Why a 24Volt Power Supply?

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Ts127
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Why a 24Volt Power Supply?

Post by Ts127 » Sun Aug 12, 2012 3:21 am

Hi all! I'm new to this forum and the cnc scene so forgive me if I make a complete fool of myself :) . I have ordered a shapeoko mechanical kit and i'm looking into purchasing the electronics, But the 24v power supply confuses me. Why do I need 24volts when the recommended nema 17 steppers are rated for only 3v? I have looked into it and haven't found any answer that constitutes the use of this robust of a power system. Any explanation or suggestion of places to look of answers is greatly appreciated.

Thanks,

Tyler

Colecago
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Re: Why a 24Volt Power Supply?

Post by Colecago » Sun Aug 12, 2012 3:43 am

Someone else can probably explain this better who is more familiar with stepper motors, but I believe the higher voltage makes them step faster and thus they see pulsed voltage for a shorter period of time. This also results in cooler operation as well.

potatotron
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Re: Why a 24Volt Power Supply?

Post by potatotron » Sun Aug 12, 2012 4:35 am

The stepper drivers are sometimes called choppers, because they chop up the power into bites, basically switching on and off rapidly. So no matter what source voltage you use (up to the limits of the chips, usually around 30 volts) they'll only give the motors what they need.

To use the oft-quoted water analogy, more voltage is like higher water pressure. Think of the choppers filling up power buckets for the motors; more water pressure means these buckets can get filled faster.

So the higher the voltage, the faster the choppers can fill up the motors; the end result is more torque.

baz
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Re: Why a 24Volt Power Supply?

Post by baz » Sun Aug 12, 2012 10:49 am

potatotron wrote:The stepper drivers are sometimes called choppers, because they chop up the power into bites, basically switching on and off rapidly. So no matter what source voltage you use (up to the limits of the chips, usually around 30 volts) they'll only give the motors what they need.

To use the oft-quoted water analogy, more voltage is like higher water pressure. Think of the choppers filling up power buckets for the motors; more water pressure means these buckets can get filled faster.

So the higher the voltage, the faster the choppers can fill up the motors; the end result is more torque.
Great explanation :D I have being a bit unsure about this myself, thanks
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Digitalmagic
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Re: Why a 24Volt Power Supply?

Post by Digitalmagic » Fri Aug 24, 2012 9:27 am

The stepper motor specification indicates, among other, coil voltage and max amperage.
The stepper driver usually feature a current limiter (adjustable pot).

A stepper driver can be supplied with a voltage range, according to its specs.
With a higher voltage, the driver deliver a faster power ramp, up to the current limit, set by the pot.
The back-EMF produced by the coil is like a voltage to be subtracted from supplied voltage, so there is an interest to raise voltage, within limits though.
This is why, it is very important to reach the optimal setting for the current limit.

Also, The need for 24v power supply is often indicated for 3D printers, because the heated bed requires significant power, and higher voltage reduces needed current.
It is wise to get a power supply able to deliver twice the nominal required power.
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JeanePittman
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Re: Why a 24Volt Power Supply?

Post by JeanePittman » Sat Sep 22, 2012 6:39 am

So the higher the voltage, the faster the choppers can fill up the motors; the end result is more torque.
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loopingz
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Re: Why a 24Volt Power Supply?

Post by loopingz » Sun Sep 23, 2012 3:01 pm

My 24V PSU was fried on opening... I have got availablea solid 12V and laptop 19V 4.7A.
Can I use this one to run my test? Or should I wait for a working 24V PSU?
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

fito
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Re: Why a 24Volt Power Supply?

Post by fito » Sun Sep 23, 2012 5:41 pm

I'm using an old computer psu putting out 12V and it works well.
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loopingz
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Re: Why a 24Volt Power Supply?

Post by loopingz » Sun Sep 23, 2012 6:59 pm

Without touching anything to the settings (like max amp) I have X Y working fine. Z I am still strugling, too much drag I guess, I just have 'clac' noise. The good thing is that my power supply as the same plug so it is an easy temporary solution.
Shapeoko 1. Dual Y 1m with Name 17 (twice lower torque as the original motor). Double Xrails side to side. Acme-Z. Metalspacers.Wood 22mm waste board. Kress1050 with custom holder. Arduino GRBL + GRBL shield.

PsyKo
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Re: Why a 24Volt Power Supply?

Post by PsyKo » Sun Sep 23, 2012 10:45 pm

Hello,

Is it possible to use this power supply ?
http://radiospares-fr.rs-online.com/web ... s/6802802/

Or this one ?
http://fr.farnell.com/tracopower/txl-10 ... dp/3811955

I think they should fit, but I just want to be sure.
Any avantage to chose one over the other ?

Thanks in advance
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