Messages

21

SmoothStepper USB / Re: If you have noise issues this might be worth a try

« on: November 08, 2010, 03:13:48 PM »

Thanks Hood and Jeff for sharing your findings and solutions.  Jeff's solution of cutting the trace is a fine one.  Just beware that the ground plane is close to the surface (about 0.0073 inches below), and that if you cut into it there is a chance that you could short the outer trace to the ground plane and you won't accomplish anything.  I don't want to make it sound like cutting the trace is risky, but I just want to point out something you might not be aware of.  Like Jeff suggests, use an ohm meter to make sure the connection has been severed.  To see if the shield was accidentally connected to the ground plane, ohm from the outer shell of the USB connector to the ground of the board.  You can find ground on the external 5V connector or pin 5 of port 3 (green screw terminals).  The distance from the ground plane to the power plane is huge, so there is no worry about shorting the ground plane to the power plane unless you really dig deep!  The distance is about 0.039 inches.

For those of you that would prefer to desolder the components, I took a before and after shot of that area of the board:

Before:



After:


Thanks,

Greg

22

SmoothStepper USB / Re: SS-C23 problems

« on: November 08, 2010, 02:48:28 PM »

Maybe the problem is that Mach doesn't allow the plugin to be updated when you are in motor tuning.  Unfortunately the only thing you can do at this time is to make the changes, exit Motor Tuning and then they will take effect.  I hope this changes in Mach4.

Thanks,

Greg

23

SmoothStepper USB / Re: SmoothStepper died

« on: October 08, 2010, 11:55:45 PM »

Jeff, Thanks for that excellent explanation.  I agree with everything except I'm not sure about the 100 mA limit.  I believe the USB port will typically put out more than that and the current limit doesn't go into effect until about 1 amp or so.  Under high load the voltage droops considerably like you mentioned.  All devices start out at 100 mA or less.  After configuration they can bump up to 500 mA if they are a high-power device.  I just experimented with the USB port on my development computer.  I placed a 6-ohm resistor from Port 3 pin 4 (5V) to ground.  I then plugged the USB cable into the board and measured a current of about 700 mA through the resistor.  I guess that would equate to a bus voltage of about 4.2V, though I didn't measure that.  The SmoothStepper was recognized by the OS without a problem.  I think the only reason for keeping track of the current is so that the OS can decide if a device will draw too much total power from all of the USB ports combined.  If a high-power device is plugged in, the OS would be able to deny it from bumping up to a higher current.  The concern is the risk of loading down the bus and having a bunch of USB devices drop out from the low voltage.  There is also a spec that limits a device to 10uF of capacitance for a similar reason.  Too much capacitance will suck a ton a current for a brief moment when the device is plugged in, which could reset other USB devices connected to the computer.  I made sure the SS conformed to that spec.  There is a 100uF cap on the board, but it is only on the external 5V input.  One other point is that a device doesn't even need to enumerate to draw power from a port.  You can draw more than 500 mA from a port and not even be a USB device.  Of course every USB host is different.  Some could have current limiting at various levels, but I think most have one level set a bit higher than 500 mA.  For what it is worth, I did a web search and found this interesting site that shows some data that a guy compiled on various devices and how the voltage drooped at low and high current levels.  I didn't study it much, but here it is:  http://www.girr.org/mac_stuff/usb_stuff.html

Maddios, Those voltages are very suspicious.  I am wondering if your voltmeter is that inaccurate or if you are measuring from a ground that is not the ground of the SS.  I am hoping that you are connecting to the ground of the computer or something like that.  If so, that would indicate that the ground of the SS and the ground of the PC are not at the same voltage.

It is interesting that you can see a temperature difference in that one chip.  I have a feeling that the board will need to be replaced, but I want to spend more time working through this so that if a new board is installed something bad won't happen to it because of some mis-wiring or something like that.

Thanks for taking the time to take those measurements.

Greg

24

SmoothStepper USB / Re: SmoothStepper died

« on: October 08, 2010, 07:25:47 PM »

It sounds more like your meter is off.  It would be very unlikely to have multiple regulators read 0.2V high.  It will be interesting to see if you read a different set of voltages with a different meter.

I think you hit it on the head with the reason for the external 5V supply.  Although besides the higher current availability, some people have had better luck with a more stable SS system using the external 5V than the USB supply.  I think some USB ports do not output a very strong 5V, particularly laptops.  I also think it might have been more of a problem in the past though.  I personally haven't ever had a problem with the USB's 5V supply.

As for grounding, I think it is hard to define the center of the star in a star ground when using a USB device.  Should the PC be considered the center?  Or in this case the SmoothStepper?  I think that is why better USB cables help a lot because they have heavier gauge wires for power and ground.  Short cables help a lot too.  I think it is important to keep the ground of the SS and the ground of the PC at the same potential.  I would like to hear Jeff's opinion on this.  I consider him the noise and grounding expert!  I do believe it is important to keep the ground of the PC and the ground of the SmoothStepper tied together as tight as possible.  You don't want a ground loop that involves the cable.  If the PC's ground is different than the SS's, then a current will flow.  Jeff, any thoughts?

