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'[EE]: +12V and +5V in automoble'
2001\01\24@091351 by Richard Sloan

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+12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on them.

I have looked at switching regs but they seem to be not the best for
availability and require expensive inductors etc for use. I want to build a
very cost sensitive device and am looking for other suggestions.

Yes heat is an issue that needs to be addresses also as a 7805 was attempted
and man does it get HOT!

Thanks.
Richard.

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2001\01\24@095502 by Gordon Varney (personal)

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Richard,
   You have not stated your input voltage. I assume that if you have tried
a 7805 that you are referencing a low DC value.

National makes a simple switcher. Easy to implement, and there are several
companies that make the inductors as an off the shelf part. Cost effective
and very few components.

12 Vdc @ 2.5 A is 30W, there will not be a cheep solution. But there will be
a least costly solution.

Gordon Varney

> +12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on
them.
>
> I have looked at switching regs but they seem to be not the best for
> availability and require expensive inductors etc for use. I want to build
a
> very cost sensitive device and am looking for other suggestions.
>
> Yes heat is an issue that needs to be addresses also as a 7805 was
attempted
> and man does it get HOT!
>
> Thanks.
> Richard.

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2001\01\24@100331 by Alan B. Pearce

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> I have looked at switching regs but they seem to be not the best for
> availability and require expensive inductors etc for use. I want to build

I guess that should be "relatively expensive". I found that I could get largish
toroid inductors from Pulse for about GBP0.8 (a little over a $US1). If it was
going to save trying to dissipate 7W of heat in a hot environment I guess the
inductor is "relatively cheap".

Now it is a while since I looked at them and I do not recall if the specific
inductor I was looking at is suitable for a switching regulator, but at that
price I would have a pretty good try.

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2001\01\24@100536 by Richard Sloan

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Sorry input would be the 13.8V-14.4V car system.

-----Original Message-----
From: pic microcontroller discussion list
[spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU]On Behalf Of Gordon Varney (personal)
Sent: Wednesday, January 24, 2001 9:52 AM
To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
Subject: Re: [EE]: +12V and +5V in automoble


Richard,
   You have not stated your input voltage. I assume that if you have tried
a 7805 that you are referencing a low DC value.

National makes a simple switcher. Easy to implement, and there are several
companies that make the inductors as an off the shelf part. Cost effective
and very few components.

12 Vdc @ 2.5 A is 30W, there will not be a cheep solution. But there will be
a least costly solution.

Gordon Varney

> +12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on
them.
>
> I have looked at switching regs but they seem to be not the best for
> availability and require expensive inductors etc for use. I want to build
a
> very cost sensitive device and am looking for other suggestions.
>
> Yes heat is an issue that needs to be addresses also as a 7805 was
attempted
> and man does it get HOT!
>
> Thanks.
> Richard.

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2001\01\24@110013 by Gordon Varney (personal)

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> Sorry input would be the 13.8V-14.4V car system.
>
> > +12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on
> them.
> >

Richard,
   The 12 Vdc will be a small problem for you.  The output voltage is very
close to the input voltage. I doubt that a switcher is very practical for
this low of an input. I recommend an LDO like the LMS1585CSX-ADJ. A simple
switcher for the 13.8 Vdc to 5 Vdc will be reasonable and fairly small.
There will be very little heat less than 5W in the 13.8 Vdc to 12 Vdc. Also
consider how important it is to stay regulated at 12 Vdc. The battery of the
vehicle can drop below 12 Vdc at start up and in case of lights left on, the
battery may drop to 10 or 11 Vdc or lower. If you require 12 Vdc regulated
under these conditions consider a buck-boost regulator.

Gordon Varney

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2001\01\24@142017 by Charles Morgan

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For the 5V portion, see the June 98 issue of Nuts&Volts (or see
http://www.seetron.com/an_vpwr1.htm for a summary).  The supply uses a no-inductor
switching regulator and is rated at 1A.

Charles Morgan

>+12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on them.
>I have looked at switching regs but they seem to be not the best for
>availability and require expensive inductors etc for use. I want to build a
>very cost sensitive device and am looking for other suggestions.

