From: Dr Skip <drskip@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Sun, 19 Jan 2020 15:23:20 -0800
Subject: Re: [EE] Magnetic lock
Thread-Topic: [EE] Magnetic lock
Thread-Index: AdXPIRulvYfgtKCdRY67VguwOKbUyQ==
Message-ID: <DA776B01-DB4F-406C-9359-D5422C6ACB75@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>
In-Reply-To:
 <CAE8uMMrYmTnZpr-dxU0hjSdPO5NxRGMHcA=N-h_OrB3RLgMkNw@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
	209.85.161.48 as permitted sender) receiver=protection.outlook.com;
	client-ip=209.85.161.48; helo=mail-yw1-f48.google.com;
dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com;
 s=20161025;	h=date:disposition-notification-to:return-receipt-to:in-reply-to
	:references:mime-version:content-transfer-encoding:subject:to:from
	:message-id; bh=C5Ndgegu5YozI6rfA/EVOx1CliANp3PLKjiRKEy62MI=;
	b=HvlGIC5IxsOXlarncAcvw0svh0G43mxK6XFzpx9gVxN8idVjWNXQSUiYcujKAKmxSv
	rfwxuB2iSs6iXtvgcX2fv0ZUcIudeXMj5ig1jYyw8eClWvxCo3YZmP+SyQbkuYzcHLMd
	sZSsHzUchqZNoDmJ5aJzmoHhorYzQ+yA0FCb+RPU0MWkdiFEpkLtGLTQ049JcmKSHdWF
	J8auUkMgvXcc72zxD3Kt2xw9/z2ssBTwbbsX9LIAA3OOuG5jlv/W7YkMnCtpvrITwFKy
	Ug93Zpzo5yhv+s3IMO/wdC2PgLt9Qd6qYjkbd1DDmcIHEXEkNKRHFBE7uGVoRnTn/Kyf	X5YA==
authentication-results: spf=pass (sender IP is 209.85.161.48)
	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:a81:6d17:: with SMTP id
 i23mr11871530ywc.58.1579476206922; 	Sun, 19 Jan 2020 15:23:26 -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

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
>>
>--=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
--=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
.