From: Neil <picdude3@narwani.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Wed, 30 Dec 2020 16:25:55 -0800
Subject: Re: [EE] Eliminating external noise through PS
Thread-Topic: [EE] Eliminating external noise through PS
Thread-Index: AdbfDKCOKpfb7SUrR9WeUCNVCseUFA==
Message-ID: <5FED1A93.6050502@narwani.org>
References: <5FCFC00E.8040703@narwani.org>
	<004f01d6cf54$9da13a80$d8e3af80$@functech.com>
	<5FD3D1E9.8040605@narwani.org>
	<CAOFvGD6p9ft6iymUzaeSP99jmLVOHxXQbBHLHyP6FDck+n7TvA@mail.gmail.com>
	<5FD6A0DC.4010801@narwani.org>
	<CAOFvGD40+Nk9Ei_L1GmUp9DPWaOpFDD1940EFG4gy21ovaKk=Q@mail.gmail.com>
	<5FD6AEAF.6090505@narwani.org> <5FEB7356.7020408@narwani.org>
	<CAB115wF8W1HyYyMSHpG-E-Axv5AyOvVZi=r7_C5yVmYrRcAaiQ@mail.gmail.com>
In-Reply-To:
 <CAB115wF8W1HyYyMSHpG-E-Axv5AyOvVZi=r7_C5yVmYrRcAaiQ@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:From:Reply-To: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=MDbFMl7h1oS0EKs2AfsFbqsvEJL9RgCOUcD2PMLQ2P4=;
	b=jv8SbfXZ2lMSCBB5eW9k7Fha9X
	+TiZz0UvI7WDYrsToKqHmP6UnNOIho8xdxWSXDpWcauXm7I6TwMoD/RoahKJ7EM+tPRgoPGbxPjc6
	CSgD0SVREWtWvqxMCCgS1uqf/xvm4mWkf3djoE6hF/HojgU6FOZeMgJjsIPTFhOqHT8bXbCceLDeG
	prAEinlHzijM+x+GUEbnKSc32MH5aLt7gbIu6e/YFIlqnyIa0fnVwM4RsJVvUA8dsZwvbxSprR7B4
	AIa5xLFk0CS2KK4TYls57wzJBSp2seRxBsCuEQ6M60t0l1GVikn/4R3nhi7W5Z8jYLYsmIlJ4GHrI
	EQzJormg==;
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

Interesting thought... 10k pullup to +3v3.




On 12/29/2020 5:13 PM, David VanHorn wrote:
> What's your reset circuit look like?   High enough impedances here can
> cause these problems.
>
> On Tue, Dec 29, 2020, 11:22 AM Neil <picdude3@narwani.org> wrote:
>
>> Happy holidays everyone.
>>
>> Okay, I got back to this recently and have a bunch of updates:
>>
>> For the tl;dr 'ers... I've got a lot of noise out, the processor does
>> not crash anymore, but 2 questions remain:
>>
>> - Should I have the AC-outlet ground wire, coming onto the PCB and used
>> as a shield?
>>
>> - If I hold the AC wire with my hand, the noise (as seen on the
>> oscilloscope) drops (noticeably).  Shielding the AC wire does not have
>> the same effect, so what is happening here, and how can I use this to
>> help reduce the noise even more?
>>
>>
>> For the gory details, here's my summary of what I tried and found...
>>
>> For reference...
>> http://orlandorobotbuilders.com/stuff/SMNoise/20201224-SMN-08.jpg , and
>> noise is mostly in the few Mhz range and higher.
>>
>> - Ceramic cap across (DC) motor wires (right at the motor) helped a bit.
>> - Low-pass filter helped minimally
>> - Pi filter was a bit better, but still small impact.
>> - Common mode choke (uncalculated, but should've been able to separate
>> 60Hz from Mhz-range noise) didn't help.  I am new to these, but
>> apparently above some frequency the impedance drops again.
>> - Ferrite across AC side of motor wires helped minimally.