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2001\01\24@143026 by David VanHorn

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At 11:20 AM 1/24/01 -0800, Charles Morgan wrote:
>For the 5V portion, see the June 98 issue of Nuts&Volts (or see
>http://www.seetron.com/an_vpwr1.htm for a summary).  The supply uses a no-inductor
>switching regulator and is rated at 1A.

That's not a no-inductor switcher, it's a linear.
7W/A dissipation from a 12V supply.

Ye canna' change the lars o-physics!

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2001\01\24@143225 by David VanHorn

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At 11:20 AM 1/24/01 -0800, Charles Morgan wrote:
>For the 5V portion, see the June 98 issue of Nuts&Volts (or see
>http://www.seetron.com/an_vpwr1.htm for a summary).  The supply uses a no-inductor
>switching regulator and is rated at 1A.

The second part they talk about is an integrated switcher.
The inductor is still there, but it's all encapsulated as a 'brick'
Be prepared for sticker-shock.

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2001\01\24@203920 by McMeikan, Andrew

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This is a multi-part message in MIME format.
--------------InterScan_NT_MIME_Boundary
Content-Type: text/plain

there are many different type of switching regs out there, the ones I used
were not all that fussy on inductors (did some by hand).

have a look at how I did it at http://opendesign.cx

       cya,    Andrew...

> {Original Message removed}

2001\01\25@043400 by Alan B. Pearce

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>-Adam
>(who keeps his baby as far away from his work bench as physically
>possible...)

So you are one of those people who work inside the playpen!

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'[EE]: +12V and +5V in automoble'
2001\02\05@013702 by Gennette, Bruce
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This problem will get *MUCH* worse real soon when the next generation of
cars goes to 42V (nominal 36V) batteries.

This move is to reduce the amps carried by the copper cable to reduce the
mass of the copper to allow the mass:engine power ratio to be increased a
little.  Oh, and it also improves the efficiency of the many small electric
motors in modern cars.

I'm sure some of the companies are already working on a single chip solution
to derive 3, 5, 12 & 24V from the 36V to power uC and legacy devices.

Bye.


> {Original Message removed}

2001\02\05@070256 by Russell McMahon

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> > +12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on
> > them.
> >
> > I have looked at switching regs but they seem to be not the best for
> > availability and require expensive inductors etc for use. I want to
build
> > a
> > very cost sensitive device and am looking for other suggestions.
> >
> > Yes heat is an issue that needs to be addresses also as a 7805 was
> > attempted
> > and man does it get HOT!


HOW cost sensitive.
Switching regulators are almost certainly the correct solution.
What power levels are you dealing with?
A modern switcher will run at a frequency of around 1 MHz (maybe more) and
will use surface mount inductors for modest power levels. When all costs are
considered (regulator, heat sink, wasted power from passive regulator,
incremental wiring and battery cost (trivial for a single application) etc
the switch reg is liable to be attractive. Not as easy to design though :-).


Russell McMahon

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2001\02\05@101640 by Thys Van Tonder

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Hi

The Simple Switcher From National works very well in this application. I
think Motorola also makes a similar device. You can get some off the shelf
inductors from Newport, or just get the cores from Siemens Matsushita (if
that is still the name) or "Neosid" (don't think this is how you spell it)
and wind them your self.

Regards
Thys

{Original Message removed}

2001\02\05@173528 by Chris Carr

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I agree with the sentiments of both Russell & Thys.

One point I have not seen mentioned is that to obtain +12 volts from an
automotive battery you have to use a switched mode regulator, more
specifically a buck boost convertor as you have to cater for the supply
voltage varying between 8 and 15 volts.

Whatever solution you use, ensure you have provide sufficient protection
against transients and inductive load dumps.

Regards
Chris

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2001\02\05@180031 by steve

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> The Simple Switcher From National works very well in this application. I
> think Motorola also makes a similar device. You can get some off the shelf
> inductors from Newport, or just get the cores from Siemens Matsushita (if
> that is still the name) or "Neosid" (don't think this is how you spell it)
> and wind them your self.

Nat Semi now have another range of similar devices (Son of Simple
Switcher ?) and online design tools. Go to the webpage, plug in the
values, select a part and do electrical and thermal simulation online.
You can also get it on cdrom.

