Re: [CAD_CAM_EDM_DRO] Motor Noise?

Hi Sven,

Yeah, you need either sintered or ferrite. Oftentimes you can keep RF
out of stuff by getting an old TV deflection yoke, and wrapping turns
around that!

Lets see, if you're trying to "keep the RF in", then one can usually
turn on a TV or radio, and see what "works" (add a few beads, try a few
toroids). To keep RF out of a circuit is a little tougher. What wires
go into/out of the "box"? DC power lines can be bypassed with caps,
beads/toroid chokes can be added, and then you somehow need to get a
'scope probe in to see if RF is getting in. A little harder. Perhaps a
bulkhead BNC, with a short wire "probe" antenna INSIDE the box; to
couple out some signal to a 'scope. Check out the "ARRL handbook",
there are chapters on shielding and filtering, and probably some
suggested values of parts.

If you have the power supply inside the box, then try a CORCOM filter on
the AC leads.

There should be some data sheets on the Amidon products on the web
sites, these will give you the freq. ranges for the various beads and
toroids. Or call them!

Hope this helps!

Alan KM6VV


"Sven Peter, TAD S.A." wrote:

>
> Hello Alan,
> Thank you for the link, but it seems to me that I will first
> have to find out about the theory of blocking RF signals (1,3 to 1,5MHz
> and its harmonics) from the 60Hz lines (120V 10mA switched input for
> mini-PLC) I have to protect.
> This link is for me in chinese, I don't understand a bit from it!
>
> I remember in the radio and RF-amplifier factory I worked for that to block of
> a picked up signal you simply passed the wire some 2 or 3 times through
> a small bead that had several holes in it.
> Can't that be a simple piece of iron you drill in the holes?
> Or must it be the sintered stuff?
> Thanks for any response
> Sven Peter
>
> Alan Marconett KM6VV wrote:
>
> > Hi Sven,
> >
> > Try Amidon, who makes them, or a distributor:
> >
> > http://www.bytemark.com/amidon/content1.htm
> >
> > My local "Halted Specialties Company" (HSC) in Sunnyvale, CA has a
> > selection of them. Also check at "ham" supply houses. Digikey?
> >
> > Alan KM6VV
> >
> > "Sven Peter, TAD S.A." wrote:
> > >
> > > Where can you get ferrite beads or how can you make them.
> > > I have an application where I fear to get 1,5 MHz radiation into
> > > the mini PLC. I haven't seen ferrite beads for years and have no
> > > supplier for them. (asked already all local electric and electronic suppliers)
> > > Any answer is very appreciated.
> > > Thanks
> > > Sven Peter
> > >
> > > Alan Marconett KM6VV wrote:
> > >
> > > > Hi Phil,
> > > >
> > > > You might try some of the "clamp-on" ferrite cores used for computer
> > > > cables. At the speed control, at the computer parallel port cable, at
> > > > the driver, etc.
> > > >
> > > > Alan KM6VV
> > >