Re: My power supply calculations - Light Comes On

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ghidera2000"
<ghidera2000@y...> wrote:

> Actually, while sitting on The John* I finally clued into what Dave
> had mentioned about going by power instead of amps.
>
> If I had 5 volt 3 amp steppers thats only 15 watts. When I increase
> the voltage to 30, I still have to keep the actual power the same

or

> I have glowing/molton motors - so thats only 1/2 amp at 30 volts,
> not 3 amps at 30. Total power supply required for 4 axis would only
> be 2 amps, not 12...
>
> I've also been searching for Nema23 motors and noticing that most
> are below 5V. Paul Jones (CNC on a Budget) has 200oz/in Nema 23s
> that are 1.7v 3.4 amp. If I sized the supply for those I could drop
> the voltage to 20ish and still have them zooming along nicely.
>
> 1.7V x 3.4A = 5.78 watts
> 5.78 watts/20 volts = ~0.3A
>
> A 2 amp 14VAC transformer would be plenty for those motors. If I
> went for 4 amp, that'd be more than enough for any motors I'd

likely

> be using for PCB milling.
>
> Now the cap can be 80,000 * 5 / 20 = 16,000 uF - Closest being
> 18,000uF @ 25v but I'd go 35 cause I'm paranoid :D
>
> Of course I still have to see what size transformers and caps I can
> get around here for the exact ratings. But I'm still down to the

$40

> CDN range instead of over $100.
>
> * "The John" is a patented human intelligence boosting device. All
> rights reserved etc.

I wish I could take credit for the realization of watts, but
J.A.Roland was the one whom edumacated me on that a few months ago.
post 61226.

You may want to pull the laptop in to the john..... since you cannot
fire 100% into the motor, you cannot use all the power supply. you
can safely derate it to 66% of your simple watts calculation.

And yes, the John helps you get the crap out of the way so you can
think clearly !

Home Depot has 16 Volt 10VA doorbell transformers in case you are
interested.

and, go for the 50V caps. if you are like the rest of us, at some
time you'll get the hankering to tweek just a little more out of the
system. : ) also, shipping will more than likely be higher than the
cost difference.

Dave