For an automotive application many years ago, we built a pre-
regulator that bolted onto the car bodywork. It's a very good
heatsink if you want to stick with a linear reg.

Steve.


======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: stevebspamspam_OUTtla.co.nz      fax +64 9 820-1929
======================================================

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2001\02\06@175351 by Michael Rigby-Jones

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{Quote hidden}

I can see a whole new crop of problems appearing in the near future.  New
batteries will be extrememly expensive, and I suspect more fragile and open
to abuse form poor charging practices than current items.  Also what happens
when some helpfull person in a 42 volt car tries to give some poor soul with
a (12v) flat battery a jump start? Bang!

Oh well, the price of progress I guess.

Mike

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2001\02\06@181301 by Lance Allen

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Michael Rigby-Jones wrote:

> .... Also what happens
> when some helpfull person in a 42 volt car tries to give some poor soul with
> a (12v) flat battery a jump start? Bang!
>
> Oh well, the price of progress I guess.
>
> Mike
>

Do you think you will be allowed access under youre own cars bonnet (hood for
some of us in foreign lands)?
I mean to say... what possible business could you have under there, you might
hurt youre self or something..... just leave it all to the people in charge,
trust us, we know whats best for you.

Lance Allen
Embedded Systems Lab
CSE
Electronic and Electrical Engineering
School of Engineering
University of Auckland

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2001\02\07@011340 by Ray Russell

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In a message dated 2/6/01 5:56:49 PM Eastern Standard Time,
spamBeGonemrjonesspamBeGonespamNORTELNETWORKS.COM writes:


{Quote hidden}

Please remember this the next time you look at you mechanics bill! We are
averaging 75 completely new models a year now! My current database in my shop
now contains more then 26,000 megs of data! this only represents cars and
light trucks made from 1984 to date. The subscription just to keep this thing
up to date costs us $200 a month. Never mind the new tools we buy weekly just
trying to keep pace!

Ray Russell
General Contractor
Norfolk & Western Railroad

Pocahontas Division
Circa 1958
Visit The Pocahontas Website at:
<A HREF="http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm">Click here: Pocahontas Home</A>
OR
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm

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2001\02\07@072021 by Michael Rigby-Jones

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{Quote hidden}

Well, to be honest, I've never had a mechanics bill.  I have always
serviced/repaired my own cars, including engine rebuilds, body repairs,
electrics etc.

Mike

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2001\02\07@093349 by M. Adam Davis

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I imagine that they have already thought of this.  Chances are it will
have some completely different interface (ie, nothing to get a pair of
cables onto).

It would be clearly marked, and you'd probably have to buy special 42v
only cables.

But chances are they'd overcome the problem completely by either never
letting the battery go too low to start the vehicle, or have a spare
starting battery which has to be manually switched into the system (or
switched by the processor?  Hmmm...)

Otherwise you have the dangers of exploding 12v batteries - something
insurance companies would sue car companies for.

And, of course, you'd get a crop of jumper cables which have high-current
DC-DC converters on them.

-Adam

Ray Russell wrote:
{Quote hidden}

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2001\02\07@104030 by David VanHorn

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At 09:34 AM 2/7/01 -0500, M. Adam Davis wrote:
>I imagine that they have already thought of this.  Chances are it will
>have some completely different interface (ie, nothing to get a pair of
>cables onto).
>
>It would be clearly marked, and you'd probably have to buy special 42v
>only cables.

Actually, I'd love to have 300A powerpoles on jumper cables.
No more wrong hookups, no connecting to the wrong place.
I don't have a problem doing it right with gator clips, but I know many
people do.

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2001\02\09@172918 by Charles Morgan

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Richard, I noticed that BG Micro is selling a 12V, 3A automotive power
supply that was originally meant to power a briefcase printer.  Catalog
says it's fused and regulated and has a cigarette lighter plug.  Cost is
$4.95, part no. PWR1089.

Charles Morgan


At 09:13 AM 1/24/01 -0500, Richard Sloan wrote:
>+12V @ 2.5A and +5V @ 1A, what is the best solution can have +/-10% on them.
>
>I have looked at switching regs but they seem to be not the best for
>availability and require expensive inductors etc for use. I want to build a
>very cost sensitive device and am looking for other suggestions.

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