From: Sean Breheny <shb7@cornell.edu>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Sun, 19 Jan 2020 15:40:44 -0800
Subject: Re: [EE] Magnetic lock
Thread-Topic: [EE] Magnetic lock
Thread-Index: AdXPI302AmVMGYY7Rpyib+jBJT+WGg==
Message-ID:
 <CAE8uMMqYV6CTD8LtJPLz_KRR-jnfGjoaieQ_RRQOW0RiHk728g@mail.gmail.com>
References:
 <CAE8uMMp3OOrWLdj_nK0Z1ctP2k1x1aLL1rWC6vNQe0V=JwdbUw@mail.gmail.com>
	<CAFo_nNr_-Ou-z290+=48x4S091=R_ZWpWbzdwJigSh07NAuOog@mail.gmail.com>
	<CAE8uMMrYmTnZpr-dxU0hjSdPO5NxRGMHcA=N-h_OrB3RLgMkNw@mail.gmail.com>
	<DA776B01-DB4F-406C-9359-D5422C6ACB75@gmail.com>
In-Reply-To: <DA776B01-DB4F-406C-9359-D5422C6ACB75@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
	209.85.208.48 as permitted sender) receiver=protection.outlook.com;
	client-ip=209.85.208.48; helo=mail-ed1-f48.google.com;
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed;	d=cornell.edu;
 s=g.20171207;
	h=mime-version:references:in-reply-to:from:date:message-id:subject:to;
 	bh=DEXTTNBD1Q4gMafGNtmSggKzCrGTo379zxiPoj7slbg=;
	b=nSEYzw0uIDF2UJAQjnZfWOqtCuKy/5zEL3mXZQURYCPhWXC5+NkHLC55pGpdFKhVmt
	Ik7MGwGRZPE2f9sHGpK1GJbbuVK9kufvvrWpUCTuj3Y9X+1OYUFtxtMeE/PhkDUK+I/9
	JoH3CjmryiX7XPuhXj9/6nBUmSZ3tKX0Cx10BRKqCaHR4U9I2nlF6hE+2QQM67256W4c
	caGvgfCQcd1BWOwbtcvhM2b+OvAYcgi3GN4TLhUiEF5ITS7vST/5Q+weqHPHLVv7/vdk
	//E0P5O3DueiAWGCVbQrI4PM1sQr0h2+IR4QBltcGn2AtnpFFyd4anaSehWIMSZl6p+D	aAsQ==
authentication-results: spf=pass (sender IP is 209.85.208.48)
	smtp.mailfrom=gmail.com; mit.edu; dkim=pass (signature was verified)
	header.d=cornell.edu;mit.edu; dmarc=pass action=none
	header.from=cornell.edu;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:a17:906:23e2:: with SMTP id
	j2mr17872722ejg.257.1579477256785; 	Sun, 19 Jan 2020 15:40:56 -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

Not necessarily - AC solenoids have 120Hz force ripple because as I said
the force peaks twice per cycle (it would be different if there were a
permanent magnet involved where you could have repulsion).

On Sun, Jan 19, 2020, 6:26 PM Dr Skip <drskip@gmail.com wrote:

> 120Hz buzz, wouldn't that imply full wave rectified DC?
>
> -Dr Skip
>
>
>
> On January 19, 2020 3:58:00 PM EST, Sean Breheny <shb7@cornell.edu> wrote=
:
> >I definitely have seen some that are AC (they have an audible 120Hz
> >buzz -
> >120Hz because they attract more strongly on both positive and negative
> >peaks)
> >
> >On Sun, Jan 19, 2020 at 12:36 PM David C Brown <dcb.home@gmail.com>
> >wrote:
> >
> >> They are DC
> >> __________________________________________
> >> David C Brown
> >> 43 Bings Road
> >> Whaley Bridge
> >> High Peak                           Phone: 01663 733236
> >> Derbyshire                eMail: dcb.home@gmail.com
> >> SK23 7ND          web: www.bings-knowle.co.uk/dcb
> >> <http://www.jb.man.ac.uk/~dcb>
> >>
> >>
> >>
> >> *Sent from my etch-a-sketch*
> >>
> >>
> >> On Sun, 19 Jan 2020 at 16:25, Sean Breheny <shb7@cornell.edu> wrote:
> >>
> >> > If the electromagnet uses AC then it will indeed draw less current
> >when
> >> it
> >> > is closed against the piece of metal it attracts. This is because
> >there
> >> is
> >> > no longer an air gap in the magnetic circuit so the inductance is
> >higher.
> >> >
> >> > On Sat, Jan 18, 2020, 8:43 PM mike brown <mike@n5qmg.com wrote:
> >> >
> >> > > In my experience, the electromagnet appears to draw less current
> >when
> >> > > latched to the metal plate.  This is an unscientific observation
> >based
> >> > upon
> >> > > the temperature of the magnet increasing when not latched to the
> >steel
> >> > > plate.  Amazing that they can generate such a strong holding
> >force
> >> using
> >> > > three watts of power as long as the two parts perfectly mate to
> >each
> >> > other.
> >> > >
> >> > > On Sat, Jan 18, 2020, 19:07 Bob Blick <bobblick@outlook.com>
> >wrote:
> >> > >
> >> > > > Admin message to Allen, since his email address seems to reject
> >> direct
> >> > > > email.
> >> > > >
> >> > > > Hi Allen,
> >> > > > Please, when you reply to a piclist post, insure that the
> >subject
> >> line
> >> > > > topic tag is not preceded by your own email system's bracketing
> >> system,
> >> > > > because it does not conform to the piclist topic tag
> >definitions and
> >> > > > interferes with our archiving system, and also with users that
> >rely
> >> on
> >> > > the
> >> > > > topic tag to sort their piclist emails.
> >> > > > Thanks.
> >> > > > Bob
> >> > > >
> >> > > > --
> >> > > > 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
> --
> 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
.