4xRelay USB 160
4xRelay-USB is a device let you to control 4 relays from the PC via USB Virtual COM Port. You can control them by any serial terminal program with few simple ASCII commands, or write your own program to do it. Or use our bundled program to do so.


  • It is powered by an External DC adapter, all relays will remain its state even PC is turn off.

  • Relay state stored at EE, it will resume last state when power on.

  • Simple ASCII command via COM port, easy for programming.


Number of Relays:  4
Connection to PC:  USB (Virtual COM port)
Power:  12V DC (center positive)
Relay Contact:
(AC on resistive load)
 Max. Voltage 240V, Max. Current 5A, Max. Power 120W
Relay Contact:
(DC on resistive load)
 Max. Voltage 30V, Max. Current 4A, Max. Power 120W

About powered by USB:
Well, this unit can powered by USB, but a poor quality of the USB cable or a low voltage output of the USB port (notebook computer) may cause the unit unable to turn on its four relays simultaneously. So powered by USB is not guarantee.

 Package Content:

  •  4xRelay-USB

 Shipping and Payment:

  • Accept PayPal Only
  • Worldwide shipping via Registered Airmail

Please consult with a qualified electrical engineer if you are going to controlling AC devices.

 Front View

 Front View

Rear View

Rear View

Inside View

Inside View

Basic Control Program (Windows)

Basic Control Program

VisualBasic Demo

This example is for Visual Basic 2010 Express which is is free and you can download it from Microsoft.

Linux Console Program

Linux Console Program

Windows Console Program (Visual C++ 2010 Express)

windows set relay 


 How to use?

1) Follow the FTDI Application Note to install the Virtual COM driver. When require connection to device, power the 4xRelay-USB and connect it.

2) After the driver is ready. Decompress 4xRelay-USB.zip to your local harddisk.

3) Run the "4xRelay-USB.exe".

4) Click [Search Port] to find the device.

5) Select the port found.

6) Click [Connect] to connect with the device.

7) Now you can control the relay by click the [Set] or [Clear] buttons.


Connection to device


Serial Command

The serial port is config as 115200 N81. All commands are in ASCII.

Action Command Resp
Get Model Name GI\n 4xRelay-USB\n\r
Get Version GV\n V1.00\n\r
Get Relay n Gn\n
e.g.: G1\n
Turn on Relay n Sn=1\n
e.g.: S1=1\n
Turn off Relay n Sn=0\n
e.g.: S1=0\n