Converting AC voltage to DC voltage?
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  1. #1
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    Default Converting AC voltage to DC voltage?

    I have a little project for the shop at home. Trying to build a belt sander. I have a 115 V DC treadmill motor that I would like to use. This would facilitate varying the speed , making it much easier. The motor is 2.0 HP Continuous [email protected] 115 VDC/1492 watts. I need to figure out how to convert straight 110 Volt AC current to something this motor can use. What are the groups suggestions?

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    You need to match that with a suitable dc speed controller. Simply rectifying ac would result in too high a voltage because 115-120v ac is the RMS value rather than the peak, which is nearly 50% higher.

    EDIT: If you have the rest of the treadmill a fairly simple pulse generator circuit can be made to provide input, since all modern treadmill controllers are AFAIK designed for pulse controlled input rather than using a potentiometer like the older ones.

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    What happened to the rectifier in the treadmill?

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    You want to convert AC current to DC current.
    Voltage is a verb, not a noun.

    -Doozer

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    First this is stupid simple and very complicated as well.

    Simple diodes will convert but you need a motor controller.

    Look at the motor and determine just 2 things.

    Operating voltage and maximum current.

    Now search for a pre made motor controller rated for same voltage and slightly higher current and call it a day.

    The assumption is since you are asking you may not have the skill set to make one and buying ready made is fast and easy and not that expensive.

    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    Maybe replace treadmill tread with sandpaper, and call it a day?
    Many home shop references abound covering use of these motors with aftermarket/surplus controllers.
    Just not many here on PM.

    But then, I'm still trying to figure out how 'voltage' is a verb.
    Yeah, I get that it's pressure, and an 'active' thing, but...

    Chip

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    I thought those treadmill motors were way too slow for something like a sander. Maybe they have a gear reduction that can be removed?

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    There are treadmill motor contollers on eBay. We are building a sander for grinding knife blades. We used the one on the second link. It works nicely. The motor we have is a 2hp and has lots of speed and torque.

    controller for DC treadmill motor | eBay

    Icon MC21LTS-3 DC Motor Variable Speed Replacement Controller For Treadmills | eBay

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    easy. go to a thrift store and buy another treadmill . goodwill and habitat stores sell them for $25-$30 all day long.

    if you make the thing belt driven, then you can get the speed where you want it with pulleys.

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    Default DC controller

    I found a great company, Dart Electronics. Many sizes f AC to DC power supply, and speed controller.

    A 2HP is around $200 on ebay $75+. I have several units and am very pleased with the units. Then even repair units, after you fry the thing. But thats a different story.

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    Quote Originally Posted by Doozer View Post
    You want to convert AC current to DC current.
    Voltage is a verb, not a noun.

    -Doozer
    Currently, I volt people that come to my house. That way they go ohm.

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    Watts up with that?

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    Most of the older controllers had a full wave bridge rectifier for the motor, and a triac based control on the AC side of the rectifier for speed adjustment (basically a more sophisticated version of a light dimmer). Some had speed feedback, some did not.

    The stupid simplest "speed control" is a full wave rectifier setup, with a variac for AC amplitude control. You can get as complicated as you want after that.

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    Quote Originally Posted by Rich L View Post
    Currently, I volt people that come to my house. That way they go ohm.
    This thread has jumped the shark...

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    Quote Originally Posted by Toms Wheels View Post
    I found a great company, Dart Electronics. Many sizes f AC to DC power supply, and speed controller.

    A 2HP is around $200 on ebay $75+. I have several units and am very pleased with the units. Then even repair units, after you fry the thing. But thats a different story.
    I had a Dart on a DC motored machine, it was surprisingly cheap and surprisingly high performance. Eventually went 3phase on that one and don't look back but if I had a high quality DC motor in hand and a machine that needed it would likely go Dart again.

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    Actually that is not true. There is a reason why 115V DC motors are somewhat common. That reason is that you can JUST rectify the 115 VAC power directly from a wall socket to a pulsating DC and it should work. It is the RMS value of the Voltage that counts and if there are no filtering capacitors, then, even though the peak value of the rectified 115 VAC will be around 160 Volts, the RMS value will still be 115 V (DC).

    If you add filtering capacitors, then they will try to charge up to that 160 Volt value and that will be too high for a 115 VDC motor. So, LEAVE THE FILTERING CAPACITORS OUT.

    It is also easy to add a speed control to that pulsating DC in much the same manner that AC speed controls are made by switching the waveform on and off at various phase angles.



    Quote Originally Posted by Scottl View Post
    You need to match that with a suitable dc speed controller. Simply rectifying ac would result in too high a voltage because 115-120v ac is the RMS value rather than the peak, which is nearly 50% higher.

    EDIT: If you have the rest of the treadmill a fairly simple pulse generator circuit can be made to provide input, since all modern treadmill controllers are AFAIK designed for pulse controlled input rather than using a potentiometer like the older ones.

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  21. #17
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    I watt UL to NO watt I volt last Tuesday, OHM the DC was Electriced.


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