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

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
>