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  1. #1
    I'm running 3 Leadshine AM822 drivers with 2 at more or less their maximum current (5.86A RMS) and my 36v switch-mode power supply just isn't up to it.

    I've been recommended to buy an unregulated supply of around 60-70v. I'm guessing that a 10A supply will be enough to drive all three motors (the Z axis requires very little power). Can anyone recommend a supplier or a method of construction.

    While I currently have just 3 axes but might want to increase to 5 although the 4th and 5th will need lower power motors.

  2. #2
    Quote Originally Posted by Agathon View Post
    I'm running 3 Leadshine AM822 drivers with 2 at more or less their maximum current (5.86A RMS) and my 36v switch-mode power supply just isn't up to it.

    I've been recommended to buy an unregulated supply of around 60-70v. I'm guessing that a 10A supply will be enough to drive all three motors (the Z axis requires very little power). Can anyone recommend a supplier or a method of construction.

    While I currently have just 3 axes but might want to increase to 5 although the 4th and 5th will need lower power motors.
    Ok I am in Spain after a bit of vino But here is a link http://www.zappautomation.co.uk/ps80...er-supply.html but you could build your own for nearly half the price with bits from Rapid on line. https://www.rapidonline.com/electronic-components
    ..Clive
    The more you know, The better you know, How little you know

  3. #3
    Thanks Clive - I bet it's hot there!

    I've seen those rectifier/smoothing capacitor boards on most home-built PSUs are they available from eBay and Aliexpress? Not quite sure what to search for.

    Enjoy you holiday!

    David

  4. #4
    Having thought about it, I only need to run 2 of the AM822s from a 60-72v PSU. If they are set at their maximum current what sort of VA do I need from the transformer? I'm guessing this will partly depend on the specification of the smoothing capacitors.

  5. #5
    Quote Originally Posted by Agathon View Post
    Thanks Clive - I bet it's hot there!

    I've seen those rectifier/smoothing capacitor boards on most home-built PSUs are they available from eBay and Aliexpress? Not quite sure what to search for.

    Enjoy you holiday!

    David
    The boards I think you are referring to are not suitable as they have very small caps on them.
    ..Clive
    The more you know, The better you know, How little you know

  6. #6
    Have a look at Joe's recent build:
    http://www.mycncuk.com/threads/4513-...-router/page19
    post #373 onwards

    And mine from a while ago:
    http://www.mycncuk.com/threads/6988-routercnc_MK3/page3
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  7. #7
    Quote Originally Posted by Agathon View Post
    Having thought about it, I only need to run 2 of the AM822s from a 60-72v PSU. If they are set at their maximum current what sort of VA do I need from the transformer? I'm guessing this will partly depend on the specification of the smoothing capacitors.
    Some links here.
    https://www.rapidonline.com/50a-brid...al-case-519318

    https://www.rapidonline.com/samwha-h...acitor-11-3121

    https://www.rapidonline.com/lcr-ep08...-clamp-11-3004

    This has secondary of 25-25v some people like 24 - 24V
    https://www.rapidonline.com/vigortro...-x-25v-88-0005

    And a vid by Joe. He used 4 caps but three is fine.
    https://www.youtube.com/watch?v=4OoQQg76ar4
    https://www.youtube.com/watch?v=WISDqx-e23M
    ..Clive
    The more you know, The better you know, How little you know

  8. #8
    Many thanks.

    What do you think about power output. I'm running the 2 AM822s at 5.8A RMS (actually, I think that once I have the interface cable I'll programme the drives to 5.5A RMS (2.8 x 1.96) - but that's splitting hairs) so that's total RMS current of 11.6A. The AM822 manual says that 50-70% of the motor current will be sufficient.

    So 2 x 5.5A = 11.0A. 50-70% = 5.5-7.7A x 70v = 385-539VA. So a 500VA transformer should be OK?

    Does that sound right or should I be working with the AC output voltage of 50v?

    I see that Joe used a massive 750VA transformer.

  9. #9
    Is there a reason you are using just two motors like it is a lathe?

    I run 4 nema 23 on my router without problems and 3 on the mill both with 500va transformers the next one up is 625va.

    Remember that the motors rarely all run at peak current together.
    ..Clive
    The more you know, The better you know, How little you know

  10. #10
    GND's Avatar
    Lives in Cambridge, United Kingdom. Last Activity: 05-08-2018 Has been a member for 3-4 years. Has a total post count of 61. Received thanks 2 times, giving thanks to others 11 times.
    And your calculations should use the AC rather than the DC voltage as the factor into the VA rating - so your figures immediately fall by a factor of 1.4! The DC output is essentially the peak value of the AC voltage, having been rectified and filtered, whereas the VA rating is RMS.

    Hope that helps!
    Graeme

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