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Old Thu 18 June 2009, 05:46
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
Heard today that the Smoothstepper is not going that smoothly, it sometimes looses comms with the computer. Was told by Greg Cary a few months back:

"If you have any trouble with USB communications dropping out, many have found success by adding a good ground wire between the computer and the SS (in parallel with the USB cable). Another option is to treat the SS as a parallel port and keep it close to the computer, connecting the SS to the breakout board via a parallel port cable (and not use a ribbon cable). In that case you would want to use as short of a USB cable as possible in order to minimize its exposure to noisy electrical signals. I only mention these things in case you have any trouble. Most people don't have any issues, but a few do. I'm certain that most of the issues are ground loop related. A good star ground is essential for any system."

Also found this on another forum

"I am not certain of the solution, though I have strong feelings that it
is a ground loop problem. I think that the loop is formed like this:

ground of the PC -> USB cable -> SS -> ground at the SS -> ground
through the system -> ground of the PC.

There are a number of things you can try. Some of them are cheap, and
some expensive. In the warp9td forum, someone said they had success
with running the SS with a laptop which was powered by batteries. Then
they tried the desktop computer without the earth ground connected.
Disconnecting the earth ground is not something I recommend because of
safety reasons, but in this person's experiment, it fixed the problem
(which was the communications getting killed when the spindle turned on
(I think)). What it tells me is that there is a ground loop that must
be broken. An expensive solution is to purchase an isolated USB
interface. Here is a link to a company that sells such a link:

It looks like they have distributors worldwide:

I was just looking at the website of one of the distributors, and I
found the following (

Here's a hardware design tip that is the coming thing ...

* Input Power: If your product is aimed at the international as well as
domestic markets, especially for mobile operation, use a power supply
"brick" that will work from 100 to 240 VAC, 50 to 60 Hertz and is of the
"two blade" variety (isolated, no ground prong). This helps during
"brown outs" and power surges and is easy to use overseas without
inverters. These "universal" or "international" power supplies can work
just about anywhere in the "first and second world" and most of the
"third world". This will save a significant number of support phone
calls and requests for unprofitable, optional supplies. Don't reinvent
the wheel here ... it will increase inventory costs, tech support and
sales grief later.

* Output Power: If possible, make the output voltage from the power
supply brick 11 to 14 VDC, and less than 500 milliamps. This will match
the power from 12 VDC, auto, truck and solar power adapters. This makes
your gadget "mobile". You may have add DC regulation on your circuit
board to accommodate this, although many USB and FireWire 1394 chip sets
have this on board regulation.

Interesting that they recommend an isolated supply

Another potential solution is to minimize the voltage drop from the PC
to the SS. Adding a heavy ground from the PC to the SS will help. My
suspicion is that the ground loop stills exists, but it doesn't matter
if there is a current flowing through the ground if the impedance from
the PC to the SS is very low. Voltage drop across the cable is equal to
the current times the impedance (resistance). Minimize the impedance
and the voltage drop decreases the same amount. Unfortunately, USB is
not a purely differential signaling standard. There is a part of the
protocol that references the signals to ground. That is too bad, and is
probably the reason why this is happening. Adding a heavy ground wire
in parallel with the USB cable (power supply ground from a hard drive
connector, connected to the SS's ground) might help matters.

Some people have reported good success with using a USB host adapter
with a chip from NEC. I guess all USB interfaces are not equal, and NEC
has done a good job of implementing USB. Here is a link to a company
that advertises a cable that uses an NEC chip:

I believe that an extension cable such as this is really just a USB hub
chip with only one downstream port. You might be able to solve the
disconnect problem by putting a self-powered USB hub in between the SS
and the PC. Others have found a lot of success doing that. Others have
found success disabling the computer's ability to disable a USB port to
save power. Is there any chance it could be that the computer is
turning off the power to the USB in order to save power? You can turn
this feature off if that is the problem. Some users in the Mach Yahoo
Group have found this to help:

The following instructions are for XP. If you go into Device Manager
(Start -> Run -> devmgmt.msc), you will see "Universal Serial Bus
Controllers". Once Device Manager is open, look near the bottom for
"Universal Serial Bus Controllers". Expanding this will reveal a number
of "USB Root Hub" items to select from. If you select one and
right-click on it, you will have the option of "Properties". When you do
this, a dialog will pop up with 5 tabs. One of them is "Power
Management". Selecting this reveals an option that says "Allow the
computer to turn off this device to save power". De-select this. I
noticed there is another tab named "Power". Selecting this tab may help
in identifying which USB connector is associated with which Root Hub. I
plugged a Microsoft Mouse into each port to help determine which one was
which. You might want to allow some of the root hubs to be able to turn
off the power.

Another possible solution is to remove the capacitor and the resistor
right next to the USB connector, opposite the side with the LEDs. The
reference designators are "C4" and "R5". These connect the cable shield
to the ground of the SS. I have one report of this fixing the problem,
and one report that it did not. Shields should only be connected at one
end. Typically this is done at the signal source. In the case of USB
it is bidirectional, so both ends are the source and the destination.
So I think the host side is usually the end that is grounded. The SS
side is not a direct ground. AC transient signals can pass through the
capacitor to ground, while not providing a DC connection. The resistor
is in parallel with the capacitor, but the value is 10 MegaOhms, which
is very high. Basically its intended purpose was to bleed DC charge
away over time. Kind of like a lightning rod. I found this circuit on
a website when I was designing the board. Most reference designs that I
saw did not have such a circuit, and I am questioning whether or not
they are doing more harm than good. If you removed these components, I
don't think you would be hurting the SS. In fact you would be making
the design similar to the majority of USB designs out there. Or you
find success by adding another capacitor across the existing one. Noise
is black magic.

