A simple RC filter possibly combined with voltage division will remove noise 
although it will also reduce accuracy.

I think low input impedance will fix the problem with noise because even though 
voltage may be high only a limited amount of current may be transferred by 
capacitive coupling or an electric field.


Nicklas Karlsson
Micropower




On Thu, 30 Jul 2015 08:02:45 +0100
Marcus Bowman <[email protected]> wrote:

> 
> On 30 Jul 2015, at 03:51, Gene Heskett wrote:
> 
> > I bought a bag of small, roller tipped microswitches, and have a couple 
> > mounts laid out but not carved yet.
> > 
> > Going thru searches on ebay just now, for both inductive, capacitative, 
> > and IR proximity switches, It sees like the majority of them are needing 
> > 6 volts or more, and around 300 ma each to function.  Having seen some 
> > micropower capacitative switches in the textbooks of yore, it seems like 
> > the ball has been dropped in terms of being useful in a 5 volt logic 
> > circuit.
> > 
> > Both the microswitch, and the inductive versions would seem to be 
> > sensitive to collecting swarf, particularly if its a rare earth magnet 
> > running a reed switch.
> > 
> > My lathe seems to be relatively happy with a microswitch located under 
> > the back edge of the bed for Z homing where swarf tends to fall on past 
> > it, but x has to be kept swept clean because its actually on top of the 
> > carriage.
> > 
> > I see a whole passel of stuff drilled onto GO704's in the hits I can get 
> > from google, but all of them preclude retaining the rubber swarf 
> > shields, which I'd say was not worth the tradeoff.  There has to be a 
> > better way.
> > 
> > So what sort of switches, and what swarf shielding to keep them 
> > relatively clean & accurate are others using?
> > 
> > PM's with pix appreciated if you have the time.
> > 
> 
> Actually, this is a really interesting question. Having spent ages thinking 
> about shielded locations for the mill, and about to do the same for the 
> lathe, it would be useful if folks could put the pictures somewhere we could 
> all see them.
> If anyone has any recommendations about makes and models of switches/sensors 
> which provide better accuracy and repeatability than others, or useful ways 
> of providing adjustment on mounting arrangements, that would also be very 
> useful.
> 
> Marcus
> 
> > Thanks.
> > 
> > Cheers, Gene Heskett
> > -- 
> > "There are four boxes to be used in defense of liberty:
> > soap, ballot, jury, and ammo. Please use in that order."
> > -Ed Howdershelt (Author)
> > Genes Web page <http://geneslinuxbox.net:6309/gene>
> > 
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