From: Richard Prosser <rhprosser@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sender: "piclist-bounces@mit.edu" <piclist-bounces@mit.edu>
Date: Mon, 27 Apr 2020 14:22:18 -0700
Subject: Re: [EE] Voltage regulator with high input voltage
Thread-Topic: [EE] Voltage regulator with high input voltage
Thread-Index: AdYc24hnSMyCC55+Rwuo5KdrRa6Lqg==
Message-ID:
 <CAEBHKaevAW4_pk38Q_yfNF9ZArGACZSU2H+Z=z4isQaruQKsnQ@mail.gmail.com>
References:
 <CAFo_nNp2c_0B6MP+Nv9OJBwjbo5QokUdgM8xL4zgSZAeYSXbOw@mail.gmail.com>
	<74ba642e-b6f8-16b4-9049-764f93d487c1@gmail.com>
	<5EA72863.6010608@narwani.org>
	<ce9a80b1-1ad8-5f57-14e0-36ed60c59e19@gmail.com>
	<5EA735E6.1010409@narwani.org>
In-Reply-To: <5EA735E6.1010409@narwani.org>
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
	209.85.210.41 as permitted sender) receiver=protection.outlook.com;
	client-ip=209.85.210.41; helo=mail-ot1-f41.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;
 	bh=qKrJ55ckUwy27hQOe/PDSesnvTlqw5eS63f7FCzysZE=;
	b=RofVoOqa2gw47rnW8HyP0kriFoRR8UJYI7ELnLS6/aH1Vqekmcrtp1crxIsBr7h/EB
	LCXuJt0N/DDeCCwxy39ZbtMEkV4vPawVhwod/J/YAHdbCpOo4N0NN2+RefAKseJwRGL0
	T+jq9ccABkfFMyVdJHt1Hm9dXtot8Eh5JVj2jKUZiOy6bD4ON88lC1fHd2/F5InRAfe2
	jOoxx3VRXe+8K5D+L1OWIfI0zw0EUfbvpqkxuEmb8RvtoepiDo3o5po+tIw1Ble3Vb0L
	wikotk1Kf5Y0AAf1aPboTg0CU4iwk/AShLPIriEtvG8ZT027kqf7ULKE0puekS53aVmo	UsAg==
authentication-results: spf=pass (sender IP is 209.85.210.41)
	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:aca:4f09:: with SMTP id d9mr596485oib.172.1588022547406;
	Mon, 27 Apr 2020 14:22:27 -0700 (PDT)
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

One solution I've used for this sort of thing is to modify a switchmode
wall-wart. You can often modify them by changing a couple of resistors to
work on a lower input voltage. Not sure if you'd get down to 36V but you
might. If you start with a 110V version you'd have a better chance. Adding
a few turns to the transformer internal power winding can assist also.
RP

On Tue, 28 Apr 2020 at 07:45, Neil <picdude3@narwani.org> wrote:

> Gotcha.
>
> One more question -- does the 270-ohm resistor need to be that low. If
> he's dropping from 40V to 8.2V, that resistor will need to be high
> wattage.  Shouldn't a much higher value work here?
>
> Cheers,
> -Neil.
>
>
>
> On 4/27/2020 3:08 PM, Isaac Marino Bavaresco wrote:
> > Neil,
> >
> > V+ is an output to other circuits that use unregulated voltage.
> >
> > Cheers,
> >
> > Isaac
> >
> >
> >
> >
> > Em 27/04/2020 15:45, Neil escreveu:
> >> Isaac,
> >>
> >> What's the purpose of V+ in this?
> >>
> >> Cheers,
> >> -Neil.
> >>
> >>
> >>
> >> On 4/27/2020 2:36 PM, Isaac Marino Bavaresco wrote:
> >>> Something like the image below.
> >>>
> >>> Change the Transistor, Zener, capacitor and resistor to your needs.
> >>>
> >>> Cheers,
> >>>
> >>> Isaac
> >>>
> >>>
> >>>
> >>> Em 27/04/2020 14:24, David C Brown escreveu:
> >>>> I am designing a current monitor for my e-bike.  Using an INA169 hi
> side
> >>>> current senor into a mid range PIC with a two digit LED display.
> >>>>
> >>>> Problem is getting the 5 volts for the PIC from the e bike battery
> which is
> >>>> nominally 36v but can rise to over 40 volts when fully charged.  Mos=
t
> small
> >>>> linear regulators seem to be rated at 36v..
> >>>>
> >>>> Current would be a couple of milliamps with the display off (most of
> the
> >>>> time).  Nearer 100 with the display on..
> >>>>
> >>>> Any suggestions
> >>>>
> >>>>
> >>>> __________________________________________
> >>>> 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*
> >>>
>
> --
> 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
.