Re: Caps over Sherline spindle.. doesn't work...

The Sherline and many other controllers for DC permanent magnet motor
controllers utilize back EMF to sense speed. Adding large capacitors
will confuse the controller. If you are going to use capacitors, they
should be 0.01 uF or smaller.

Another useful technique is to utilize a ferrite choke around the
motor leads. Typically these are 3/4" to 1" in diameter and 1" long
or more. The easiest to use are the ones that are split into two
halves that can be separated to put them around the cable. Use a
single choke core around all conductors of the motor cable. Sometimes
these can be salvaged from the keyboard or monitor cables of older
personal computers.

Good luck,
Steve Stallings
www.PMDX.com

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Abby Katt
<cncgroupnospam@s...> wrote:

>
> Well, tried it and.. well, it doesn't work.
> No smoke, but rather scary: I started with the motor down on low

speed,

> turned it on.. it ran really slow for a second, then with a THUD

(and

> lights dimming) the motor raced up to maximum speed. The motor

seems to

> lock at max speed... of course, I didn't wait around like that. I

tried

> it again with the same behavior, then removed the caps and it's

still

> working.. which is good.
>
> So why didn't this work then? Does the Sherline speed controller do

some

> trickery with capacitance/resistance to compensate for heavy-cuts

and

> thus deliver more power when the motor is under load? If so, what

can I

> still get away with on this motor and caps? Or is it a dead duck?
>
> Thanks guys!
> *confused*
> Abby
>