Dynomotion

Group: DynoMotion Message: 11331 From: jb10425 Date: 4/9/2015
Subject: Lost USB connection to KFlop/KStep

I had a problem with my CNC machine that uses KFlop/KStep boards.


The CNC router stopped in the middle of a run. The computer to CNC connection was lost.


Several minutes before the disconnection, I got a static shock when I touched my dust collection hose. I think this might have been just a coincidence since the lost connection did not happen right away, but I don’t really know.


Here is the state of the system when I turn on power:


  • KStep LEDs: D1 on, D2 blinking, D3 off

  • KFlop LEDs: D1 off, D2 off

  • The computer does not see the USB connection (KMotionCNC displays a "No KMotion devices available" message)


If I disconnect the KFlop to KStep ribbon cable and turn on power:


  • KStop LEDs: D1 on, D2 off D3 off

  • KFlop LEDs: D1 on, D2 on

  • The computer sees the USB connection and KMotionCNC runs normally



John
Group: DynoMotion Message: 11346 From: Tom Kerekes Date: 4/10/2015
Subject: Re: Lost USB connection to KFlop/KStep
Hi John,

Sorry to hear you are having problems.

It sounds like KStep is damaged and some how loading down KFLOP in some manner so it can't boot.

It seems strange that KSTEP D2 (+5V) would be blinking.  That would indicate the +5V supply was turning on and off.  Possibly a bad supply or something with KStep drawing a large amount of current for some reason.

I assume you are running in non-isolated mode where KStep +5V power is being obtaind from KFLOP +5V?  You might try removing Jumpers J34 and J35 so KStep doesn't obtain +5V or GND from KFLOP to see if KFLOP can then boot normally while the two boards are connected together.  Also if applying +5V to KStep by itself draws an abnormally high current.

Regards
TK


Group: DynoMotion Message: 11357 From: jb10425 Date: 4/11/2015
Subject: Re: Lost USB connection to KFlop/KStep
Hi Tom,

Thanks for your reply.

I think your suggestion that KSTEP might be drawing too much current is correct.

I removed the J34 an J35 jumpers and connected the +5V power to the KSTEP (not connected to KFLOP) and the D2 LED blinks. In addition, the LED on the +5V power supply blinks. (By itself, the power supply looks OK.)

I don't have and easy way to measure the current, but there seems to be a problem on the KSTEP board.

Previously I down played the role of the static shock I received, but on reflection I think that may have been the cause for the failure.

 - It was a large static shock--it almost felt like the shock from 120V current.

 - It occurred to me that the several second delay between the shock and CNC stop might have been the time it took to empty a buffer.

In any case, I ordered a KSTEP replacement Friday and I'll see if that fixes the problem.

I've grounded the dust collection hose and ran a ground wire to the frame of the CNC in the hope that this doesn't happen again.


John
Group: DynoMotion Message: 11381 From: jb10425 Date: 4/14/2015
Subject: Re: Lost USB connection to KFlop/KStep
Found the problem--nothing to do with KFLOP/KSTEP boards.

There was a short in the power supply line to my cooling fan/water pump. The short must have caused too much current draw from the power supplies for the KFLOP/KSTEP boards.

John