The best stepper driver??? was Re: Stepper questions

Hello,

One of the first thngs I do with both xylotex and HCNC drives is to
replace the electrolytics with larger value parts...

Ballendo

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

>
> Actually there is another, more significant effect. The most

common

> drive failure report with low voltage drives is "The drive popped
> when I was decelerating my motor" or "The drive popped when my

motor

> stalled during a rapid".
>
> Step motors are unique in that can develop a back-EMF much higher
> than the supply voltage.
>
> For your own personal edification, chuck-up a 1A, 5V NEMA-23 motor

in

> a drill-press, Put a multimeter set to AC volts across a winding

and

> run it up to 2,000 RPM. If you don't read over 100VAC (141 volts
> peak), I'll eat my hat.
>
> Yet you can put the same motor on a 24VDC powered drive and easily
> spin it up to the same 2,000 RPM no problem.
>
> What happens? When you stall the motor, the kinetic energy stored

in

> the moment of ineria is released and returned. It gets returned to
> the drive as a current source with 100V+ of headroom. The power
> supply capacitor absorbs this energy at the expense of a voltage

rise

> across it. If the rise is enough, it exceeds the breakdown voltage

of

> the drive and pops it.
>
> Sound familiar?
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "jeffalanp" <xylotex@>
> wrote:
> >
> > Hi,
> > The largest cause of 3977SED drives "popping", when a SLA7062
> will
> > not, is when a person disconnects a motor when it is under

power.

> As
> > noted, the 3977 drive chip is specified for a max of 35VDC. As

has

> > also been stated in earlier post of this topic, when you

disconnect

> a
> > live motor wire you can get high (double?) voltage produced.
> > Running a 3977SED at about 30VDC would yield a voltage of around
> > 60VDC. Very bad for the chip. On the other hand, the 7062 MUST
> > handle the double voltage rating to cover the disconnected
> > transistor, because that is how unipolar drives work. So, the

guy

> > who innocently (or not so) blows up his 3977SED wouldn't even

know

> he
> > did something wrong with the 7062. There is nothing wrong with

the

> > A3977SED chip if it is run in its safe operating area. THE
> *absolute
> > largest reason* drives blow up is because people get excited at
> > trying the new hardware, don't follow instructions and do

something

> > wrong. Allegro makes thousands and thousands of these chips.

Most

> > probably go in to commercial devices like printers. These NEVER
> blow
> > up because they aren't subjected to undue stress (like

disconnects

> or
> > shorts or miswires or overheating, or...).
> >
> > The other main cause of a 3977 "popping" is when there is an
> > overcurrent. This can be from miswires or short circuits. I

don't

> > think the 7062 is immune to short circuits either. Since I

started

> > selling the 269 oz.in. motors along with the power supply and

drive

> > board in a "system kit", "blow ups" have dropped even more,

since

> > people are not guessing at how to make motors connections or

power

> > supply connections; I provide instructions with each.
> Unfortunately,
> > people STILL don't read these sometimes, even though they are

taped

> > directly to the device :-(
> >
> > Anyway, both drive chips are good devices when properly
> operated.
> > The 7062 may however be more robust to user error than the 3977,

so

> > if you plan on making mistakes like disconnecting a live motor,

go

> > with the 7062. If you plan on following manufacturers

guidelines

> > either will be fine.
> >
> > Jeff
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> > <dave_mucha@> wrote:
> > >
> > > -
> > > > IMO the early xylotex were not as robust in actual shop use,

as

> > the
> > > > other two. There was also a noise problem in the step/dir
> inputs
> > > > which Jeff to my knowledge has fully corrected in present
> boards.
> > > > Saying they were not as robust may be an unfair assessment,
> since
> > > > their popularity meant a larger sample and response was
> presented
> > in
> > > > these groups where much of my NON-personal experience is
> gotten.
> > > >
> > >
> > > The A3977 chip is listed as 35 volts and 2.5 amps.
> > >
> > > as I understand, the drivers on the Gecko are rated at

something

> one
> > > the order of 100 volts, but the assembled unit has a

manufacters

> > > rating of only 80 volts. a 20% de-rating of the components.
> > >
> > > In the early days of the Xylotex, many people tried to supply
> near
> > 35
> > > volts and with any back-emf, 36 volts was all to common.
> > >
> > > I find fault in the understanding of the parameters of the

chip

> and
> > > Xylotex has since, as I understand, recomended 24 volts as the
> > desired
> > > power supply.
> > >
> > > Dave
> > >
> >
>