How can I calculate watts I need to be supplied?

Other Hardware Motors, Mechanics, Power and CNC
1

Dear All,

First of all, Sorry for my English, It's not my first language.
But I will do my best I can describe....

I'm a beginner about Arduino and any engineering, Electronic things
(I've been art Uni..LOL)
I recently knew about Arduino and really love to digging into it.
And I just started my personal project (making robot arms with Arduino).
I nearly finished it. And tested well.

But my question is..I'm not sure How much watts it need to be supplied..
I remember..voltage X Amp = Watts...

there are Arduino Mega and 1 DC motor, 3 survo motor, 1 nema 23 stepper motor, 2 nema 17stepper motor.

My calculation is...

Arduino Mega 0.27 watts
Dc motor 12V 13.57 watts (at max power)

3units servo motor(SG5010)
Can't find in datasheet..
I just assume 6V X 500mA...3 watts X 3units

2units Nema17 (17HS24-2104S)
I will supply 48V and 2A(DRV8825 driver) 96 watts X 2 units

Nema 23 (23HE45-4204S)
I will supply 60V and 4.3A(DM860T driver) 258 watts

And 2 LED and 4 Photo Resistor sensors.. And 2 hall sensors..
But those sensors are just need little amount of watts they need i think..
So i would like to add just few watts for it and in case of extension.

Also I will use 48V switch power supply with voltage regulator if I can..
the voltage regulator will be

And LM2596S..
(I heard that regulator need some power itself.)

472.84 watts + some extra...I can calculate

So can I supply with 48V switch power supply 600W 12.5A in max power?
Or need to concern any other power?
And If I change the voltage with regulator..will be any different method for watts??

I was thinking 1,000 watts one..But maybe it will be wasted money and power..

Could you advice for me?

Thank you for reading this and your time!!!
everyone read this, Have a great day!

2

Watts are almost irreverent, Just concentrate on the voltage and current you need to supply.

3

Thank you for your reply!

So...If I use a motor 12V 4A..
should I think it needs 4A or 1A from 48V power supply with regulator?
(disregarding the power for regulator itself)
can I divide current by voltage?

Sorry..This is barely first time to use it for me...
nearly no knowledge about electronic engineering...

4

If it is a switching regulator the current required to drive it will be less than 4A by a simple power calculation plus you need to add in the efficiency of the step down regulator. This is normally about 80 to 90 %. If it is not a switching regulator then you need the full 4A at 48V and then you waste all that extra voltage drop as heat. That is a hell of a lot of heat to get rid of, possibly it will be not possible. Do not worry about the power the regulator takes, that is all wrapped up in the regulator's efficiency figure.

5

thank you so much!
I can see one of my regulator is switching regulator..
And other one is Buck module...Seems like...It says 97% efficiency...
I can see there will be some noise but I will figure out! LOL!

Thanks a lot!

6

A switching regulator and a buck regulator are different names for the same thing.

7

Hi.

Sorry for my English.
I'm not sure you need 600w!

The big problem with electric motors it's startup time. I know that at startup the motor require more amperage to get from static position to full speed.

The startup amperage is a product of nominal amperage and startup time.

Ex: In = 2A and T = 1.3S
SI = In × T
SI = 2.6 A

I think with this equation in mind you can adjust you circuit power supply.

Not: this only apply for electric motors.

8

Not much help I am afraid :wink: But I have worked with Systems Engineering teams to help establish the power supply requirements for largish systems.
Usual start is to add up all the individual loads, which often gives a large power requirement as a starting assumption is that everything is operating all the time.
When that look implausible, deeper analysis is required to determine what is operating when and for how long.
If that still gives too large a demand then techniques to reduce consumption, e.g. motor soft start and reduce peak instantaneous current demands. These can be further eased by large (=very large capacitive reservoirs).
My experience is also that after all this the power supply equipment is often over specified. That gives an oppertunity to reduce cost - then the design team can get a bonus :wink:

9

Better to assume 1A per servo (6W each).

For a 'buck' or 'step-down' converter, your supply voltage has to be higher than the output voltage.

You won't get 60V out of that without a BOOST converter.

10

No, stepper drivers are switch-mode power converters, the power will be more like 10--30W for a NEMA23 though it will depend on the motor and how hard its being pushed.. The current from the supply will be much less than the current taken by the motor most of the time.

NEMA17's take maybe 6 to 15W or so.

11

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