GearHeads Forum

  Hi everybody.
  Sorry but am a bit new to this. I need a little help with the wiring changing my Chinese 40w Laser to run the cnc57 board as Art had suggested that I do. I finally got one sent here to Australia, what a hassle and expense that was and now am a little stuck. I messaged a few people for help but figure they must be too busy with the cold weather problems to reply so I thought that I?d ask one and all.
  Where I?m up to is that having disconnected the old moshi board, I was left with just two wire bundles, one coming from each of the stepper motors and a simple wiring to the power which I can do easily. It?s the correct wiring from the cnc57 to each of the two stepper motors that I am a little unsure of. Art had previously said in a quote to someone else that there were people here that had done this with these particular boards and could guide me but sadly I have searched and not found any one that fits the bill.
  Anyone that can give this poor old Aussie a hand will be greatly appreciated as this machine could be a great little beastie if I don?t have to run moshidraw and can run Auggie which hopefully will solve all of my laser problems and I can get on with working out my clock designs lol.
Thank you in advance, Phil

Hi Phil,

I am sure you know this already but just in case you don't. The 57CNC cannot drive a stepper motor directly. The Step & Direction signals from the 57CNC motor output connectors are taken to stepper drivers which in turn are connected to the motors. I have no information on your Moshi board but it may be that the existing motor drivers can be used or it may be that new drivers are required.

Tweakie.

not only what tweakie said it would be a good idea to examine the circuitry / voltages around the laser ps modulation input
as you will need create an interface for the pokeys pwm output to provide that signal also

I'm in Australia too  in east Gippsland ,vic  but its a big country.
I have a similar project in mind but would prefer a 50w 500x300 machine , importing a cheap Asian one seems problematical in that
they only want to deliver to capital city ports , too much hassle  think

I would have a close look at this
http://gearotic.com/ESW/FavIcons/index.php?topic=1547.0

tweakie wrote: Hi Phil,

I am sure you know this already but just in case you don't. The 57CNC cannot drive a stepper motor directly. The Step & Direction signals from the 57CNC motor output connectors are taken to stepper drivers which in turn are connected to the motors. I have no information on your Moshi board but it may be that the existing motor drivers can be used or it may be that new drivers are required.

Tweakie.

Thanks Tweakie, no I had no idea that so much was involved but am very grateful for the pointers. Looks like I?ll be dipping into my pocket again for drivers and may as well get new motors as well. At least the people at build your cnc have put some very useful video tutorials out so hopefully that will help too. Thanks for your help mate, we?ll see how the next step goes

Richard Cullin wrote: I would have a close look at this
http://gearotic.com/ESW/FavIcons/index.php?topic=1547.0

Thanks for the helpful tips Richard. This is turning into a much bigger rabbit hole than I had expected but, well, life was meant to be challenging it seems lol. Again, thanks for the help and btw, are you The Richard Cullin of woodworking fame far and wide over here? If so, nice to meet you mate, if not, still nice to meet you lol

Hi Doc:

  As previous letters show, you do need motor drivers to run from auggie.
I know its a bit daunting to get into such rebuilds, good thing is its easier than
youd think looking at all the wires..  

Heres a vexx file showing the general wiring outline of how it all works. There
isnt much to hook up, the diagram shows the main things, laser power, motor hookup..etc. Of course proper ground wires and such are needed, but this is
a general diagram of how to make things work from a cnc57 to Auggie.

(I just recieved 2 new cnc57's as Im about to hook up a new laser with one
over the next couple weeks. Its a good time for you to be hooking up a laser
and asking questions as my multitasking ways have led me back to auggie
and vexx for the next few months work.)

Yell as you have questions,
Art

  Just finally got Auggie driving a galvo cube. Seems to run up to 100K steps per second. Long way to go till Im done but its nice to see jogging on a galvo set, just a
little red dot moving about as you jog. 

  I like the new 57cnc, seems solid, though the pin changes threw me a bit.

