From: Manu Abraham <abraham.manu@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Tue, 8 Dec 2020 11:58:35 -0800
Subject: Re: [EE] Eliminating external noise through PS
Thread-Topic: [EE] Eliminating external noise through PS
Thread-Index: AdbNnagNRwpEb9WESXimltyBSxmkZQ==
Message-ID:
 <CAHFNz9JupUezFtWeF4FDkmcjiVfuY57r0-07fH2thYsMtP6Qrw@mail.gmail.com>
References: <5FCFC00E.8040703@narwani.org>
	<CAHFNz9+v2Pj5fdHpMwuwYsvEWf9+Y_dyhw_ishHarRz9mnuEyQ@mail.gmail.com>
	<5FCFD705.2090703@narwani.org>
In-Reply-To: <5FCFD705.2090703@narwani.org>
Reply-To: Microcontroller discussion list - Public. <piclist@mit.edu>
Accept-Language: en-US
X-MS-Exchange-Organization-SenderIdResult: Pass
X-MS-Exchange-Organization-PRD: mit.edu
X-MS-TNEF-Correlator:
received-spf: Pass (protection.outlook.com: domain of gmail.com designates
	209.85.219.181 as permitted sender) receiver=protection.outlook.com;
	client-ip=209.85.219.181; helo=mail-yb1-f181.google.com;
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com;
 s=20161025;
	h=mime-version:references:in-reply-to:from:date:message-id:subject:to;
 	bh=JkvoL6pP8QyU1QX5piOW3IBrL/iDOlfL3MYsYLrtraY=;
	b=a5F72wqIXVhQTyZUYg5Vl+pjB7xKhbRd78RB2KvCvujbHHR1QD8DoSnhc01ln/xKgg
	gMNO4R8FQuab6Le3zzXlYPQqheJb3uPr7j6P6j47Q69zdVxPnh08vCrtph+JADubBiXy
	bDgFdrPvgefgXGYB7Wc01nCvghJKnnAa1X6PWTP4BF+aJDenQDFL+/2FomCBLIzBiHv/
	9p4uBo9rbbj6yTnxcpz3BJNZPcY8kFMkajulLm7L2Es/JZtRlEkab+c0h94Pi30DPPiC
	O3iKxT86LGVXQ+TlAfytyIKAzb6aRQ05gQjMBnaODs9zM0eJtGBILAAAdjMay80C8H5m	DXSQ==
authentication-results: spf=pass (sender IP is 209.85.219.181)
	smtp.mailfrom=gmail.com; mit.edu; dkim=pass (signature was verified)
	header.d=gmail.com; mit.edu;	dmarc=pass action=none header.from=gmail.com; 
errors-to: piclist-bounces@mit.edu
list-id: "Microcontroller discussion list - Public." <piclist.mit.edu>
list-post: <mailto:piclist@mit.edu>
x-beenthere: piclist@mit.edu
x-mailman-version: 2.1.6
x-received: by 2002:a25:4608:: with SMTP id
 t8mr23041903yba.497.1607457529069; 	Tue, 08 Dec 2020 11:58:49 -0800 (PST)
x-topics: [EE]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

Hi Neil,

I had similar problems, when I was running a DSP->Gate Driver->BLDC Motor
powered from a Flyback SMPS.

https://e2e.ti.com/support/tools/sim-hw-system-design/f/234/p/819727/303469=
9#3034699

The DSP would RESET in between. Initially I was able to filter out the nois=
e
with a Common Mode Filter for the DSP stage.
You can see the DIY common mode filter, wound on a toroid in here

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-fi=
les/234/20190713_5F00_162901.jpg

Eventually, the problem was figured out that the BLDC motor was
generating the spikes,
which was getting looped in everywhere, DSP, Gate drivers, all places.

The pulses were from the BLDC motor, which I was able to clamp with diodes,
but still there was some mains noise.

Changing the Y capacitor between the Primary and Secondaries did help
for that specific problem.

SMPS's are a pain, if they are not designed correctly. If you are
driving large loads,
then the pain is also larger.

Chinese SMPS's dont even mention. Likely they have no filters!

Best Regards,
Manu


On Wed, Dec 9, 2020 at 1:13 AM Neil <picdude3@narwani.org> wrote:
>
> Looking at how common mode chokes work.  Was not aware of these.
>
> This is the power supply I'm using (not sure if it's a flyback), and I
> do not have any other caps...
> https://www.meanwell.com/Upload/PDF/MPM-10/MPM-10-SPEC.PDF
>
> Cheers,
> -Neil.
>
>
>
> On 12/8/2020 1:19 PM, Manu Abraham wrote:
> > I guess you need a common mode filter at the PSU 120V in might help.
> >
> > Other than that:
> > Are you using a flyback PSU ?
> > If so, do you have a High voltage capacitor (the one between the
> > primary and secondary, for the noise return path) ?
> >
> > On Tue, Dec 8, 2020 at 11:35 PM Neil <picdude3@narwani.org> wrote:
> >> Hi,
> >>
> >> I'm working on a device that takes 120VAC, converts to 5VDC with a
> >> PCB-mounted power supply, then further reduces that to 3.3VDC with a
> >> linear regulator.
> >> A 3.3V microcontroller switches a relay to power a 120VAC pump.
> >> Overview...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-00.jpg
> >>
> >> All has been great until we switched to a specific pump, which happens
> >> to generate a LOT of conducted noise, which passes through the 5V PS,
> >> and the 3.3V regulator, and causing the microcontroller to crash.
> >> I did a bunch of tested and found that the noise is being conducted
> >> through the wires back to the board through the PS, through the linear
> >> regulator, and this is the 3.3V line...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-01.jpg
> >>
> >> I was over at someone else's place so did not have a lot of parts with
> >> me, but...
> >> Adding a bunch more 0.1uf bypass capacitors all over the board did not=
 help.
> >>
> >> Changing the power supply from an IRM-10-5 (industrial spec, 200mV
> >> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce the ra=
te
> >> of the crashing... but the ripple itself wasn't causing crashing.
> >>
> >> Adding (non-specific size) ferrites to the pump wires, and 120VAC inpu=
t
> >> wires did not help.
> >> I then tried to create a crude/uncalculated LC filter (which whatever
> >> components I had on hand (33uh inductor and 1000uf capacitor, should b=
e
> >> low ESR), then a Pi filter (added 680 uF capacitor), and those barely
> >> made a dent.
> >> Eventually I added another 0.1uf capacitor to the output side of the p=
i
> >> filter and that helped enough to prevent the microcontroller crashing.
> >> But there is still a lot of noise on the 3.3V line...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-02.jpg
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-03.jpg
> >>
> >> FWIW, this is where it ended up...
> >> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-04.jpg
> >>
> >> The noise is in the 7Mhz to 30Mhz range (prob even higher).
> >> I feel like smaller, low-ESR ceramic caps should help, but I doubt it
> >> will take out most of the noise.
> >> What is the right type of filter to eliminate this noise?
> >>
> >> Cheers,
> >> -Neil.
> >>
> >> --
> >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> >> View/change your membership options at
> >> http://mailman.mit.edu/mailman/listinfo/piclist
>
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.