Thanks,

Greg

25

SmoothStepper USB / Re: SmoothStepper died

« on: October 08, 2010, 05:25:12 PM »

Glad the SS has made an improvement to your system.  Hopefully you'll be back in operation soon.  Sounds like there is a problem with one of the power supplies on the board, and it probably isn't 3.3V.  The FPGA (large chip in the middle) requires 1.2V, 2.5V, and 3.3V.  5V goes to all of the interface chips (like the ones near Port 2).  The USB chip is powered by 3.3V, so it is unlikely that 3.3V is in trouble.  It could be an unrelated problem that the chip near port 2 is bad, or it could be that the external 5V from the ATX power supply went over-voltage like Jeff mentioned.  They usually do require a minimum load to regulate.  On the board you will see "1.2V", "2.5V", and "3.3V" in the silkscreen.  You should be able to measure those voltages.  If none of them are above a certain threshold, then the FPGA will not allow itself to be configured.  When it is properly configured, the red LED will go out and the green one will light.  The fact that it can't communicate with the CryptoMemory is that the FPGA is not working.

Please let me know what you see when you measure those voltages.  Hopefully you will find something that is causing it.  If not I will exchange it for a new one.

Greg

26

CVI MachStdMill (MSM) / Re: G73/G83

« on: September 15, 2010, 11:23:14 PM »

It sure sounds like a syncing problem to me.  The SS tells Mach it is still and what the current position is.  Mach calculates the next move, but it must be using the wrong positions.  I am going to ask Brian to help figure this out because I haven't changed anything in that area of the code.  I suspect it is a timing issue.

I'll let you know what I find out.

Greg

27

General Mach Discussion / Re: Problems threading on the lathe

« on: May 26, 2009, 02:25:35 AM »

Hi Richard,

Sorry to hear about all of the trouble you've been having.  It is strange how USB works flawlessly for some and not for others.  Thanks Hood for your determination in getting to the bottom of this one.

I would guess that you would have the best luck shortening the USB cable as short as you can (6 inches if possible), and then using parallel port cables to go from the SS to the breakout boards.  I can't guarantee it, but I have had users fix USB communications problems that way.  Another possibility is to run a heavy duty ground wire between the SmoothStepper and the computer, in parallel with the USB cable.  I suspect you might have a ground loop present, and while it would be best to eliminate the ground loop, you can minimize it by minimizing the impedance between the computer and the SS.  Another trick that can help is to insert a self-powered hub in between the computer and the SS.  A hub can help regenerate the USB signals and interfere with the ground loop.  It would be interesting to see if you can measure any voltage difference between the ground of the SS and the ground of the PC.  You can also try plugging things into different outlets.  Please let me know if any of this helps.  If it doesn't we'll keep at it.

Thanks,

Greg

28

SmoothStepper USB / Re:SS DISCONNECT SAFETY CONCERNS

« on: December 10, 2008, 01:45:37 AM »

Hi all,

I have replied to this in the Warp9TD forum.  It is a problem that I will address tomorrow.  If the SS loses communications with the PC it should stop jogging, but it doesn't.  Even if it doesn't lose communications, the current implementation could be a problem if a jog-off command were swallowed.  Motion from gcode and step jogs will stop as soon as the SS runs out of data, but continuous jog movement is generated on-board.

Thanks,

Greg

29

SmoothStepper USB / Re: PWM output for spindle

« on: November 16, 2008, 12:08:09 AM »

Hi Repmo,

It always makes me happy when I see that someone has a scope!

Let me describe the parameters you need to set.  Maybe one of the following things is not right in your configuration.  I should have a section on this in the manual.  I think the spindle software needs some attention, so I will update the manual as soon as I get that cleared up.

First start with Mach's Ports & Pins config.

Select the Motor Outputs tab.

• Enable the spindle
• Assign port numbers
• Assign pin numbers

Select the Spindle setup tab.

• Check the box that says "Use Spindle Motor Output"
• The other check and edit boxes do not apply to the SmoothStepper.

Motor Tuning

For PWM it is a little different than Step & Direction.  This software needs to be cleaned up in the SS.  For now, please follow these directions because they will work:

For PWM:

• Set "Steps Per" to 1000 (you can adjust this later to adjust the acceleration)
• Set "Velocity" to 60 (This only has an effect on some calculations Mach does.  It has no effect on the actual output from the SS)
• Set "Accel" to 1 (The accel is calculated as "Steps Per" * "Accel", so just adjust "Steps Per" to get the accel results that work well)

For Step & Direction:

• Set "Steps Per" to the maximum step frequency.  This is the frequency that will produce the maximum speed of the spindle motor.
• Set "Velocity" to 60.  This is a magic number that allows you to enter the max step frequency for "Steps Per".
• Set "Accel" to whatever value gives you the acceleration you want.

Config -> Spindle Pulleys

• Select a pulley
• Choose min and max RPM, and a ratio so that spindle feedback calculates the correct RPM for display

SmoothStepper Config (Under PlugIn Control)

For PWM:

• Check the box for PWM
• Select a base frequency for PWM (in Hz)

For Step & Direction:

• Check the box for Step & Direction
• Select a step pulse width.  Make sure the frequency that was selected in Motor Tuning is not too fast for this pulse width.  Otherwise the signal will never transition.  For example, for a max step frequency of 25 kHz, the maximum pulse width is 40 microseconds.  At 25 kHz, the waveform would be 100% duty cycle if the pulse width is 40 us.

Please contact me at support @ warp9td.com if you are still having trouble.  Please let me know which version of the plugin you are using, which version of Mach, and if you provide you XML that will help a lot.

Thanks,

Greg

30

General Mach Discussion / Re: Mach3 Spindle Speed Problem

« on: October 29, 2008, 09:27:45 PM »

Hi Chris and Ray,

I played around with it a little, but I didn't see that happen.  There are a number of variables though, and it would help me if you could e-mail your XML (and screen set if it is different (if you'd like)) to me so that I can run with the same exact parameters as you.  Please send them to me support@warp9td.com if you want me to take a look.

Thanks,

Greg