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  1. #1

    Cheap drives?

    Hi,

    I'm interested to know what your thoughts are if Geckodrive should
    produce an inexpensive, board-level drive. Target specs are:

    1) 3A per phase, 50VDC max. Discrete all n-channel MOSFETs.
    2) 10 microsteps per step, CPLD design.
    3) No midband resonance compensation, no morphing.
    4) No trimpot crossover adjust.
    5) Audibly silent design (not a chopper, same PWM as a G203V).
    6) No plate, no can, no nice connectors. Just a board and header.
    7) No opto-isolator.
    8) No heatsinking needed. Everything is surface-mount.
    9) No protection circuitry.
    10) Target price: $29 single quantity.

    This proposed drive would be a derivative of the G203V stripped of all expensive items and many features in order to fit it into a $0.99 CPLD. It would still be a dual all n-channel full-bridge design using 20A rated discrete MOSFETs. Not a fragile monolithic IC design.

    The idea is to make a bottom-price yet quality and rugged step motor drive. The "bang for the buck" equation works out to:

    3A times 50VDC divided by $29 equals 5.17 as the value number. Try this equation on other drives. The bigger the number, the better the value.

    Mariss

  2. #2
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    For me the question isn't whether or not you should make them, the question is "Are they ready yet ?"

    Russell.

  3. #3
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    Are they shipping yet?

  4. #4
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    Yeah I'll have three thanks.

    How do these four specs compare to say the Xylotex?

    3) No midband resonance compensation, no morphing.
    4) No trimpot crossover adjust.
    5) Audibly silent design (not a chopper, same PWM as a G203V).
    7) No opto-isolator.


    I guess this is a considerable difference
    "It would still be a dual all n-channel full-bridge design using 20A rated discrete MOSFETs. Not a fragile monolithic IC design."


    Greg

  5. #5
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    Hi,

    I think they are going to be welcomed. Go ahead!!

    Kreutz.

  6. #6
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    I think they will be a great success!

    Just out of curiosity, which CPLD do you intend to use?

  7. #7
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    I think you would sell a boatload..........
    Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
    Vist my websites - http://pminmo.com & http://millpcbs.com

  8. #8
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    Sorry to get a bit off the subject… but still within the new product arena….

    I would love to see gecko come out with a “dumb” IO product to bridge the gap between your drive’s and the PC. I own a GREX and have been very happy with it even though it was probably overkill for my application. I was mostly looking for the extra IO and external pulse generation then its ability to control motion by itself. I would think there would be a decent market for a product like this.

    Maybe something with:
    - Let’s the PC do all the thinking like other BOB’s
    - Ethernet (I love this about the grex) or USB connectivity
    - Pulse generation?? (I think this might make interfacing software much more complex.)
    - Opt isolated
    - Lots of IO
    - More easily integrated with mach3 / emc / etc.
    - Charge pump
    - Drives can plug directly onto the board to reduce wiring.
    - Foolproof like the G203V

    I guess the question would be if you all just want to keep manufacturing mainly drives and if there would be a way to reduce the amount of support a device like this might consume for Gecko.

    On a side note I think there might be a market for a new low cost drive but I’ve been very happy with your current product offerings and think they are priced well.

  9. #9
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    It is better to have protection circuitry
    www.kelinginc.net

  10. #10
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    Xitian, I understand where you are going, but we are drive manufacturers. We try to avoid producing anything but what we can do well, and that is motor controls. When we bring out a new product, the first thing we think about after designing is the support for the product. If we were to have a wide range of products, then we would have to also be proficient in our support of a wide range of products. This is something we may reconsider further down the road, but for right now we are going to just stick to motor controls.

    CountZero: We intend to use the Xilinx CoolRunner II XC2C32A QFG32 CPLD. This will be small enough and cheap enough for us to mass produce the drives with. I am actually typing this while taking a break from programming the first revision of the drive, just to see how feasible it is to do. I feel fairly confident about this being doable, but I think slightly less so than my dad ;-).

    -Marcus Freimanis

  11. #11
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    This is a good Idea, any target price you have in mind.

    I would think that you will want to be slightly higher than the 50v mark, because allot of people can have 48vdc easily.

    You can call it the BG203 (Baby Gecko)
    Attached Thumbnails Attached Thumbnails BG203.jpg  

  12. #12
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    I think a reduced cost/functionality servo/stepper drive would be good. In my personal affairs, I run the G210 and G340 at 24VDC, at around 3 Amperes. This proposal fits within my requirements quite well. The price is also less demanding on the budget. I have a MAX-NC mill that I want to set up like my Sherline, running Mach3.

    I currently don't use any of the features of the G210. I simply connect a break-out board to the PC and rely on the G210 optocouples for isolation. I could move the isolation to the break-out board.

    Great idea! I'll take at least 3...

  13. #13
    Community Moderator ger21's Avatar
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    If you could do 5 amps for even $20 more people would still be knocking down your door I think.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  14. #14
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    I definitely would. I looking for a simple/cheap-ish stepper driver/controller for a desktop sized cnc setup like the thing on instructable.com a light moving table for me so i don't need drivers made to power nema 23's to move a big honkin mdf gantry. Something like that would be overkill for what i need.Besides they would be a good entry level option for beginners to dip their toe in and get some play time with without having to spend ungodly amounts of money before they even know what they're doing.

  15. #15
    It's been a good day. The Cheap Drive now has mid-band compensation and morphing added.

    We just compiled the design and it fits into the 32 macrocell Xilinx XC2C32A-6-QFG32 CPLD; just barely:

    Macrocells used = 32 of 32. 100% of available.
    Pterms used = 79 of 112. 71% of available.
    Registers used = 31 of 32. 97% of available.
    Pins used = 17 of 21. 81% of available.
    Function Block inputs used = 42 of 80. 53% of available.

    The CPLD design has passed all simulation tests which proves the logic design is sound. Someone here suggested calling it a Ghettodrive.:-)

    Mariss

  16. #16
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    Type of Drive

    Mariss

    Is the new GhettoDrive going to be Unipolar or Bipolar?

  17. #17
    Bipolar all the way. 20A at 60V rated all n-channel MOSFET dual bridge and a synchronous 20kHz PWM circuit (not a chopper, completely silent). Anti-resonance, morphs from microstepping to full-step at high speeds.

    Mariss

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    Why would you want to lower the price of cnc that low? There would be no margin for your resellers. Whats the point.
    Do you want to be the WalMart of stepper drives ?

  19. #19
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    This was the start up:
    3A times 50VDC divided by $29 equals 5.17 as the value number. Try this equation on other drives. The bigger the number, the better the value.
    SO now at
    20A at 60V rated
    If you keep the value 5.17 its gonna cost me over 200 BUCKS! Bugger! -- Or can it still be under $50 per axis? Then, thats a value of 24! AWESOME!
    :cheers: Jim
    Experience is the BEST Teacher. Is that why it usually arrives in a shower of sparks, flash of light, loud bang, a cloud of smoke, AND -- a BILL to pay? You usually get it -- just after you need it.

  20. #20
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    Whats wrong with shopping at Walmart

    I applaud Gecko for offering the GhettoDrive, isnt there a lid for every garbage can?

    Resellers should provide value added to the products they sell, otherwise why would anyone purchase from them?

    You know Ace Hardware stood still while Home Depot almost kicked them completely out of buisness!

    I look forward to seeing the outcome of this race!

    Jeff Alessi
    jalessi@aol.com

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