Art

are you The Richard Cullin of woodworki ng fame far and wide over here?

no my skill set is in in IT

art love the galvo progress

Just finally got Auggie driving a galvo cube. Seems to run up to 100K steps per second

is that anywhere close to being able to get a POV effect ?
I have been thinking it would be nice to do a POV 300x300 pixel raster display machine .
I have bread boarded a pic based step/dir to dac converter
the step rate is possible into the megabit/sec rate and the 12bit dac is updated every 150uS
I have not gone any further , still pondering the feasibility

the questions I struggle with are
is 12bit dac adequate resolution ?
the cheap ebay galvos have specs that say 20khz pps , what does that even mean ?

is the auggie/pokeys max step rate ever going to be enough ?
just how fast would it need to be to get a POV effect ?

the output of my converter is 0 to 5v  the galvos seem to use -5 to 5v
would that be an issue

Richard:

  Ive been collecting parts for this for a couple years, Im just starting to put it
all together, and Ill probably do a video on it if it all works out, just to save anyone else time that comes behind me, its a lot to figure out as information is hard to come by.

  My galvos, like many you find on ebay from marking heads ( Cambridge scanners )
are pretty quick, I think they were rated at 50K points per second. Im sending more than that , about 100K per second. Mine take +-10volts to work, so Im using a board
called an armfly dac. ( about $35 ) It takes 3.3 volts from my arduino DUE for power, and 40mhz spi to set the dual dac. It puts out dual +- 10 volts, so 1 board will feed 2 galvos. Clever little board even makes the +-10 supplies on its own.

  The CNC57 then, just feeds step/dir signals to the DUE, which then sets the
DAC from interrupts on the step pins. The armfly is 16 bit dac's, so I get 65535 steps
for total field width. That seems too high a res, so Im counting by 2's, making it
really 32767 for width of field. Ive also programmed the arduino to clip at 0 and full count, and put out a home switch signal at any attempt to go below a count of
zero. This makes the CNC57 run fine on its homing routines and the two mirrors
now behave just like any cnc table's axis X/Y drives.

  If your interested in POV, this settup would work for mirror motion, but youd need software to drive them, Auggie couldnt. Auggie relies on the step/dir paradigm, it cant send analogue data values serially, and if it could it would then need a blanking setup as well.

  When done as step/dir, Auggie can use the laser as a normal one, so photo
engraving should be possible with the standard 1ms update rate. The 1ms
laser power loop is important to speed, if you cross the field in .3 seconds
during a photo engraving, thats only 330ms, so 330 power levels from the laser.

  So most of the time one would want to take at least 1 second per raster, for 
1000 power levels of resolution per scan line. I figure most of my time saving
from galvo will be in the acceleration and deceleration removal as the mirrors
dont seem to require any, constant speed is possible on even small curves and corners.

    PPS Speed:  The meaning of PPS is really loose I find. Galvo's it turns out have small angle design or large angle design. If large angle at 30KPS, it means you can virtually send it any ADC count, no matter how different from the previous one and it will move fast enough to do 30K of them per second.

  Mine are very good quality , but I cant do that,  I tried it and the cube got noisy as hell as it pinged around so fast you couldnt see it move. But even if I wanted to use
it that way, it would be a fair amount of work to write software to make it go as youd
have to send an analogue word for each dac for each step. 

  This is why I made the DUE run as a step/dir driver does, simply counting step pulses and updateing the dac when it sees a difference from last dac setting. The DUE
is 84Mhz and seems to be able to do the interrupts at about 100k or so without locking up due to ISR latency.

  So, with 32768 positions from left to right, the pokeys needs to put out
only 32Khz to get a 1 second field sweep, so at 100khz , its about .3 seconds in
theory for the field width and height. If Im lucky with my lens, I may get
300mm width, so res would be 300/32767 so about .009 mm per step. Smaller
lens fields get ridiculous in resolution per step.

  Speed is all about final field size if using it for laser burning. This is probably fast
enough for a sweet engraver, but for POV I  dont think so. The DUE and armfly would work OK I think, but youd have to send it a data frame then tell it to repeat the frame at full speed, then POV wouldnt be an issue.

  Anyway, just a few considerations. Im now waiting for new gold mirrors, my cube was yag and has the wrong mirror type. Then it will be onto the F-theta issue. Theres still a lot of bumps on my road yet I think.

Art