Please let me know if this does not help. I feel that if you think very
hard about where the currents are flowing, you will find that you do not
have a "star ground". You do not want ground loops. Ground should be
located at a single point and radiate out like a star."
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Old Thu 18 June 2009, 06:17
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
Reading of Panaceabeachbum's problems from here, only a few days ago, is getting me nervous . . .

He solved it by moving the SS to the PC cabinet, short USB cable internal to the PC, and then a "conventional" DB25 cable to the BOB board in the control cabinet.
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Old Thu 18 June 2009, 11:28
Just call me: Sean - #5, 28, 58 and others
Orlando, Florida
United States of America
shielding issue maybe?
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Old Fri 19 June 2009, 07:17
Robert M
Just call me: Robert
Lac-Brome, Qc
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Im not even at the kitchen project yet, (but soon to be) and this SS starting to worry me !
I bought one last year as part of some materiel for the MM project of which I was hoping to finish by end of last yr.
With this info you're giving us here, I now know, when my "D-day" comes, I will not have it as some initial parts for the beginning runs, minimizing risk and potential hard to find troubles !
BTW, would I remember right that you where too waiting to get one as you where then on their shipping waiting list ?
Did you finally get one or did you dropped the thought and never purchased one?
If you got one, how is it stepping for you ??
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Old Fri 19 June 2009, 10:28
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
Robert. my son has about 4 or 5 Smoothsteppers and his friend Jordan is setting up the first one. (I am personally staying away from them because they have to learn how to do it). This thread was started because Jordan discovered the communication problem here in Cape Town. I then looked at more forums and discovered that this is a common problem.

It seems the best solution is to mount the SS inside the PC, our very close outside the PC, keeping the USB cable very short. And then run an old-fashioned printer cable from the SS to the control box. I must say that this is an ugly solution and I was hoping for something more elegant.
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Old Fri 19 June 2009, 12:36
Robert M
Just call me: Robert
Lac-Brome, Qc
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Will use your advice when time comes...But only well after the MM runs !!
BTW, If I remember correctly, someone wrote once; solutions arent meant to be elegant, but functional & /or efficient
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Old Sun 09 August 2009, 09:11
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
Matt is also having these problems with the SS (link)

My son mostly resolved his problems with wiring changes, but we are not 100% convinced it is all clear now.
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Old Sat 05 September 2009, 10:58
Robert M
Just call me: Robert
Lac-Brome, Qc
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Gerald, may I ask you to give some update on your son connection w/smoothstepper.
As you noticed from other posts I did today, Im in my final stage for my electrical schematic and then do some purchasing, and this would help me (& surly other too ) to consider having the computer V-close to the control box ( BOB) if a smoothstepper is consider !
Or better yet ... Should we just not use it ?!...but that is another debate & topic by its self
Merci, Robert
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Old Sat 05 September 2009, 11:39
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
Our SS is working now (shortened the USB cable and moved it away from noise sources), but it needs longer testing to see if it is really worth it.
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Old Mon 14 September 2009, 15:20
Robert M
Just call me: Robert
Lac-Brome, Qc
Send a message via Yahoo to Robert M Send a message via Skype™ to Robert M
Hi Gerald,
Hate to ask some more about this SS situation , but since Im in the electrical drawing & planning to get my kitchen project ready....the possible misshape or not set it up right, preoccupies me ALOT !!!
Im a little bit confused on the wiring situation for the SS
In post 5, you say Ugly solution !
My questions or need for clarifications are :
must say that this is an ugly solution and I was hoping for something more elegant.
- What do you find UGLY? .Cause to me, when you express something like this, I assumed it has nothing to do at what it actually looks like but more about the technical aspect of it .or does it ?

Im planning to have the control box in a close proximity with the computer, either side by side, a few inch apart or one above the other, distanced again by only a few inches.
As for this SS wiring solution, would you recommend me to use a ribbon cable directly from the SS board inside my computer directed directly to the PMDX inside the controller box, no female & male connection between ?
OR....would you recommend using a ribbon cable from again the inside of the computer but with a DB25 female connector at one end Would be as OK
(Like this one)

then from there, using a regular printer cable directly in the controller box to the PMDX. Cable through the controller box casing only with a cord grip. This last one is a suggestion to minimize male / female connections?!
Thanks again for your help !
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Old Mon 14 September 2009, 21:59
Gerald D
Just call me: Gerald (retired)
Cape Town
South Africa
I like a cable to be firmly anchored where it enters/leaves a box. This is so that cheap labour can be given a broom and told to clean the workshop floors/walls without any risk of killing a machine. The external cable must also be strong - a ribbon cable is weak, USB and old printer cables are strong.
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Old Mon 19 September 2011, 17:16
Just call me: Donna #87
Suwanee, Georgia
United States of America
Can Smothstepper connect to VFD and mach3

I was wondering if the smoothstepper can also be used to control the speed of the spindal and if so how does it connect to the VFD.
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Old Tue 20 September 2011, 02:15
Just call me: Danilo #64
Novi Sad
Easiest way of mach3 spindle control if you have modbus enabled VFD
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