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Author Topic: USB Breakout board for Mach3  (Read 45745 times)

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Re: USB Breakout board for Mach3
« Reply #20 on: June 22, 2011, 12:42:17 PM »
A "Tweakie link"?, I'd have one of those with some chip's

Richard.
Re: USB Breakout board for Mach3
« Reply #21 on: June 22, 2011, 03:13:06 PM »
Oh well lets hope the Uni is brave enough to try it as it would be good to see how well it works. Shame the frequency is just 200KHz though.
Hood

Hood do you really think 200KHz is slow? I spoke to the student who built the CNC and he said he has set Mach to about 75KHz. He uses servo motors with Gecko drives, but think that steppers would perform just as fast. I can't remember what feed rate he could get but remember that it was quite fast. I tried to see what the smoothstepper specs are and it seems it is 4MHz but when you look in the documentation it seems there is a mistake/contradiction when you look at the explanation about the buffered time vs speed.

I looked through the other card's manual again and it seems it is is fixed at 200KHz but you can adjust the buffer time and the usb speed is rated at 48Mbs (running directly into the microcontroller - which seems like it is acting as usb to parallel bridge) as opposed to the smoothstepper @12Mbs with a FTDI bridge chip which might be the bottleneck.

PS. There seems to be a forum at: http://cncdiy.forumr.biz/

Best Regards

Offline Hood

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Re: USB Breakout board for Mach3
« Reply #22 on: June 22, 2011, 03:57:31 PM »
The 200KHz is the frequency of the steps and yes for my machines it is too low, for example the Bridgeport I am re-doing at the moment has servos with 2000 counts per rev encoders, thats 8,000 as far as Mach is concerned. Motors will spin at 5000rpm so that is (8,000 x 5,000)/60 = 666.666KHz

I could use electronic gearing in my servo drives but I prefer not to.

Smoothstepper is capable of pulsing at 4MHz.
Hood
Re: USB Breakout board for Mach3
« Reply #23 on: June 23, 2011, 08:14:40 AM »
Hood, how do you use Mach and which servo drives do you use? Mach has a kernel speed limit of 100KHz (as far as I know) and the Geckos have a limit of 250KHz.

Best Regards

Offline Hood

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Re: USB Breakout board for Mach3
« Reply #24 on: June 23, 2011, 08:30:57 AM »
I use the SmoothStepper which has a max of 4MHz pulse rate and Allen Bradley DSD drives which if I recall correctly have a max of 10MHz

Hood

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Re: USB Breakout board for Mach3
« Reply #25 on: June 23, 2011, 08:33:14 AM »
Just looked for Step/Dir its only 2.5MHz for he DSD drives.
Hood
Re: USB Breakout board for Mach3
« Reply #26 on: June 23, 2011, 11:34:23 AM »
So does the kernal speed not affect a USB breakoutboard? I seem to have tracked down the guy who makes the other board. It seems he has done some extensive testing, a few million cycles in Mach3 without problems. He has also made some improvements on the board over the past 2 years or so. It was difficult following everything as it was posted on a chinese forum. I asked Walter from CNCDIY if a faster speed is available as it seems the guy who made it did so for using on an engraver which might not need as a high speed. It would also be nice if he made the source available for those of us adventurous enough to try and modify it. Will see what else I can do.

Best Regards

Offline Hood

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Re: USB Breakout board for Mach3
« Reply #27 on: June 23, 2011, 12:29:16 PM »
The Kernel speed is only for use with the parallel port, external controllers do the pulsing so it depends on the hardware what that will be. I think the DSPMC and KFlop are about the 2MHz range, not sure about the Galil.
There are also the Mesa and Centipede, I think they adhere to the kernel as per parallel port as they use drivers like the Mach pulsing engine. There is however a plugin being done for the Mesa which should allow more frequency.

Hood
Re: USB Breakout board for Mach3
« Reply #28 on: November 23, 2011, 04:42:13 AM »
Hi, i`m new to this forum.
i can see you and others have been looking at the Xulifeng USB board for Mach3, any luck, i have one and have wired up set Mach as the manual but cannot get anything out of it.

I have no problems with mach the way i normally use it, but am looking for an all encompassing board.

BOB--Driver--Motors
Reg
Re: USB Breakout board for Mach3
« Reply #29 on: November 23, 2011, 01:26:33 PM »
Hi,

Yes, they work quite well. Although mine burnt out due to insufficient load.... ???

If you look at the schematic/manual of the board, you will see a DC-DC converter to isolate the 5V supply of the board from the USB port (Black rectangle made by Mornsun). The manual does not state this but the datasheet does - the DC-DC converter does not have short circuit protection and also needs a minimum of 10% (of max) current draw to function properly.

You can connect a LED to the 5V output and ensure it draws 20mA and you're sorted as the max current the DC-DC can supply is 200mA.

Other than that, remember to connect pull-up resistors to all the step/dir outputs as they are open collector type drivers and to have a common ground. The PWM speed output is the same. I used 10Kohm. I have not tested the 8 dedicated outputs or the speed feedback. The nice thing about this setup is that you can use another PSU to feed the step/dir outputs (remember the board can only supply 200mA max so it is best to use another PSU) also keep in mind that the step/dir output drivers can only sink about 15mA (check manual) so adjust your pull-up resistors according to the PSU voltage you use.

Double check the max input voltage of the 16 inputs as they are low voltage/current types and you need to include a series resistor if you want to use say 24V as the input voltage.

If you go to the cncdiy website there is an option where you can register to get access to the manual, which is newer than the other one which I found somewhere. I can try and attach it to a later reply as I do not have it on me. I did not read the whole manual but recall that some things were a little clearer.

Anyways, hope you get it working and welcome to the CNC arena

Best Regards