Limit switch wiring question ...

[Lee Roberts]

Made me smile Jonathan thank you.

With regards to extrusion, if your going to do it, use shielded cables to do it. Im thinking that any noise that dose get in, may echo like sound in a tunnel, then you may get an echo of an echo and so on and so on, leading to an amplification? If the end of the tunnel is of a blind type, the noise cant escape ?

There maybe other complications to, access being the first to come to mind.

Lee

[Jonathan]

I'm not sure about echoing, but surely so long as the aluminium is grounded then any noise that does get in should go to ground quickly?

[Lionelectric]

Think of it this way, a shield is one end connected to earth/ground, an earth/ground is both ends connected to earth!

[ptjw7uk]

I am getting a bit confused here as I thought a limit switch could not suffer from 'noise' as its either open or closed switch.
Noise would be a problem if it got back to the drivers input etc.
A more pertinent question would be should the limit be open or closed switching, I think the best is to go open circuit so that a broken wire will stop the machine.
Just my 2p

Peter

[Robin Hewitt]

Hang on a mo'

All the limit switches are daisy chained together...

... you switch on and it shows closed...

... which way do you go? :rofl:

[Swarfing]

I think people are getting too hung up on this, where motors are concerned there will always be noise. The best thing to do is just wire them up and see if you have any interference? this can be dealt with by grounding shields, toroids or better quality cable. I use a single shielded cable and have no problems with it not being grounded. Most cases it is just to be aware that you MAY suffer and not that you will have? Ground loops can cause more issues than a bit of noise after all we are not in the days of valves and tubes anymore. Always look at routing cables away from the motors as best you can and keep it tidy. Just enjoy your build rather than frightening yourself over something that may NOT happen :-)

[Wobblybootie]

I like your thinking .... What is a 'Ground Loop' ??

[Swarfing]

LOL! get on with it

in a nut shell instead of leaking off your interference it returns via another path

[Robin Hewitt]

I like your thinking .... What is a 'Ground Loop' ??

When your earth wires form a loop, think of it as a single turn fat transformer winding that someone has shorted out with a crowbar.

It soaks up stray magnetic fields, sucking power out of anything trying to flow AC or switch DC. It flows milliVolts at big Amps.

The worst one is when a newbie looks for somewhere to connect his earth wire and spots a handy nut on top of a toroidal transformer :rofl:

[Robin Hewitt]

PS: RS232 serial is good for a hundred yards at 9600 baud so long as you use good old telecom twisted pair. Use screeened cable and you'll be lucky to get 25. There's a message there for wiring your limit switches, maybe? :naughty: