From: RussellMc <apptechnz@gmail.com>
To: Jason White <whitewaterssoftwareinfo@gmail.com>
CC: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Fri, 24 Jan 2020 21:47:12 -0800
Subject: Re: [EE] H-Bridge supply voltage spike only in "reverse" (not
 forward)
Thread-Topic: [EE] H-Bridge supply voltage spike only in "reverse" (not
 forward)
Thread-Index: AdXTRduGto0HRuJhRu+Bz5T+OKqz3g==
Message-ID:
 <CACZQxzPZtxAyyofgokSDiv=BUJW6+cDy9ESGYcZtq_fNcNsYRQ@mail.gmail.com>
References:
 <CAOFvGD7LH=1TLBj58wAio2brw_348=ZPn3-rYjDHxE8KtsisVQ@mail.gmail.com>
	<CACZQxzMiedf1X1v=TM9BaKDfqJOkfYQke4Nnnzb3160r_kF9dg@mail.gmail.com>
	<CAOFvGD7SGQ0PtdRak2FmENoudzTy8mYGdYsorz0YGQGF5ayqBg@mail.gmail.com>
In-Reply-To:
 <CAOFvGD7SGQ0PtdRak2FmENoudzTy8mYGdYsorz0YGQGF5ayqBg@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: Pass (protection.outlook.com: domain of gmail.com designates
	209.85.208.46 as permitted sender) receiver=protection.outlook.com;
	client-ip=209.85.208.46; helo=mail-ed1-f46.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	:cc;
 bh=3/ERqVtTUaQY5fHPvQX6Mukqr5rPX2+c0aAlO+hjHso=;
	b=sGQCi+fZE18rLxjdGHZPCYYkx8XakG3B4lxl7Tb7JchfVH9U8g+1LrSQ+1yRituUnW
	aMJGcOWfMc9292N+aAXAfaHGNkMVgeryjbp++z7utpVdxE5HLIP3C5vGJKMBGqQua2j/
	CXoWQ6z/pRQxPJa1rGgUfFHS+L7ahr2bzBFi7aS1UCRKQ04RLkIexsWvIFNrNU2xHCJL
	qwu8MYFTuvIT9ZeWZvIcFaGpGoZsxoWd4OiJPMHFSNhBEwv9nFqDBjjsxnbmXILkRCeV
	ZqMDKyHSvdRspE76yswFrib4qlbQB+E1uuwNd5mhkiVwUAg1JEB+lEq2KxnvbP6KvhHn	Hs9Q==
authentication-results: spf=pass (sender IP is 209.85.208.46)
	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;compauth=pass reason=100
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:a05:6402:797:: with SMTP id
	d23mr5727655edy.138.1579931270514; 	Fri, 24 Jan 2020 21:47:50 -0800 (PST)
x-topics: [EE]
x-content-filtered-by: Mailman/MimeDel 2.1.6
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0

On Sat, 25 Jan 2020 at 04:42, Jason White <whitewaterssoftwareinfo@gmail.co=
m>
wrote:

> The pwm alternates between "forward"/"backwards" and "braking". The lower
> two fets are supposed to be conducting during the off period.
>
> Both conducting =3D braking.

Is it correct to assume that the lower two fets being on should prevent
> dumping into the supply rail?
>

It's an excellent assumption.
Reality suggests that it's not happening for some reason, if that's when
you get 'pump up'

 Also of note is the ground Of the waveforms is the bottom side of the
bridge shunt resistor.

If braking / recirculating current flows in the shunt it will affect the
reading BUT the magnitude is presumably small.


     Russell
--=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
.