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Old Oct 21, 2003, 12:00 AM
Bruce and Angela Dealhoy
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[EFLT] Use of capacitors to reduce RF noise for brushed motors

This message from "Bruce and Angela Dealhoy" <bdealhoy@sympatico.ca> brought to you by EFLIGHT!

Can someone please go over the whats and wherefores of using capacitors to
reduce noise on brushed motors.

I've got an Astro 15, and need to know what I should be using and how to do
the best possible job in setting it up.

Thanks!

Bruce


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Old Oct 21, 2003, 12:00 AM
Ray Carver
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Re: [EFLT] Use of capacitors to reduce RF noise for brushed motors

This message from "Ray Carver" <carver@c-zone.net> brought to you by EFLIGHT!

Bruce:
I use 3 capacitors. One from positive to ground ,one from negative to ground
and the third one goes from positive to negative. That works for me !

Ray Carver
Shasta,Ca.

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----- Original Message -----
From: "Bruce and Angela Dealhoy" <bdealhoy@sympatico.ca>
To: <eflight@ezonemag.com>
Sent: Monday, October 20, 2003 6:08 PM
Subject: [EFLT] Use of capacitors to reduce RF noise for brushed motors


> This message from "Bruce and Angela Dealhoy" <bdealhoy@sympatico.ca>

brought to you by EFLIGHT!
>
> Can someone please go over the whats and wherefores of using capacitors to
> reduce noise on brushed motors.
>
> I've got an Astro 15, and need to know what I should be using and how to

do
> the best possible job in setting it up.
>
> Thanks!
>
> Bruce
>
>
> *** Any complaints or problems? Send an email to monitor@ezonemag.com
> *** For help with list commands go to

http://www.ezonemag.com/pages/mailhelp.htm
> *** For the list rules go to http://www.ezonemag.com/pages/mailrule.htm




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Old Oct 21, 2003, 12:00 AM
Stephen & Janice
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Re: [EFLT] Use of capacitors to reduce RF noise for brushed motors

This message from "Stephen & Janice" <stevnjan@ils.net> brought to you by EFLIGHT!

Oooooooooooopppppppppppssssssssssss!

Supposed to go to Bruce!

Stephen


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Old Oct 21, 2003, 07:01 PM
Doug Ingraham
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Re: [EFLT] Use of capacitors to reduce RF noise for brushed motors

This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Mon, 20 Oct 2003 AZSPYDR@aol.com wrote:

> In a message dated 10/20/2003 7:03:50 PM Mountain Standard Time,
> bdealhoy@sympatico.ca writes:
>
> > Can someone please go over the whats and wherefores of using capacitors to
> > reduce noise on brushed motors.
> >
> > I've got an Astro 15, and need to know what I should be using and how to do
> > the best possible job in setting it up.


You can actually make the situation worse if you do this incorrectly. The
Astro motors come with the correct caps installed. I believe Astro uses
0.22uf ceramic types with an appropriate voltage rating. You want to
connect a cap from each terminal to the case of the motor. This
arrangement tends to short the noise into the case of the motor which
tends to have the properties of a Faraday cage when done properly. You
want the leads of the caps to be as short as possible and the caps should
connect to the case at the same point. Addition of a third cap between
the motor leads is sometime done but I have never understood why this is
thought to be necessary. Twisting the leads between the motor and ESC
will also tend to reduce noise and is almost free to do.

> I dont have the answer but I do have an additional question which is
> relevant. Most ESCs, and some motor manufacturers specify a Shottsky
> (sp?) on the motor--but not Astroflight---I have just installed one+ the
> other two 'regular' ones. . Any comments on the necessity for a a
> Shottsky?? Ted in AZ recommend


You need some method of restraining the energy that comes back out of the
motor when the drive FET is switched off. With 7 cell packs I have seen
150 volt spikes come back out and this tends to destroy the 30 volt rated
drive FET instantly. There are several approaches used in the speed
controls all of which work to greater or lesser extents.

>From approximatly worst to best (although nothing is really wrong with any

of them when used within design specs).

Body diode in the Brake FET
Ultra fast rectifier on the ESC.
Ultra fast rectifier across the motor leads.
Schottky diode on the ESC.
Schottky diode across the motor leads.
Synchronous rectifier circuitry.
Synchronous rectifier circuitry with addition of a Schottky in the ESC.
Synchronous rectifier circuitry with addition of a Schottky across the
motor.

Not so amazingly this is least to most expensive and complicated.

Doug Ingraham
Rapid City, SD USA




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