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[Plugin] Extra Outputs HID USB Relay.

41 Posts
6 Users
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Posts: 71

I have built a unit using the USB board. I am using the software plug-in to operate the relays. 

Rather than rely on the small on-board relays, I am using the board relays to switch mains-rated, heavy duty relays (to operate fans, etc).

However, I am finding the USB communication is very tenuous - it drops out all the time on the bench.

I thought maybe the switching on of a relay was pulling down the power supply momentarily and so I added a big capacitor to the power supply, but drop outs still occur - often when a relay is disengaging. To make the board work again means restarting YourDyno.

Any ideas?

Posted : 14/02/2019 9:26 am
Posts: 362
Dyno Wizard
Topic starter

Which board specifically did u get? How long is the USB cord? Is there dieode to stop flyback?

Can do some trouble shooting with code tomorrow night. Haven't had a single issue with the board I'm using.

Posted : 14/02/2019 9:36 am
Posts: 71

The board is the one you nominated - via eBay.

USB cord is 1.5 metres long.

No flyback diodes needed when using relays to trigger relays. 

Posted : 14/02/2019 9:40 am
Posts: 362
Dyno Wizard
Topic starter

Have attached the offical software that came with the relay board (well my 8 channel one).
Give that a go and see if its showing the same issues, Then ill know if its my plugins code thats the issue or hardware wise.
Im using the 2 channel one from that seller on a project at home for my water chiller on my PC.
At work on the dyno Im using a 8 channel one that I got from a local supplier. Blue board with micro USB plug but everything else looks the same as there pictures.
Im using a 0.5M USB cord since everything is inside the cabnet the PC is ontop of. And using the relays directly.

Posted : 15/02/2019 5:41 am
Posts: 71

Thanks for that - it's not your software because it does it with the 'official' software as well. 

When you were testing, did you have the board powered up with the 12V supply as well as the USB 5V supply (via the cable)?

I just tried every 12V power supply configuration imaginable, and communication drops out with all of them. (The official software then reconnects, though.) 


Posted : 15/02/2019 6:40 am
Posts: 362
Dyno Wizard
Topic starter

12V taken from PC molex plug. (yellow wire) and earthed back to PC molex (black wire)
Here is what it says in the support html file that came with my 8 channel one.
I got no cd or paper work from that ebay seller that I got the 2 channel one from. But everything worked exactly the same on it so thought nothing of it.

Loss of Communications with the USB Relay Board

The High Voltage Spikes released by inductive loads are NOT compatible with USB communications.  Frequently, these spikes will travel through the USB port directly back to your computer, causing your motherboard to disconnect the USB device from the list of available USB devices.  The only way to recover from this condition is to remove the USB device from the computer and plug it back in.  In extreme cases, the inductive spikes can cause damage to the USB port of your computer.

It’s easy to blame a controller for malfunctioning when working with inductive loads, but in reality, the fact that a controller (regardless of manufacturer) malfunctions when working with these loads does have one benefit:

A malfunctioning USB relay controller is a sure way to indicate to the user that something is terribly wrong with the installation, and it must be properly handled to ensure a long life span.  Inductive loads MUST be managed externally, away from the relay board, regardless of how good your controller is.  We put together a tutorial on Controlling Inductive Devices which demonstrates the problem.  Inductive loads are typically managed using external components, as shown in the tutorial.  When a controller malfunctions, it’s letting you know the problem has not been properly managed.  When a controller is working properly, induction is properly managed, and the relay controller can give you years of reliable service.  Unmanaged problems can lead to early failure of the relay controller and potentially damage to a computer.  The USB port is a fragile bus, and the fact that it kicks off devices that misbehave is an ideal way to protect the computer from the serious electronic damage that can be caused by induction.

In our USB relay boards, we galvanically separate the USB circuit from the relay control PCB.  This provides greater noise immunity on the USB port, allowing the controller to tolerate a little more induction before your motherboard kicks the device off the USB bus.  Extreme induction will still cause our controllers to malfunction, but this is easily managed with an external components.  Properly suppressing induction requires external components to be installed as close to the inductive source as possible, which is why it is not possible for us to include these components on any of our relay controllers.

Symptoms of Unmanaged Inductive Loads Include:

  • USB Driver Disappears from the Device List of your Computer

  • Software will Unexpectedly Crash because the USB Port Has Been Terminated

  • The USB LED will Turn Off on the USB Relay Board

  • Activating or Deactivating a Relay Causes All Relays to Turn Off

  • User must Physically Remove the USB Plug and Re-Insert to Resume Operation

  • Controller Becomes Unreliable or Loses Communications

  • Extreme Cases may Damage the USB Port of your Computer

Then lower down has a note that says

When the inductive load is a relay, the flyback diode can noticeably delay the release of the relay by keeping the coil current flowing longer. A resistor in series with the diode will make the circulating current decay faster at the drawback of an increased reverse voltage. A zener diode in series but with reverse polarity with regard to the flyback diode has the same properties, albeit with a fixed reverse voltage increase. Both the transistor voltages and the resistor or zener diode power ratings should be checked in this case.

Posted : 15/02/2019 6:58 am
Posts: 71

Thanks for all that. I've now tried flyback diodes across the external relay coils - no change. 

Sorry, but I can't afford to spend any more time on this. I am going to a four-channel remote control that can easily replace the USB board in the box I am using. 

Thanks for your input. 

Posted : 15/02/2019 7:13 am
Posts: 362
Dyno Wizard
Topic starter

No worries, Sorry I couldnt be of more help and provided a link to a dud usb controller.
Have added a warning note to first page.

Posted : 15/02/2019 7:51 am
Posts: 36
Posted by: @bmgjet

Plugin for USB Relay.
by bmgjet 2019


Provides automatic control based on dyno input.


[V1.0] Plugin Library
[V1.1] [Still in Alpha] Visit last post for latest alpha build.


Hi @bmgjet

Did you ever release v1.1 of this relay plugin?

I've had a look around and cannot find the alpha version in the 'last post'.

Thanks for your help! 

Posted : 04/10/2021 9:37 pm
Posts: 24
Member Customer



I bought the 2 relay board some times ago. I installed it in the dyno, but it was my understanding that I could operate the realys while using the dyno (for the rapid operation of fans and extraction).

I can't achieve that: I am not able to define an hotkey for this for example. with the relay page opened, I can control relays but I can't open the retardation page in the meanwhile.


Is there a way to do so?


V1.1 installed with yourdyno installer



Posted : 27/12/2021 9:49 am
Posts: 1230
Member Admin

@matteozanusso, the KMTronic relay can be controlled by other channels. Hotkeys are not available for the relays, but I agree this is a good additional feature. 

Posted : 27/12/2021 11:17 pm
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