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Author Topic: Noise - Aluminium foil screen? - Faraday Cage?  (Read 2562 times)

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Offline newatcnc

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Noise - Aluminium foil screen? - Faraday Cage?
« on: July 01, 2012, 04:15:00 AM »
Hi
I am running my Sherline mill with a G540 driver and apart from occassional false e-stops everything is great.
False E-stops are becoming more frequent though. This is my only frustration with this set up.
Limit stop wires are in the same cable as the stepper motor wires and no screening so this is an area for immeadiate improvement.

I ran a 3 hour g-code without the spindle running and no problems, the same g-code with the spindle running gave several false e-stops, (strangely occasionally at the same g code lline!).

Not being knowledgable about such things it would seem the motor and/or it's controller are causing noise problems. (It's a DC motor with brushes)

I was wondering if I wramp the cables in alumimium foil or tape and earth this is it suitable screening? (I will re-route the limit switch wires separate from the motor wires)

Also I was wondering, if I were to put the controller in a Faraday cage, would it help? Anyone done anything like this? or is it just silly?
I would think a Faraday cage could be made from steel mesh and earthed. I know Faraday cages are used in high voltage areas to protect equipment, not sure if it's applicable here.

Additional info if applicable:
Power supply and G540 are in an enclosure together with an e-stop switch and cableing- there is no other E stop switch.
Enclosure with controller is within 2 to 3 ft of the mill.

Any comments appreciated.

Cheers
Nigel
Re: Noise - Aluminium foil screen? - Faraday Cage?
« Reply #1 on: July 01, 2012, 04:26:42 AM »
make sure your ground correct or not/ may be because of groung this kinds of noise generate.

Offline RICH

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Re: Noise - Aluminium foil screen? - Faraday Cage?
« Reply #2 on: July 01, 2012, 09:12:13 AM »
Nigel,
Shielding may keep noise / an offending magnetic field in or out. Sort of like a tube which keeps water inside or outside water from coming inside the tube. Shielding can be different %'s, wire meshes or braiding are have a basis for use. Maybe save yourself some agrivation and just replace the wiring with shielded cable. You will find 100% will have both a foil wrap and also
a braide. The ground provides an easy path for the noise or  interference to travel and should be an independant ground system.

RICH


 

Online Tweakie.CNC

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Re: Noise - Aluminium foil screen? - Faraday Cage?
« Reply #3 on: July 02, 2012, 01:41:57 AM »
Hi Nigel,

Re-wiring your limit switches (separate to your motor cables) using shielded cable (with the shield grounded at the controller end only) is the best way forward in curing your problem of the random stops.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline newatcnc

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Re: Noise - Aluminium foil screen? - Faraday Cage?
« Reply #4 on: July 03, 2012, 11:48:34 AM »
Hi Everyone
Thanks for your help and advise.
It ran 4 hours continuous at the weekend without a hitch but this evening I had continuous false e-stops, sometimes several within as many minutes.
So re-wiring with sheilded cable is now my urgent priority.

Thanks again
Nigel