Re: [CAD_CAM_EDM_DRO] Re: G201 modifications/update (P.S.)

ballendo@... wrote:

> Mariss,
>
> My comments in this thread concern what to do when an EMERGENCY
> situation presents itself. I will gladly trade a drive for a flying
> tool bit(and the damage it can do to a person)or "sliced" finger
> EVERY time.

I was also describing what to do for this. Since there are pulse
counters and
PLLs in some of the stepper drives, it is possible (but not really
likely) for them
to run away due to noise or a failed chip. Interrupting DC power from
the
main DC supply, and connecting the supply input terminals on the drive
to a dump resistor that is sized for the motor and drive would be the
best
thing to do. I use a similar circuit on my servo amps (this is not IN
the
servo amps, it is external, and one circuit powers/dumps all the axes.)
See the 6th picture (and text) at
http://ascc.artsci.wustl.edu/~jmelson/EMC.html
for more details.

The resistor value should be determined by figuring out the worst-case
developed voltage of the stepper at its highest speed, and dividing by
the driver's current rating. Too low a resistance value could cause
excessive
currents to flow, possibly damaging the drive or the motor. One detail
is to make sure the relays are sequenced to connect the dump resistor
before opening the connection to the DC supply. Leaving the drive
with no connection to a voltage stabilizing circuit could destroy the
drive.

Jon