Power Supply

[AYahoo]

Hi, I have a newbie question.

I have 3 stepper motors with these settings 1.06 A 3.18V bipolar 1.8° (Micro mill).

I need power supply for it, how do I calculate the total power I need, do I need only - 3 X 1.06 = 3.18A and 3 X 3.18 = 9.54 V?

And what do I need regulated power supply or not? will a power supply of a computer will fit? (12V, 8A)

Thanks in advance,
Asaf.

[Jarwalcot]

See Attachment..

Have a great week,

[AYahoo]

Hi, THANKS for the fast replay, and Have a GREAT week also

Sadly your attachment didn't help me with my question; it doesn't mention the solution for it.

Thanks again thou,
Asaf.

[thkoutsidthebox]

I can only try to help from my own limited experience.

My HobbyCNC 200oz/in motors each draw 3A and 3V. Im using three (3) of these and I required a power supply with a minimum of 12VDC and 10A.

Therefore, I think that your 12V 8A supply should be fine, but mine are unipolar, and I dont know what differance bipolar would make if any. You can supply amps until the cows come home, e.g: Have a 50Amp supply, but your motors will only use from that 50 whatever they need so no point going that high, but be careful with the voltage, because if its too powerful then you'll see the magic smoke escaping .

[Torchhead]

The voltage for steppers is a function of how fast you want to charge the coils. The faster you charge, them the faster they turn. General rule of thumb is from 10 to 25 times the nameplate voltage.

All of this assumes a modern chopper (current limited) motor drive that controls the current to the motor.

The limiting factor for voltage is often the motor drive itself so you can't always furnish the optimum voltage. For you motors something like 24 VDC would provide moderate speeds and 48 would be better (but probably mean going to more expensive drives).

Motors are power devices and the output is in watts (or HP or BTU's, etc) which is derived from the voltage X current across a given impedence (of the motor). The drive controls the current on a pulse by pulse basis. The more voltage available the quicker the coil of the motor reaches the current and the waveform is turned off.

You will find average current goes down in a stepper system as the voltage goes up so for those small motors a 2A supply would be fine. If you are paranoid then 3A.

Once again all of this is contingent on using Chopper drives with lossless current control. All bets are off on the older LR type drives that use external power resistors to control current.

Take a look at the Xylotex 3 and 4 axis stepper drives. They run well on 24 volts. They are bipolar and chopper current controller drives.

Also check my website for integrated electronics solutions for desktop CNC.

There has been a long debate about using switching or linear (unregulated) power supplies. On smaller motors we have been using switching power supplies with no problems. At the most we have added a filter cap to the output of the switcher to deal with the non-linear current draw of motors.

I think conventional supplies (50/60 hz magnetics) are a better solution for larger systems and bigger servo drives.

You find on small mills with fine pitch leadscrews that you have plenty of torque with small motors but can't get decent feedrates. You can expect about 150 RPM out of your motors at 12VDC, and with a 20 pitch leadscrew that translates to about 7 IPM max. You want to try and operate steppers while you are cutting, and you need the torque, at 50% or less of the max RPM so you cut speeds are now down to 3 IPM. By doubling the voltage you can make this other numbers go up.

Steppers lose torque as their RPM increases. Just a nature of the beast.

Tom Caudle
www.CandCNC.com

[AYahoo]

Hi All,
First let me thank you all for the interesting replays.

I'm using - 3DStep controller with this tech details,

3 channels (expandable to 4)
Easy adjustable phase current up to 2,1A per phase (via trimmer)
Up to 45V supply voltage
TTL compatible in- and outputs
Connectable to PC printer port or microcontroller
Compatible to common CNC software (PCNC, CNC-profi, DIN-CNC, Mach2, EMC etc.)
Half- and full step mode
Two different current regulation modes
Onboard logic for 4 reference/limit-switches and one emergency switch
Connector for status LEDs or 4th axis extension
Adjustable chopper frequency
'Smoothing' function for more torque in half step mode
Typical current consumption 250mA (5V part)
Suitable for both bi- and unipolar stepper motors with minimum 1,6 ohms coil resistance
Eurosize board (160*100mm)

As I understand from Torchhead post, since I'm using the controller.
That the Amp is not a problem - (since 2A is small amount of Amp) then I need a bigger Voltage, you said 10-25 times, that means (10*3 = 30) - (25*30 - 750)????

I live in Israel, and the price of the power supplies here are expensive. So I would like to use one of a computer. I know that it is regulated, will it be better than not regulated?? And I have only 12V. So I need to think about modifying it....

So basically a good setup will be 3Amp 24Volt?
is that right.

Thanks.
Asaf.

[AYahoo]

I found a 2Amp 24V Unregulated power supply, will it fit me?


Thanks.
Asaf

[Jay C]

Originally Posted by AYahoo I found a 2Amp 24V Unregulated power supply, will it fit me? Thanks. Asaf

No. You need to supply the minimum total current. 3 X 1.06 = 3.18A

[AYahoo]

Hi, Thanks for the replay. I understood that it wont fit me

I'll try using 2 PC power suppliers.

Thanks,
Asaf.