Dynomotion

Group: DynoMotion Message: 9532 From: embracedm6 Date: 5/25/2014
Subject: Certain USB cables causing erratic behaviour

Hi all,


I'm getting some very strange behaviour with my KFlop. 


Whenever I turn my stepper's PSU on (48VDC) it causes the KFlop to lock up. Kmotion and Mach3 both freeze, and return to normal upon removing the USB cable and switching the PSU off. I have another power supply to power the KFlop which does not cause the same issue. 


I had believed it was a ground loop problem, so I isolated the KFlop's ground connection. This did not solve the problem. 

I then changed the USB cable for the one that was supplied with the KFlop, and this fixed the problem. However, with my setup this means I have to leave the enclosure door open the entire time I run the machine, as the USB cable must exit the enclosure. I would like to use a panel mount USB socket to solve this - but the one I have causes the same problem mentioned before.


My questions are these: - Why am I getting erratic behaviour

    - Is this erratic behaviour likely a ground loop

    - Why does the supplied USB cable fix the problems

    - Is there a panel mount USB socket that could be used in my setup



Thank you.



Lindsay
Group: DynoMotion Message: 9533 From: tmday7 Date: 5/25/2014
Subject: Re: Certain USB cables causing erratic behaviour
Can you remove your panel mount socket from enclosure and dont let it touch anything and see if problem is still there.

HTH,
Troy
Group: DynoMotion Message: 9537 From: Tom Kerekes Date: 5/26/2014
Subject: Re: Certain USB cables causing erratic behaviour
Hi Lindsay,

As Troy mentioned many of the USB Panel Mount Inlet Connectors connect the Shield to the panel.  This can couple earth ground noise into the USB cable shield and in turn into the USB signals, DC GND, and Power lines.  It may also form ground loops.  Check with an ohm meter if this is the case.  Try isolating the mount if possible.

Regards
TK