Re: [CAD_CAM_EDM_DRO] Worry, servo back powering Gecko

Hi Jon, Mariss, list,

Talk about back EMF! I was fooling around with a pair of #34 SloSyn
steppers, they had molex plugs on them, one male, the other female, and
I jokingly explained to someone that they were made to be plugged
together. Well I did, and spun one of the motors, and the other one
turned! I'd say there's something there!

Alan KM6VV


Jon Elson wrote:

>
> Roger Swift wrote:
>
> > When I manually position my servo mill (Tree Journeyman 350) with power off
> > the servos generate enough power to light up the Gecko 340's fault lights.
> > The table servos are large (rated 20 amps @ 90 volts) and connected through
> > a 3:1 reduction. The mill has both hand wheels and servos.
> >
> > Do I need to worry about frying the Gecko's? Do I need to put in a relay
> > between the Gecko and motor or remove the hand wheels?
>
> Obviously, Mariss can answer this better than I can, but this is a fairly
> normal condition. Any time the motors are moving with the servo drive
> disabled, there is pretty much the same effect. This happens any time you
> have to hit emergency stop while the machine is in motion. If the servo
> drives were to be damaged when you needed to hit emergency stop, that
> would be not only a poor design, but a dangerous one.
>
> The only way this could cause a problem is if the power fet driver chips
> were not properly biased under this condition. But, it is too easy for
> this to occur in other circumstances, so removing the handwheels is
> not really solving anything. Hopefully, Mariss can assure you there
> won't be any harm.
>
> Jon