## Power Supply

PLHS54
Posts: 60
Joined: Sun Apr 22, 2012 7:36 pm

### Power Supply

I know the wiki page says:

"The size of the power supply should be at least 4.2A at 24V. A larger supply (for example, a 4.5A) will work fine. The size is based on the requirements of the stepper motors you choose."

I'm interested in two things. First, what is the mathematical formula for figuring out the amperage you power supply needs to deliver based on your stepper motors? Second, will an AC 100-240V to 24V DC 5A 120W Regulated Switching Power Supply work with the stepper motors from Sparkfun listed on the wiki parts page?

Thanks,
Michael

pourcirm
Posts: 44
Joined: Mon Apr 09, 2012 6:25 pm
Location: Saint Louis, MO
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### Re: Power Supply

A 24 Volt 5 Amp supply should work fine with the Sparkfun motors. It's actually even better than the power supply that the Inventables kits are shipping with and I believe they are using the same Sparkfun motors.

I'm not sure about the best mathematical formula for the current, but maybe someone else can help you there. From what I've read in general the current you need/will use is more dependent on the motor drivers you plan on using. Generally you need to adjust the current from the motor driver so that it doesn't overheat and miss steps or go into thermal shutdown.

The other thing to know is this:
When the motors are being driven they're turning on and off very quickly, and are acting somewhat as a step down power supply. So even when the drivers are set to 2A, and the motors can say take 3A, you'll actually only be pulling about 0.6 - 0.8A / stepper.
- Edward
The motors operate in a way that keeps the current level down so your motor shouldn't reach the maximum current that it's rated for. It's actually pretty complicated how the stepper motors work and I don't know the best way to explain it truthfully.

So the short answer is yes that supply should work.

Paul.Rodgers
Posts: 1
Joined: Sat May 12, 2012 10:05 pm

### Re: Power Supply

I was wondering about the 24v requirement
I'm looking at some NEMA-23 steppers, pulls from older equipment.
On the stepper case it says 6v 1.6-degrees/step, they are japan-servo KP56-LM2

so: why do I need 24v? Th PS in the equipment they came out of is marked 12v, 15A, and 5v 30A, looking these up I think they are rather stronger, but not as accurate.

will this run a shapeoko? the Arduino certainly doesn't need 24v, does a GRBLshield require it?

or Am I just bettor off ignoring my instinct to recycle older junk and but a new PS and some new steppers?

LineKernel
Posts: 65
Joined: Sun May 20, 2012 11:42 am
Location: France-Avignon
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### Re: Power Supply

@Paul.Rodgers

hi , from what i read on the spakfun comments at this page http://www.sparkfun.com/products/10847 , if you look up for Jagrolet s answer , it seems that you have to put a tension (Volts) between 5 and 20 times the one from you motor specs ,
the driver is then used for limiting the intensity (Amps) at the max of your motor specs (or it ll die)

12v, 15A, and 5v 30A,
seems huge . but it doesnt say anything about accuracy (in degre or number of step per turn)

the arduino will not take 24 V (i think 9v or 12v max , not sure about 12v but 9 for sure works i have tryed )
this 24v power supply is plugged in your GRBLshield in the "screw header" (green from the picture i see on the website)

the electronic on the GRBLshield is power from the arduino ,
both circuits are kinda separated

RibbyPultz
Posts: 8
Joined: Thu May 24, 2012 2:57 pm

### Re: Power Supply

I realize this may be a very basic question but does anyone have a recomondation on the type (size, guage etc.) of wire to use to connect the power supply to the grblShield?

Thanks.

aldenhart
Posts: 132
Joined: Tue Apr 10, 2012 2:17 pm

### Re: Power Supply

The best wire gauges for power are 20 ga or 18 ga. Anything larger than this (16 ga or smaller number - the numbers get smaller as the current handling capacity gets larger, until you start using 0 and 00 and 000) is also OK, but the larger gauges get hard to connect to the terminals as the wire size gets bigger. 20 ga is capable of about 4 amps, plus or minus, 18 ga. is 7 amps plus or minus, and 16 ga is 10 amps +/-. 22 ga is also possible, but I'd say it's marginal.

The same wire used for the power connection can also be used for the motor connection. I usually look on Ebay for 4 conductor shield "AV" wire in 20 or 18 ga.

-- Alden

PLHS54
Posts: 60
Joined: Sun Apr 22, 2012 7:36 pm

### Re: Power Supply

aldenhart wrote:The best wire gauges for power are 20 ga or 18 ga. Anything larger than this (16 ga or smaller number - the numbers get smaller as the current handling capacity gets larger, until you start using 0 and 00 and 000) is also OK, but the larger gauges get hard to connect to the terminals as the wire size gets bigger. 20 ga is capable of about 4 amps, plus or minus, 18 ga. is 7 amps plus or minus, and 16 ga is 10 amps +/-. 22 ga is also possible, but I'd say it's marginal.

The same wire used for the power connection can also be used for the motor connection. I usually look on Ebay for 4 conductor shield "AV" wire in 20 or 18 ga.

-- Alden
This raises a question with me. You mention that you can use 18 or 20 ga wire for the motor connections. Looking at the datasheet for the sparkfun stepper motors, it says that the wires on the motor are AWG 26. Is there any need to worry about connecting 18 or 20 ga wire to this 26 ga wire?

Enraged
Posts: 230
Joined: Mon Apr 09, 2012 8:29 pm

### Power Supply

Aside from being a pain? If you use molex connectors at the motors, make sure you get the right pins for the wire size, as an 18g pin won't work well with a 26g wire

RibbyPultz
Posts: 8
Joined: Thu May 24, 2012 2:57 pm

### Re: Power Supply

I have one more question pertaining to the power supply. In the construction of an enclosure for my electronics I have come across a cooling fan similar to the one shown here to foster some air movement.

http://www.amazon.com/gp/product/B007PQ ... 00_s00_i00

My question is can the power supply handle both this fan and the stepper motors (via the grbl shield) or is this asking to much and will result in performance problems for the motors?

For reference I am using the power supply shown here.

http://www.digikey.com/product-detail/e ... 17?cur=USD

In looking at the specs on the website it says that it only has one output so I am guessing the odds are not in my favor. But in looking at the power supply there are two connections with V+ and two with V-. Can these connections power two different components and if not is there a difference between the pairs? Should I use one V+ terminal as opposed to the other?

Thank you in advance for helping out a noob.

edwardrford
Posts: 1250
Joined: Mon Apr 09, 2012 5:40 pm
Location: Dixon, IL
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### Re: Power Supply

I'm not an expert at this sort of thing (or anything really) but I think you will be fine running multiple 24v accessories so long as you do not exceed the maximum amperage your power supply can put out. My guess is the fan probably only draws .1A of current, leaving the rest available for your steppers.

The designation of single output on your power supply refers to only a single voltage value (24VDC) being outputted not the number of terminals. Most single output supplies have two sets of outputs. Both outputs putting out the same voltage. As opposed to a dual output supply, which might also have two sets of terminals, each giving off a different voltage value (ex: 5VDC and 24VDC). Make sense?

-Edward
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