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  1. #1

    Join Date
    Dec 2018
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    Reducing voltage from power supply

    My Gecko 201x drives max out at 80v. The guy at Antek advised me to go with a 77v power supply to be safe, but I tested it today and its output measures 82v. What's the best way to limit that to 80v?

    This is what I have: https://www.antekinc.com/ps-10n77-10...-power-supply/

    The 24v output measures 25.2, so I'll need to reduce that to 24v for my BoB.

    The 12v and 5v outputs are fine.

  2. #2

    Re: Reducing voltage from power supply

    I don’t think I’d worry about it.

  3. #3
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    Re: Reducing voltage from power supply

    Quote Originally Posted by Sam_Beckham View Post
    I don’t think I’d worry about it.
    Nor do I....The PS is rated at 77V so it will probably will drop down close to that under load. All good.

  4. #4

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    Re: Reducing voltage from power supply

    That's fantastic news. Thank you both. I've spent the last six hours in various rabbit holes looking for a way to remedy this.

    I had just begun reading about how to wind my own resistor when I refreshed this page.

    Thanks again.

  5. #5
    Community Moderator Al_The_Man's Avatar
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    Re: Reducing voltage from power supply

    If you did have to do it, just take a few turns off the secondary, usually around 2 turns/volt.
    Very easy on a toroidal transformer
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #6

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    Re: Reducing voltage from power supply

    Quote Originally Posted by Al_The_Man View Post
    If you did have to do it, just take a few turns off the secondary, usually around 2 turns/volt.
    Very easy on a toroidal transformer
    Al.
    I've watched a few videos on diy toroid winding (just out of curiosity) so I wondered if unwinding a few turns was an option. The toroid is wrapped so neatly, though...

    I was also wondering how 'load' is defined exactly. While the machine is running? Sure, but what about powering up or on standby? Is it possible that the PS will throw too much voltage to the drives and BoB for a period of time, albeit brief? Or just having everything powered up at once (sensors, led gantry downlighting, BoB, expansion boards, drives, etc) be enough? The 240v supply going into the control box will also power the vfd which will be mounted on the outside. Maybe that will pull enough ac voltage to help mitigate.

    Further, and don't ask me why this is the case, but one leg of the AC measures ~120v and the other is ~125v. Maybe that's the problem? Maybe that's a bigger problem that I need to deal with first?

  7. #7
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    May 2004
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    Re: Reducing voltage from power supply

    You are probably measuring it completely unloaded. I you are concerned, measure it under a load. Best load is the intended equipment but you can also test it with a power resistor for the load. 200 ohm, 50 Watt would be good. You can get one from amazon for $8ish.

    I doubt that 6.5% over-voltage will damage anything. However watch your electronics temperature. A contactless thermometer is a useful thing to have in general.

  8. #8
    Community Moderator Al_The_Man's Avatar
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    Re: Reducing voltage from power supply

    Quote Originally Posted by gr-cnc View Post
    I've watched a few videos on diy toroid winding (just out of curiosity) so I wondered if unwinding a few turns was an option. The toroid is wrapped so neatly, though...
    I have modified a few toroidals over time, also added a few with overwinds to produce a small aux supply etc.
    The transformer is rated in Va, so as long as the value is kept in mind, it is fairly flexible, lower the turns and you can increase the current rating of the winding proportionately, providing that the wire gauge is sufficient.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9

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    Dec 2018
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    Re: Reducing voltage from power supply

    Good point. A shelf bracket, for example, will be rated for xlbs, but in reality it will hold twice that. There's hopefully some wiggle room.

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