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  1. #1
    Join Date
    Jun 2003
    Posts
    3312

    New board help requested

    I'm working on a new driver board based on a Atmel's AVR's (single chip micro) for the open source forum here. Long term intent is to have a low cost DIY three axis board, that will also have the pport connection and interface for limit switch and spindle. Attached is a grapic of a one axis board layout and schematic for software development. I doubt if I can get to doing an this actual board for several month's. If somebody would be willing to etch or mill one for a minimal fee, I could get to work on firmware.
    Or if somebody want to do some code, or.........

    The Attiny2313 is fast enough to handle a simple edge filter to make the input filter circuit on my other boards unnecessary. It is also inexpensive. It should be able to handle half step as well as full steps simply. The 3 axis board would have three of them.

    Cost wise the 2313 is about $2.25 and the fets show are about $1.50 each. That adds up to a 3 axis board that could probably be built for under $45 worth of parts.

    Phil
    Attached Thumbnails Attached Thumbnails avrschematic.png   avrboard.png  

  2. #2
    Join Date
    Feb 2004
    Posts
    361
    If all you want a couple to evaluate the design with, I can pop off some quick TT style boards..
    just give me a mailing address..

    got some going in the etch tank tomorrow am.. can do easily,,all I need is Gerber, or Eagle / Pulsonix..

  3. #3
    Join Date
    Jun 2003
    Posts
    3312
    Vladdy,
    Look at your email. Thanks,
    Phil

  4. #4
    Join Date
    May 2004
    Posts
    200
    cound you tell me what the fed numbers are.

  5. #5
    Join Date
    Jun 2003
    Posts
    3312
    Irlz44

  6. #6
    Join Date
    Jan 2005
    Posts
    1695
    I'm playing with a similar designed based on a at90s2313 and a irl530. The result was very unsatisfactory. To get speed, it is necessary to use a high (35-45v) power supply and a chopper to control the current. A chopper can be implemented by adding a lm324 op amp to use as a pair of comparators to detect the coil current. With the o/p going to interrupts, the mcu can turn off the drive for a fixed time whenver the setpoint is exceeded.

    I will try it this week as soon as I have time to write the program.

  7. #7
    Join Date
    Jul 2003
    Posts
    6
    One of the issues here may be the drive capability of the micros. The irlz44 etc
    have fairly large gate charge requirements (66nC). You may need to use some sort
    of buffer circuit to drive the fet gates to get them to switch fast.

    jazz

  8. #8
    Join Date
    Aug 2004
    Posts
    2849
    Quote Originally Posted by pminmo
    Irlz44
    If the FETs aren't the logic gate types...then that processor most likely won't be able to turn on the FET. Also I didn't check if you could do bit operations on the Micro's ports.

  9. #9
    Join Date
    Jun 2003
    Posts
    3312
    H500,
    To get the best speed out of a stepper, you have to run a higher PS voltage and current limit.
    Jazz,
    That is a concern, one of the reasons I wanted to protype.
    Viper,
    The AVR is bit programmable, and yes the FET is logic compatable.

    Phil

  10. #10
    Join Date
    Feb 2004
    Posts
    361
    Got the PCB's out by snail the other day, bit of a delay, toner cart ran low in the HP, and topped up with generic toner, not as clean as before, so photo etched...
    last photo is TT, piss poor..but good enough for a 'trial' anyways

    you should have them in a few days..

    enjoy..
    Attached Thumbnails Attached Thumbnails IM000194.JPG   IM000195.JPG   IM000196.JPG  

  11. #11
    Join Date
    May 2004
    Posts
    200
    Quote Originally Posted by vladdy
    Got the PCB's out by snail the other day, bit of a delay, toner cart ran low in the HP, and topped up with generic toner, not as clean as before, so photo etched...
    last photo is TT, piss poor..but good enough for a 'trial' anyways

    you should have them in a few days..

    enjoy..
    did you etch you boards or have them done?

  12. #12
    Join Date
    Jun 2003
    Posts
    3312
    vladdy,
    Thanks.