>> - Ferrite on incoming-power AC wires did not help
>> - Removed relay (and jumper across contacts to run the pump) to see if
>> noise was coming into board from that side, but nope.
>> - Started from scratch with a minimal setup -- the AC-DC PS (no PCB),
>> with wires soldered on for the incoming power and parallel wires to run
>> the pump, and a 1k load resistor on the PS output. Still a lot of noise
>> - Low-pass filter again helped reduce noise minimally.
>> - Capacitance multiplier helped noticeably.
>> - 2 more ceramic caps from each motor wire to ground/motor case (right
>> at the motor) helped noticeably.
>> - Twisted the AC wires to the motor tighter, and didn't really see any
>> difference.
>> - Back to original board, to use some of these, but too much voltage
>> drop on capacitance multiplier to be usable.  I should calculate this
>> properly and find the right transistor for this.
>>
>> At this point, I have 3 @ 0.01uf ceramic caps at the motor and the pi
>> filter and the board isn't crashing, but I can still see some noise on
>> the scope, which I'd like to reduce even more.  Going to try a
>> multi-stage pi/LC filter.
>>
>> But I'm curious how to use the "phenomenon" where holding the AC wire in
>> my hand reduces noise noticeably, to help this.
>>
>>
>> Thanks,
>> -Neil.
>>
>>
>>
>> On 12/13/2020 7:15 PM, Neil wrote:
>>> That's a definite possibility at this point.  The original circuit
>>> (prior version) worked great with 2 layers, but I needed 2oz copper to
>>> handle the pump current.
>>> Never version works just as great.  Or  I should say "worked", until
>>> they decided to switch from the AC pump to this DC pump.
>>>
>>> Cheers,
>>> -Neil
>>>
>>>
>>>
>>> On 12/13/2020 6:58 PM, Jason White wrote:
>>>> Neil, from the pictures it looks like you're using a 2 layer PCB. Have
>> you
>>>> considered a 4 layer PCB? A continuous dedicated ground plane layer
>> would
>>>> drastically reduce the loop area (and thus susceptibility to EMI) of
>> your
>>>> traces.
>>>>
>>>> Otherwise, it may be worth considering moving the relays to a separate
>>>> board/area.
>>>>
>>>> On Sunday, December 13, 2020, Neil <picdude3@narwani.org> wrote:
>>>>
>>>>> I strongly feel so, because in my early tests, I:
>>>>> (a) disconnected one of the pump wires (so the pump wouldn't run), an=
d
>>>>> it was (expectedly) very clean (on the scope).
>>>>> (b) disconnected both of the pump wires and plugged it into the femal=
e
>>>>> side of a PC power cord, so the pump ran, but was connected to 120VAC
>>>>> from a different source.  Very clean power again.
>>>>> In both cases, all else stayed the same including where the wires wer=
e
>>>>> draped, etc.
>>>>>
>>>>> In other tests, I moved the scope, power lines, etc and no change to
>> the
>>>>> noise on the line.
>>>>>
>>>>> Either way, I haven't done my other tests yet since I took the pump
>> with
>>>>> me, so I'll get to those this week.
>>>>>
>>>>> Cheers,
>>>>> -Neil.
>>>>>
>>>>>
>>>>> On 12/11/2020 7:37 PM, Jason White wrote:
>>>>>> Hi Neil,
>>>>>>
>>>>>> This may be a silly question: are you sure that some of these voltag=
e
>>>>>> spikes that you've captured on the scope are not artifacts of your
>>>>>> measurement setup? The loop formed by the ground wire/clip on a scop=
e
>>>>> probe
>>>>>> makes a very effective antenna. Maybe your power rail is cleaner tha=
n
>> you
>>>>>> think - in which case the true problem might be elsewhere.
