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  1. #1
    Hi,

    I am building a steel CNC, working area 2m x 1.3m x 0.3m.

    I have:
    X (2m): TWO nema 23 425oz coupled with TWO SFU2010 ballscrews
    Y (1.3m): nema 23 450oz coupled with SFU1610
    Z (0.3m) nema 23 425oz coupled with SFU1605
    Gantry weight will approximately be 60-80kg.
    All axis roll on SBR20UU blocks/rails.

    Very standard setup for a large steel gantry type machine. All axis

    After using the "required driver voltage" calculator provided on this forum, I figured I would need 60-80VDC drivers. After reading this forum for a while, I think I'll buy Leadshine AM882 drivers (http://www.aliexpress.com/item/inSto...258905084.html).

    I have the following questions:
    1. What do you think about this driver choice ?
    2. Can you recommend to me a PSU to buy ?
    3. I already have 24V-36V drivers and a 24-48V PSU, what can I do with those ? Can I may be use the PSU to power my controller ?

    Thanks a lot for your help.

    PS: I'm experimenting a proof of concept of no welding steel structure, only nut and bolted. Will tell more in a few days / weeks when design is ready :) All parts will be plasma cut. But that's another discussion.

  2. #2
    Ringkerntrafo (Diverse Ausgangsspannungen und Leistungen)( 171780992858 )

    2x50VAC 500W , that rectified will give you 2x70VDC, combined with the AM822 drives
    project 1 , 2, Dust Shoe ...

  3. #3
    Hi ! Thanks for you reply ! I have been reading your build logs, amazing work !

    I don't quite understand what you are explaining though.. with the very little electrical knowledge I got, I understand so far that I need a PSU that can deliver at least 80VDC and 8A (based on 4 * 2.8 * .7 amps, calculated from CNC 4 Everyone basic knowledge page).

    I am right so far ?

    Do I need a regulated or unregulated PSU ?
    Last edited by eurikain; 17-08-2015 at 03:46 PM.

  4. #4
    what i learned here on the forum here from Dean

    -to get the needed transformer necessary secondary winding voltage we divide the 70DC/1.4= 50 Vac
    -due to the fact that the drive uses PWM - On and Off cycle, the actual current use will be 60-70% at most , so say using 4 x 4.1A motors =16.4A so 65% = ~ 10.6A
    so at 50VAC and ~10A, we are looking at 500W toroid transformer
    -the secondary 2x50VAC must be wired in parallel !
    -capacitor has to be around 10 000
    mf for that setup , at least x1, more will not hurt, it must be >100VDC rating
    - >35A 100Vdc Bridge rectifier, the bigger the better, heatsink

    That will give you on output 50VACx1.4=70VDC when rectified


    project 1 , 2, Dust Shoe ...

  5. #5
    Alright, I guess my case is worse than I thought. I appreciate the effort you put into explaining this to me, but am unfortunately not smart/good enough with electronics to understand what you are explaining...

    Let me explain what I understand:
    - You're explaining a way to build my own power supply. I don't really feel comfortable building it myself. I'd rather have an already built power supply..
    - I am using 3 x 2.8A motors (here is their spec sheet) plus 1 x 3.2A motor (here is its spec sheet). I connect to each of these motors an AM882 driver. I calculated 80VDC required, and 3*2.8+3.2 = 11.6A required. However, I understand that because of the PWM On/Off cycle mode of the AM882 (as you explained, but as I also read in AM882 manual), only 60-70% of the theoretical voltage is needed. That leaves us with the following requirements: 56VDC (70% of 80VDC), 8.12A (70% of 11.6A).

    That's where I loose you... I don't know what transformers or primary/secondary capacitors are, what they're used for, why I need them, and where I wire them... I most likely have missed some thread on the forum explaining the basics of building your own power supply :/

    The only thing I understand clearly is that I need a power supply that can provide 56VDC and 8.12A and that anything above is of no hurt but to my savings.

    Or am I just completely off the line and you are giving me a list of criteria to select the right power supply ?
    Last edited by eurikain; 17-08-2015 at 08:35 PM.

  6. #6
    Seems you are over complicating stuff. Its very simple to make and connect, see picture.

