Re: L298 goes boom - AWO?

Hi Tauseef,

Yeah, I lost track of the originator of the thread!

You WILL get an inductive "kick" if you disconnect it with current
running through it. That's in part how the ignition coil(s) in your car
work! OK, that and a little transformer ratio. Remember (those of us
old enough), when the points OPEN, that's when the spark is made (harder
to demonstrate on a car with "pointless" ignition.

I'd think it would be safe to disconnect with all windings off, but
that's just my opinion. It's been just as easy to (and probably a good
idea) to turn power off when switching motors around!

Now what I'm wondering, if the motor currents are off in either Gecko's
or a Camtronics board (or other L298 driver), is the circuit protected
against spinning the motor shaft (as in using a handwheel on the
tailshaft of the motor)?

I have tailshafts on my new motors (for shaft encoders, actually), and
I've been tempted to put on handwheels. Although I'm quite happy with
the jog controls I use from the controller program. Still, it might be
nice to be able to move an axis when the stepper is off, as when the
driver/PS box and the computer is not powered up.

Alan KM6VV
P.S. I'd vote for 2 or more switches! but then, I LIKE switches!

tauscnc wrote:

>
> Hey Alan,
> I started the post and have gotten some very good feedback. Seems
> there are some different viewpoints on EMF and unplugging motors with
> the power on. For me, I'll just turn the power off :)
>
> NOW::: can you unplug the motors if you have the AWO feautre on? The
> motors are already free? OR is this still an "EMF" problem?
>
> Thanks for the idea on the switches but on the camtronics board there
> is one AWO for all 3 axis (3 axis board) and another for the single
> board. I either need to fully integrate the hook up through the 3
> axis one to the single axis OR use one switch with two contacts (DTSP
> I think??). I ordered the parts today from Mouser and hope to get my
> goodies soon. Hope to have the camtronics boards working as flawless
> as they where since I started tinkering with them :)
>
> tauseef
>
> --- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> > Hi Lee,
> >
> > I might have Re'd the wrong message. The fellow I was trying to
> help
> > had a Camtronics board. I was trying to extrapolate Mariss' fine
> advice
> > to Dan's fine board.
> >
> > I don't know WHO the originator of the message was now! Were you
> also
> > replying to a message? I'm lost!
> >
> > Alan KM6VV
> >
> >
> > studleylee wrote:
> > >
> > > Hi Alan,
> > > I've never used L297/298's. On my G210's I'm running 75vdc. With
> > > 470uf Caps right at the supply pins of the G210.
> > > -Lee
> > >
> > > -In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> > > >Hi Lee,
> > > >What motor voltage are you running? I think I recall 37V being
> about
> > > >the limit for L298's.And I recall Mariss saying that caps across
> his
> > > >Gecko's were needed if working near the max voltage.Perhaps this
> > > >also applies to Dan's boards (see previous discussions on list)?
> > > > HTH
> > > > Alan KM6VV