Maintaining USB connections?

[chuggins143]

This may seem a bit off topic, but how do you guys take care of the physical USB connections?  Ox-guard?  Dielectric grease?  I'm occasionally having my hub drop a connection and if I unplug it and plug it back in all is well.  I'm just thinking a bad connection and should start some preventative maintenance as all of my DAQ hardware is USB driven.

Later,

Chad

[EEsRULEtheWORLD]

Hey Chad,

What is causing your connection to drop?  Are you working in an area with a lot of interference?  Do you have other applications running on your system while acquiring data from your USB device?

[Scott_T]

On a related note:

Our USB-6211 DAQ tends to drop out several times a day. Unplugging and replugging fixes the problem, but it may take a few tries. Our system also has a USB to RS-485 converter and a USB to I2C converter. These two devices never drop out. The only application running is LabWindows/CVI.

Scott T.

[chuggins143]

Hi Sara, I have no clue as to why it drops... it appears to happen randomly.  I'm just figuring it's a possible contact issue.  Since I've coated my contacts with dielectric grease is seems to be happening less frequently.  Although I am starting to think it's hardware related since it only happens with one unit and is doesn't matter which port on the hub I plug it into.  The hardware is a MCC PMD-1208LS DAQ board.  I have several of these units working in my lab and I've never had this issue with any of them.  I'm just trying to cover my bases and make sure it's not something simple before I start hunting for bear. 

THX

Chad

[EEsRULEtheWORLD]

Hi Chad,

You may want to check your power settings to make sure that the USB ports are not being turned off to conserve power.  The USB power save option can be set via the Device Manager (right click on My Computer and go to properties, then on the Hardware tab click Device Manager). From Device Manager expand the Universal Serial Bus controllers entry and for each USB Root Hub entry right click Properties»Power Management and uncheck the Allow the computer to turn off this device to save power option.

[Sean-user]

I used the USB 6211 is a bus powered DAQ. In my experience, these are very susceptible to some unusual problems. If you are generating an analog output signal or some digital output line/port, your current load could easily limit the device and potentially the USB bus powering the device.

Additionally, distances can be a serious problem. USB only supports a few meters. Beyond that, devices begin to malfunction.

I used a 6211 to acquire analog signals. I suspect my reliability issues are due to seperate circuits being used to power areas of it. My sensors were powered by one circuit (circuit A). The USB bus was powered by the computer's circuit (circuit B). This shouldn't be a problem aside from potential noise issues. End-users decided to use a HUB since there were multiple DAQs. These HUBs were powered by circuit A. This could cause serious problems especially as new loads are introduced on A (like the heaters that turned on and off to regulate temperature). Also many hubs have poor quality.

I am already a fan of the ethernet based DAQ systems. I haven't put them through the wringer yet, but the TX and RX differential pairs should offer better isolation (compared to USB's fullduplex differential pair and the 5V and GND lines).