From: Neil <picdude3@narwani.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Tue, 8 Dec 2020 11:13:32 -0800
Subject: Re: [EE] Eliminating external noise through PS
Thread-Topic: [EE] Eliminating external noise through PS
Thread-Index: AdbNl65VS98hNSPTQpiulTlqaTrXgg==
Message-ID: <5FCFD05C.2020408@narwani.org>
References: <5FCFC00E.8040703@narwani.org>
	<CAH-Cr=LPKqeVT5XJtMLCUNx2TBu38smpkkGkzUxWL3eF7OGU_g@mail.gmail.com>
In-Reply-To:
 <CAH-Cr=LPKqeVT5XJtMLCUNx2TBu38smpkkGkzUxWL3eF7OGU_g@mail.gmail.com>
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: None (protection.outlook.com: narwani.org does not designate
	permitted sender hosts)
dkim-signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
 d=narwani.org	; s=default;
	h=Content-Transfer-Encoding:Content-Type:In-Reply-To:
	MIME-Version:Date:Message-ID:Reply-To:From:To:References:Subject:Sender:Cc:
	Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender:
	Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:
	List-Subscribe:List-Post:List-Owner:List-Archive;
	bh=HaUfpZbPrjUEt4NNH3WEDnp12oQ/BHARJz9F7Hh4LmY=;
	b=1FQLWMXfoXr1eO64EsyfObHFuQ
	+tFqtlTTPS9DVX025oa0vstoqmznHIqWDXIxncc/RpqhG6HspHRPS9CDrzspwfEyY2AYZFxxav+E1
	fAZ1kS8K5lYt+uqjE0XjwMOSugj4kr4nONZKd6nff4YCzLju9OdyjPIoi66Ie1gaTAdmZ3D4Dqltd
	vHN11yQ1fidaBjfUVn2GTsvYJNQeZsZxVDN6/y6KkwruSQpzuAmfswozMeM7iHOZh2VK2Gn0rQVwK
	9nWIOySc5HwMQRTGSaWJ9TCVMxy3eoAm+nedjVtfNnACtXLXpgkLIJ31EH13pI0PLhtfFqTCT3m3i
	yGxKWIqg==;
authentication-results: spf=none (sender IP is 68.65.123.241)
	smtp.mailfrom=narwani.org; mit.edu; dkim=pass (signature was verified)
	header.d=narwani.org;mit.edu; dmarc=bestguesspass action=none
	header.from=narwani.org;
user-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101
	Thunderbird/38.5.0
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-source-args:
x-source-dir:
x-antiabuse: Sender Address Domain - narwani.org
x-source:
x-authenticated-sender: premium47.web-hosting.com: ca4@narwani.org
x-topics: [EE]
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

Roy,

Battery... ugh.  Outdoor application that's drawing over an amp currently.

In the given enclosure, the micro is on the other corner (quadrant) of=20
the board from the 120VAC.  Some things have changed, so I am able to=20
push it a bit further on the next revision but not much. Layout here...
http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-05.jpg
The lower left is 4 relays, fuses, and screw terminal blocks.

Not sure what you mean by Schotty diodes on 5V to + & -, as it's the=20
power rails that are going above spec.
I was thinking 5.1V zener on the 5V line, but the PS seems to have a=20
built in zener at the output.  And not sure how a zener without a series=20
resistor would handle the power.

Will look into a harmonic filter.

Thanks,
-Neil.



On 12/8/2020 1:18 PM, roy hopkins wrote:
> Run the micro on batteries?
> Take the micro further away from the motor power, power it from a differe=
nt
> phase?
> Schottkyy Diodes on 5v to + and - to limit voltage swings to 5v +/- 0.2
> volts.
> Harmonic filter?
>
>
> Roy Hopkins
> ZL1RJH
>
>
>
>
> On Wed, 9 Dec 2020 at 07:05, 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 rate
>> of the crashing... but the ripple itself wasn't causing crashing.
>>
>> Adding (non-specific size) ferrites to the pump wires, and 120VAC input
>> 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 be
>> 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 pi
>> 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
>>

--=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
.