    Phil

  13. #13
    Join Date
    Feb 2004
    Posts
    361
    Quote Originally Posted by tekno
    did you etch you boards or have them done?
    etched in the basement.. the copper appearance single PCB was done with Toner Transfer, but my toner on the old HP was getting poor, and the 'generic' toner I used to top up wasn't quite fully compatible..pretty messy..
    factory toner in that HP [300dpi] gives half decent transfers at 16mi, maybe 95% acceptable at 12mi, to get consistent 12mi I should actually have a 600 dpi laser.. For most of my hobby stuff I run 20mi signal and 24mi supply widths..no screwups, quick results..
    The bluish set of three PCB's was photo etched, a little faster, cleaner, better quality, but more expensive.. probably $4 CDn for actual photo sensitized board cost for that size..
    Silkscreen is better for [me anyways] for quantities of 5 plus.. a little slower because of drying time, and probably the cheapest of all for larger quantities.
    The top placement overlay on the bluish ones was Toner Transfer again, useable but not 'professional' quality..
    I did a quick silkscreen with 160 on these, but 12mi isn't very 'neat', useable, but not really nice looking, need 255 or better for 12mi, I use 160 for 20/24mi and the quality is reasonably good..
    After all, this is just a hobby??

    enjoy..
    Attached Thumbnails Attached Thumbnails IM000198.JPG  

  14. #14
    Join Date
    May 2004
    Posts
    200
    hows this going?

  15. #15
    Join Date
    Jun 2003
    Posts
    3312
    Vladdy's board hasn't arrived yet. WIll update when it does.

    Phil

  16. #16
    Join Date
    Feb 2004
    Posts
    361
    and you still have some work to do before that..
    code to check..
    board to populate...
    oh yeah, and you said you would drill the board ...

    that's the part I'm not too fond of..

    Just might have to make a drilling table.. just a hand one, probably faster than doing a cnc setup and registering, especially for small [read 4 or less] quantities..

    should still have some small linear slides around here someplace..probably drill from bottom up, need some kind of alignment pin..dremel mount, another dremel [again], maybe a small magnifying glass, just in case...
    maybe not, that way there will be a built in excuse if they are 'just a tad' off center..

    great, another project...

  17. #17
    Join Date
    Jun 2003
    Posts
    3312
    vladdy,
    Very true, I thought I was the only one out there that juggled a dozen projects. :-) Have to say a pcb router is dancing in my head...............

    Thanks for your help,
    Phil

  18. #18
    Join Date
    May 2004
    Posts
    200
    Quote Originally Posted by pminmo
    vladdy,
    Very true, I thought I was the only one out there that juggled a dozen projects. :-) Have to say a pcb router is dancing in my head...............

    Thanks for your help,
    Phil

    Ya... I think my mill will be the second thing I finish.. pcb router has been moved to first.

    Tek

  19. #19
    Join Date
    Feb 2004
    Posts
    361
    The coating on the set of three is the photo resist, I didn't bother removing it after etching, makes a good protective layer to help against corrosion, especially if it's going to sit for a while..It's not too bad to solder on top of, I use a Haako set around 550 degrees, gives a bit of a poor mans solder resist otherwise..can be scrubbed off with acetone, or polished off with a scotchbrite pad, tin if you want.. their your's now..

    The single one was Toner Transfer.. not very good..traces should be widened up a bit, and a little more isolation, especially on the one end with three small traces to make it a little more 'idiot proof'..
    I did a quick silk screen for these, but all I had was 160 line silk, results on a few trials came out 'fair'.. either a wider [024, 020 ??] trace would work better, or 255 line silk to get proper definition.

    You should have mentioned you needed some 2313's.. I've got a few dozen left over from a old satellite project...let me know if your's are going to take a while to come in..mail got there faster than I expected it would..

    how's the code coming??

    enjoy.

  20. #20
    Quote Originally Posted by vladdy
    You should have mentioned you needed some 2313's.. I've got a few dozen left over from a old satellite project...
    An old satellite project ehh? Sounds pretty cool. :cheers:

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