USB-6009 DAQ random suspension when used via a USB hub

[Sid05]

I have a prototype that uses the USB 6009 for Analog and Digital I/O for controlling a dc motor and solenoid valve through a relay board and a Labview VI. It all works great.

However, I also have some 2 sensors that have their own USB connectors. So, I have to use a USB-hub to allow these 3 USB-based devices to operate in parallel. This is where I start seeing problems. Every few hours or so, the DAQ goes into suspend mode and stops communicating [indicated by the onboard LED not blinking]. My only recourse at that point is to reset the DAQ using NI Max. It resumes operation after that but only to suspend again in some time. 

The DAQ suspend problem occurs more often when I use a Windows Tablet as opposed to a Windows Laptop. The Tablet or Laptop remains powered on all the time - so this is not because of loss of power. And the problem occurs equally as often when I use an externally 5V DC powered USB-hub. 

Is there any solution? Thank you all for your help/guidance. 

[ZYOng]

See USB Device Disconnects and Reconnects Periodically on Windows PC and Using USB Based DAQ Devices on a Bus-Powered Hub

[santo_13]

If you're using a cheap self-powered hub, have you ensured that all three devices + hub can safely operate within power limits from one USB port?

For USB 2.0, you can draw only 500mA @ 5V per port.

Check your windows power settings to not power down USB devices when not it use.

[Sid05]

Thanks for that, Santhosh. I use the Sabrent USB 3.0 hub which can also be externally powered. And no, the computer sleep setting has been disabled - so pretty sure that is not the reason. And my VI runs continously in an automated mode. The suspend has almost always happens when the pump is running at  certain speed [DAQ AO > 0.1V], as opposed to a baseline very slow speed [~0.01V]. 

Cost is not a concern - what would be a high quality hub? 

[santo_13]

Please share your full connection diagram; it looks like the back emf signal or noise when the motor runs are disrupting your USB devices. When controlling mains-powered equipment, especially inductive loads, you must shield and isolate the control system well to keep it stable.

[Sid05]

Hi Santhosh - Please see attached wiring diagram I have tried to draw up. Hope this makes sense. I have also attached the pump driver spec sheet. I greatly appreciate your help with this and further insight on resolving this issue. How does one resolve the back emf issue if that is reason behind this odd DAQ suspend behavior? Indeed the problem only occurs when the pump runs at a non-zero AO from the DAQ - but that only happens when I am using the USB hub with 2 other active USB connections [so, 3 in total]. The problem doesn't occur if it is just the DAQ running the pump and relay boards.