Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Robhi on December 15, 2007, 06:55:19 AM

Title: Help about "24VDC/5.0A "
Post by: Robhi on December 15, 2007, 06:55:19 AM

Could I use a PS that is used for a printer for my:--

The XS-3525/8S-4 Stepper Motor Driver Board
The Perfect Choice For Your Sherline or Taig Four Axis CNC Retrofit

Four axis bipolar drive
±2.5 Amp/Phase PWM controlled drives
up to 35 Volt (w/BEMF)
FULL, HALF, QUARTER, & EIGHTH step/Full Step .

The PS that I would like to use is input 220 volte, output is 24VDC/5.0A .

I do not know if that would work.

any help of you will be appreciated.

Title: Re: Help about "24VDC/5.0A "
Post by: Hood on December 15, 2007, 11:36:23 AM
5Amps might just be on the low side depending on how many motors and their current ratings.
Title: Re: Help about "24VDC/5.0A "
Post by: jimpinder on December 15, 2007, 02:26:52 PM
If three motors turn on simultaneously they could sink 7.5 amps - way beyond the capabilities of your power supply. If you have four motors - 10 amps.

You could be clever and only run programs that do not move more than 2 motors at once - but ????

A simple way I have my power supply is from two 12 volt leisure batteries which I charge up now and then. The advantage with batteries is that the overall voltage is steady at 24 v (in series) , no matter what the current drawn way beyond the 10 amp mark. It is a bit expensive - about £80 (UK) but, I find, very simple.

I have the input protected by a diode bridge in case I connect them the wrong way round inadvertantly.
Title: Re: Help about "24VDC/5.0A "
Post by: Robhi on December 16, 2007, 06:01:15 AM

Hi, thanks for your replies.
the motor that i have are the followings:

220Ncm - 10mm Shaft - Hybrid Stepper Motor 

Arc Code   AC571157525M
Type   Hybrid Stepper
Holding Torque   220Ncm
Step Angle   1.8°
Rated Voltage   7.5V
Rated Current   2.5A/Phase
No. of Wires   8
Size   57x57x115mm
Shaft Dia.   10mm
Shaft Length (Front)   30mm
Shaft Length (Rear)   30mm
Net Weight   1.74kg

I would like to run the three of them at once ( as am not too clever to run only 2), they would be wired in bipolar parallel,
so as you said I might have a PS of 24VDC/7.25 Am or more.
Am I right?

Title: Re: Help about "24VDC/5.0A "
Post by: Hood on December 16, 2007, 06:31:46 AM
I think the accepted figure is 2/3 of the total motor current as you are unlikely to be using all 3 axis at full current at the same time. However I would still be wary of using a power supply that is borderline, best bet is to get yourself  a toroidal transformer, a rectifier and a capacitor and build yourself a power supply. Bob Campbell has a good pdf on how to work out the figure for the various components of a power supply, you will find it here

Title: Re: Help about "24VDC/5.0A "
Post by: jimpinder on December 16, 2007, 06:42:28 AM
You are using the same motors as I am. They work very well. I run mine on 24 volts, they get slightly warm but not hot, even when stood a long time.

Unlike an ordinary motor, a stepper motor comsumes power even when stood - the current keeps the rotor fixed in the one position. I think your 5 amp supply will struggle. You will find that the voltage output will dip as the motors take power. The Stepmaster cards I used at first carried a warning not to let the voltage drop below 12v, or everything would overheat.

Try it and see - start by using only two motors connected and see how the supply voltage holds up.
Title: Re: Help about "24VDC/5.0A "
Post by: Robhi on December 20, 2007, 02:55:01 PM
thankx  for replies, they are great and useful.
thankx again