Re: Voltage to steppers

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
<mariss92705@y...>" <mariss92705@y...> wrote:

> Stan,
>
> I like the way you think. Being inventive is to simply look a

problem

> from an unconventional perspective.
>
> Rather than limiting current (a current source takes care of that

all

> by itself), is to vary the supply voltage the current source has to
> work with. That is something you can predict based on the "steps

per

> second".
>
> What you are proposing is a closed-loop feedback to prevent the

motor

> from stalling by adjusting the power supply. That is a good idea.
>
> Unfortunately it requires overly complex circuitry to accomplish; I
> know because I spent some time with the idea before I abandoned it.
> The competing concept was to simply "brute force" it by having a

high

> voltage present at all times. Can't beat a simple solution,

imperfect

> as it may be.
>
> Mariss
>
>
>
> > Hi,
> >
> > It occurred to me that if the controller program kept track of

the

> > steps per second, it could also predict the current needed from

the

> > power supply.
> >
> > Also, one could write the controller program to limit the current
> > needed from the power supply by limiting the steps per second.

When

> > the steps per second approached the limit, the program could
> stretch
> > out the clock period such that the issuing of step pulses to the
> > stepper motors is slowed uniformly.
> >
> > Is this in any controller program?

Mariss,

I left out the motivation for the above. I need a power supply
for some steppers. Worst case, I should allow for all 3 or 4
steppers running at max steps per second. However, if the
controller could limit the current used by limiting the steps
per second, then I could likely get by with a significantly
smaller power supply, like 50% less current.

My stepper model is that for each step, there is an almost
linear ramp up to maximum current in a winding, then followed
by a chop mode. For the linear ramp, the current average is
50% of the maximum winding current. And for the chop mode,
the current average is say 10% of the maximun winding current,
assuming that the power supply voltage is say 10 times the
voltage needed to get maximum current in the winding.

Intuitively, I guessed that limiting the steps per second to
say 1.5 times the max rate for one stepper, would degrade
real world performance slightly, and allow using a smaller
power supply.

Newbie Stan