //makes first relay ON for 10ms and OFF for 1sec - 5 times


For more information - here

For download - here

Windows: tested on XP, Vista, 7 and 8

Linux: tested on Ubuntu and OpenSuse



Demo video how you can control the USB 8 Channel relay board from command line, browser and tablet the same time because of our command line tool.


Access via software DRMv3

This device is supported by DRMv3 Software.

The device can be found in the device list under the default name: USB 8 Relay





USB 8 Relay Manager

This is application that allows the USB 8 relay board to be controlled from your PC. There is two modes - Manual Mode and Timer mode. You may open many USB boards and select wich one to control. There are 8 indicators representing each relay channel led from the board.

Screenshot Manual Mode - here

Screenshot Timer Mode - here

For more information about USB 8 Relay Manager, screenshots and detailed description - here

Download the last version (install package) - USB8RelayManager.exe

Download the last version (install archive) - USB8RelayManager.rar



Denkovi JExtraPack

Denkovi JExtraPack contains 3 applications. Each of these applications are written in Java, so JVM is required. Each application can control up to 10 USB relay boards so you will need of course FTDI VCP drivers. We provide single installation file and everithing is included in it.

Screenshot Manager - here

Screenshot Timer - here

Screenshot Alarm - here 

For more information about Denkovi JExtraPack, screenshots and detailed description - here

Download the last version (install package) - DenkoviJExtraPack.exe

Download the last version (install archive) - DenkoviJExtraPack.rar



More videos  


Demo video - Control USB Eight Channel Relay Board with Android Tablet




Demo video with DRM Software and USB Eight Channel Relay Board



Demo Video - DRM Software and 4 x USB Eight Channel Relay Boards





Denkovi software


Third parity software

  • to be added later...


 Software examples

  • Some of the source code demos are not public, and the download links will be sent to your email after purchase or by request.
  • Delphi Lazarus - example how to set the status of the relays.
  • QT C++ - windows example how to set and read the status of the relays.
  • JAVA (netbeans) -  Example how to set/get the relays and I/O status.
  • Visual Basic 6 - Example how to set the relays
  • .NET (C#, C++, Visual Basic) - Example how to set and get the relays
  • LabVIEW 2011 (screenshot) -  Example how to set and read the status of the relays. For download please contact us.
  • drcontrol - a command utility written in Python and uses the pylibftdi. Author: Sebastian Sjoholm (
  • Python example soure code for Windows (Thanks Peter Bingham - p.bingham at camlintechnologies dot com)
USB relay board
USB eight relay board
USB 8 SPDT relays

by Marcel, 17 Aug 2017

quick, simple and clear

by Tim, 15 Mar 2017

The new version is more than great!

by Paul, 16 Nov 2016

Your relay boards are awesome! :) Thank you!

by Mike Myers, 03 Mar 2013

WOW! This is one the most versatile pieces of equipment I have ever owned! I run an internet radio station and I use it to switch audio outputs on two different computers. There are so many other uses I will find for this device. This is exactly what I was looking for at a fraction of the cost I thought I was going to have to pay. Thank you so much!

by ri, 15 May 2012

this usb relay bord is very can be use on so many things and do so many things.i got my home and garden running on it doing all difrent ben running for the last 3 years and still going strong.

by Gerri, 26 Dec 2011

So eixcted I found this article as it made things much quicker!


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