>>>>>>
>>>>>> -Jason White
>>>>>>
>>>>>> On Fri, Dec 11, 2020 at 3:11 PM Neil <picdude3@narwani.org> wrote:
>>>>>>
>>>>>>> Sorry, disappeared for a couple days, but some quick answers to
>>>>>>> everything for now, and my next steps:
>>>>>>>
>>>>>>> - Yes I have flyback diodes.   Highlighted with yellow here,  just
>> above
>>>>>>> the relays...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-06.jpg
>>>>>>> - James & Russell, in that diagram also, I labeled the paths for
>> power.
>>>>>>> The 5V to the relays is pretty much dedicated and 5V is on the top
>>>>>>> layer, and (dedicated) ground for the relays on the bottom layer.
>> But
>>>>>>> yes, it's right up against the AC section, but as many components
>> have
>>>>>>> been removed now, I will push that far away.
>>>>>>> - The 3.3V regulator has been getting a bit warmer than I like, so =
I
>>>>>>> have been planning to use a buck converter instead.  But maybe I
>> should
>>>>>>> run two 3.3V regulators instead?  I would think that the buck
>> converter
>>>>>>> would be pass less of the noise through.
>>>>>>> - I ran over there quickly to pick up stuff and tried a crude
>>>>>>> (uncalculated) common-mode choke I made up from stuff I could find.
>> Did
>>>>>>> not make in dent in the noise coming through.
>>>>>>> See here...
>>>>>>> http://orlandorobotbuilders.com/stuff/SMNoise/20201207-SMN-07.jpg
>>>>>>> - I feel like Brent may be correct, that the noise may be coming fr=
om
>>>>>>> the relay side.  The processor (ESP32) is resetting.  I know it's
>> not a
>>>>>>> firmware issue as it had zero crashes with the previous pump.
>>>>>>>
>>>>>>>
>>>>>>> Adding some info:
>>>>>>> The previous pump was a huge AC pump.  This new pump is actually DC=
,
>> but
>>>>>>> there's a bridge rectifier on the wires.  So I'm now convinced that
>> the
>>>>>>> noise is coming from brushes.
>>>>>>> I brought the pump with me, and I have a new blank board.  My plan
>> is to
>>>>>>> reproduce just enough of the circuit to see the noise, and I can cu=
t
>> and
>>>>>>> re-route traces (the 5V & ground to the relays) to see if helps.
>>>>>>> I will also add a ceramic capacitor to the pump wires (right at the
>>>>>>> pump), and hope that helps.  Plus twist the wires.
>>>>>>>
>>>>>>> I'll be back with some results.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Neil.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 12/10/2020 7:28 PM, FTL wrote:
>>>>>>>> This is almost too obvious, but in the schematic I do not see a
>> flyback
>>>>>>>> diode across the relay to suppress the back EMF when the relay is
>>>>> turned
>>>>>>>> off. The lack of diode would cause a serious spike in the 5V suppl=
y
>>>>> when
>>>>>>> the
>>>>>>>> relay is turned off.
>>>>>>>>
>>>>>>>> Is the transistor being turned on hard enough to keep the relay on
>>>>>>> properly.
>>>>>>>> If it is not fully on with no flyback diode, maybe it is
>> occasionally
>>>>>>>> releasing and causing big noise on the 5V bus.
>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> On Behalf
>> Of
>>>>>>> Neil
>>>>>>>>> Sent: December 8, 2020 11:04 AM
>>>>>>>>> To: Microcontroller discussion list - Public. <piclist@mit.edu>
>>>>>>>>> Subject: [EE] Eliminating external noise through PS
>>>>>>>>>
>>>>>>>>> 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 conduct=
ed
>>>>>>>> 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 di=
d
>> not
>>>>>>>> help.
>>>>>>>>> Changing the power supply from an IRM-10-5 (industrial spec, 200m=
V
>>>>>>>>> ripple) to MPM-10-5 (medical spec, 100mV ripple), helped reduce t=
he
>>>>> 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 doub=
t
>> 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
>>>>>>>
>>>>> --
>>>>> 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
>>

--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.