Re: Router spindle electrical noise. SOLVED

Silly me I went and looked and the cables are indeed shielded after
all (it was a while ago that I wired them up). I had grounded the
shields at the controller end.

In any case I think I have solved the problem with a cap at the
terminal strip between the limits and ground. I ran the router for
15 minutes with no false trips. The most I could get before was a
minute or so.

Thanks all for the input.

Eric


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Dan Peirce <danpeirce@t...>
wrote:

> It appears there has been a consensus that this problem would be

fixed with

> shielded cable. It has worked for others.
>
> I would like to suggest a cheaper easier solution but I don't have

the CNC

> machine to test it on so I cannot guarantee it will work for you.
>
> First I am concerned with how you ran the wires to the three

switches.

> Schematics don't show such things. I would wire a twisted pair from

the

> control box to each of the three switches. In that case any noise

linking

> into one conductor would also link the paired one in almost exactly

the same

> way. The noise would therefore tend to cancel itself by the time it

was

> conducted back to the control box.
>
> My second suggestion would be to add a 50 ohm 1 W resistor from the

switched

> line to ground before the 4.7kohm resistor. The effect would be to

lower the

> impedance to ground and dampen induced noise. It will pull an extra

100 mA

> from the supply which I would expect could handle it.
>
> More effective still would be to use a optocoupler like the 4n25.
>
> By the way, the LED's are shown backwards in your schematic.
>
> On October 20, 2003 03:59 pm, you wrote:
> > Wow what a great response! I think I will try the easy stuff

first

> > so I will put a wee cap on the limit switch input to the breakout
> > board err/res manager.
> >
> > My breakout board is home made. See the circuit here:
> >
> > http://www.e-zflight.com/files/ncnczy.jpg
> >
> > gecko faults and the limits trigger the same input to pc, but the
> > gecko's are fine. External LED's indicate gecko status. There

are

> > actually 4 gecko's used, drawing shows two.
> >
> > Eric
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "balsaman_cnc"
> >
> > <balsaman_cnc@y...> wrote:
> > > The electrical noise generated by my Porter cable Router is
> > > triggering my limit switch circuit. The limits are high and go

low

> > > if there is a problem. They are all in series (NC). If I set

the

> > > speed on my router down 20% or so the problem goes away. I slid
> >
> > one
> >
> > > of those ferrite donuts over the limit switch cable with no
> >
> > effect.
> >
> > > Is there something else I can try? I used shielded cable on all
> > > cabling EXCEPT the limit switches...do I need to replace all

that

> > > cable? Are there other options?
> > >
> > > Thanks for any help you can provide.
> > >
> > > Eric
> >