The Yocto-Relay device contains two USB-driven miniature unipolar relay switches. You can drive by software each relay input to one of two individual outputs (computer-driven switch). To make it easier to test your project, four leds positioned on the front side of the connector show the output currently active for each relay.

This product is designed to stand up to 60 VDC (30 VAC) and a current of 2A, but no more than 60W. Be aware that using a relay to drive inductive loads (motors, transformers) may lead to accelerated aging of the relay. Please refer to the documentation for hints on reducing this type of problems.

This device can be connected directly to an Ethernet network using a YoctoHub-Ethernet, to a WiFi network using a YoctoHub-Wireless-n and to a GSM network using a YoctoHub-GSM.

Yocto-Relay Yocto-Relay

USB cables and enclosures to be ordered separately.

CHF 34.48

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Hardware release:Rev. B
Product name:Yocto-Relay
USB connector:micro-B
Max switching power:60W
Operate time:5ms (max)
Release time:7ms (max)
Max withholding voltage:400V DC
Max working voltage:60V DC
Max working voltage (AC):50V r.m.s.
Protection class, according to IEC 61140:class III
USB isolation, dielectric strength:0.25kV
Normal operating temperature:5...40░C
Extended operating temperature2:-30...85░C
Supported Operating Systems:Windows (PC + IoT), Linux (Intel + ARM), macOS, Android
Drivers:Driverless, no driver needed
API / SDK / Libraries:C++ Obj-C C# VB.NET UWP Delphi Python Java Android LabVIEW
API / SDK / Libraries (TCP only):Javascript Node.js PHP
RoHS compliance:RoHS III (2011/65/UE+2015/863)
Suggested enclosure:YoctoBox-Short-Thick-Black
Harmonized tariff code:9032.9000
Made in:Switzerland

1 These specifications are for the current hardware revision. Specifications for earlier revisions may differ.
2 The extended temperature range is defined based on components specifications and has been tested during a limited duration (1h). When using the device in harsh environments for a long period of time, we strongly advise to run extensive tests before going to production.

Accessories and related products

YoctoBox-Short-Thick-Black, Enclosure for Yoctopuce device (short, thick, black)Micro-USB-Hub-V2, Micro USB hub (multi-TT) with solder pads, for DIY useFix-2.5mm, screws and spacersUSB-A-MicroB-50, USB 2.0 type A to Micro-B data cable, 50 cm

Related articles and application examples


User manual (HTML)
User manual (PDF)
Product brief
3D file (STEP)
RoHS certificate
Most recent firmware51180 (12/02/2022)
Programming libraries61305 (06/11/2024)
Command line API61199 (05/30/2024)
VirtualHub application61458 (06/14/2024)

Add a comment 13 comments

1 - pulcherior Monday,december 01,2014 1H20


My goal is to be able to programatically control external hard disk (power on/off).
The drive has 1 usb cable and a power adapter.
Is this possible? If so, what type will be appropriate, Yocto-Relay or Yocto-PowerRelay?


2 - martinm (Yocto-Team)Monday,december 01,2014 8H25

If you only want to be able to cut the disk power, a Yocto-PowerRelay will be fine*. However you'll have to check in the disk documentation if you are allowed to keep it connected to USB when not powered.
(*) since your power adapter is probably an inductive load, protecting the relay with a TVS diode might be a good idea, check the Yocto-PowerRelay doc for more info about use with inductive loads.

3 - youngsub Thursday,november 19,2015 16H51

I tried using Python and it works perfect. But when I tried with C++ code, relay works only first time and after that it does not work without any error message.

4 - mvuilleu (Yocto-Team)Thursday,november 19,2015 17H51

Feel free to contact support@yoctopuce.com and send us your code so that we can help you to fix it.
The C++ lib should definitely work as well as the Python version...

5 - youngsub Thursday,november 19,2015 23H18

I compiled cpp sample code downloaded from this site using Visual Studio 2012 and ran "VisualStudio.exe any 1 A[or B]" on command line.

6 - martinm (Yocto-Team)Friday,november 20,2015 5H41

Actually, you are supposed to type:

VisualStudio.exe any A[or B]


VisualStudio.exe any 1 A[or B]

7 - youngsub Friday,november 20,2015 17H25

You are right.
Now it works. Thank you.
It is different from the way Python program is implemented.
In such case I need to make some change in the code since I have dual relay and I want to use both independently.
I think I can make change in the code to support that.
Thank you for your help.
It is amazing product anyway.
Awesome design and complete package of software support.

8 - yellow_jacket Tuesday,march 29,2016 22H21

I'm retired but used to write a small amount of C++ at work where I had access to a compiler. Now I have no compiler but I would like to control the relay with my computer via USB. But rather than simple switching, I would like to have code to randomly switch back and forth with operator set limits on time. Could you provide this code since I can't compile anymore?

9 - seb (Yocto-Team)Wednesday,march 30,2016 7H37

@yellow_jacket : There is free C++ compiler on each platform: on Linux you can use gcc, on OS X
you can use Xcode and on Windows there is a free version of Visual Studio (Visual Studio Community).

10 - webjoy Monday,july 04,2016 15H11

Is it possible to catch the relay state, if it changes with


11 - martinm (Yocto-Team)Monday,july 04,2016 15H14

@webjoy: yes with relay.get_State(). You can even set a callback on state change with relay.registerValueCallback().

12 - eduarte Saturday,september 01,2018 4H12

I have bus ticketing app on android which activates turnstile via bluetooth.

I am having trouble with stability so i am looking for a wired alternative.

Can i code and control yocto-relay into my app and make it flash the relay?

Mind you this would go on about 600 - 1000 times a day.

13 - martinm (Yocto-Team)Saturday,september 01,2018 6H19

For such a high switching frequency, electro-magnetic relays might not be the best answer. Contact Yoctopuce support.

Yoctopuce, get your stuff connected.