    You need 2x50VAC 500W transformer, 10000f 100VDC CAPACITOR and 100V 15A or more bridge rectifier



    Buy the stuff and people here on the forum will help you make it. Obviously the schematic is super simple.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    project 1 , 2, Dust Shoe ...

  7. #7
    Quote Originally Posted by eurikain View Post
    Alright, I guess my case is worse than I thought. I appreciate the effort you put into explaining this to me, but am unfortunately not smart/good enough with electronics to understand what you are explaining...

    Let me explain what I understand:
    - You're explaining a way to build my own power supply. I don't really feel comfortable building it myself. I'd rather have an already built power supply..
    - I am using 3 x 2.8A motors (here is their spec sheet) plus 1 x 3.2A motor (here is its spec sheet). I connect to each of these motors an AM882 driver. I calculated 80VDC required, and 3*2.8+3.2 = 11.6A required. However, I understand that because of the PWM On/Off cycle mode of the AM882 (as you explained, but as I also read in AM882 manual), only 60-70% of the theoretical voltage is needed. That leaves us with the following requirements: 56VDC (70% of 80VDC), 8.12A (70% of 11.6A).

    That's where I loose you... I don't know what transformers or primary/secondary capacitors are, what they're used for, why I need them, and where I wire them... I most likely have missed some thread on the forum explaining the basics of building your own power supply :/

    The only thing I understand clearly is that I need a power supply that can provide 56VDC and 8.12A and that anything above is of no hurt but to my savings.

    Or am I just completely off the line and you are giving me a list of criteria to select the right power supply ?
    What Boyan is telling you is basically correct but if you want to purchase one off the shelf see here. http://www.zappautomation.co.uk/elec...er-supply.html to get the best results from your drive and motors you will need about 60 - 70V .. Clive
    ..Clive
    The more you know, The better you know, How little you know

  8. #8
    Quote Originally Posted by Clive S View Post
    What Boyan is telling you is basically correct but if you want to purchase one off the shelf see here. http://www.zappautomation.co.uk/elec...er-supply.html to get the best results from your drive and motors you will need about 60 - 70V .. Clive
    Great, i was wondering where i saw them assembled but couldn't remember
    project 1 , 2, Dust Shoe ...

  9. #9
    Quote Originally Posted by Boyan Silyavski View Post
    Seems you are over complicating stuff. Its very simple to make and connect, see picture.

    You need 2x50VAC 500W transformer, 10000f 100VDC CAPACITOR and 100V 15A or more bridge rectifier

    Buy the stuff and people here on the forum will help you make it. Obviously the schematic is super simple.
    Hallelujia, I now understand ! I am quite amazed by the fact that it's so simple ^^.... Thanks also to Clive for providing the links :) Now that I understand how easy it is, I feel much more comfortable making it myself !

    While I am writing this I am looking for the parts you provided on AliExpress instead of Ebay (don't have an ebay account, neither a paypal account, and I don't plan on making one :p.. I have taken a great pleasure at buying stuff on AliExpress :D Those chinese guys can be amazing :D ! Got 2x2m SFU2010 + 1x1.3m SFU1610 + 1x0.5m SFU1605 + end supports + couplers + free shipping for 340 Euros !

    I still have unknown areas:
    1. How am I going to connect this to the wall, taking into consideration that I am using 220VAC (does that even matter ?)
    2. How am I going to connect all my AM882 to the board ? All in parallel ?
    Last edited by eurikain; 17-08-2015 at 11:46 PM.

  10. #10
    Ok see this:- http://www.rapidonline.com/
    I think you need to read up here and do a search on the forum as there are many posts on building control panels so that you will understand the basics.
    .
    Things like earthing, grounding with star ppoints etc. be aware that with the transformer that the mounting bolt must ONLY be earthed at one end ie do not connenct any earth to the top end of the bolt (this would create a shorted turn on the transformer).
    .
    You will need cy 4 core 1mm or 1.5 mm cable for the motors and spindle. (earth the braids at the control box only to a star point).
    .
    If you put up a circuit diagram people on here will take a look and check it out.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Rapid_on_line.JPG 
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    Last edited by Clive S; 18-08-2015 at 07:50 AM.
    ..Clive
    The more you know, The better you know, How little you know

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