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'BUCK REGULATOR'
1998\12\15@114630 by WIL REEDER

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face
Hi

I am working on a low power LCD video monitor for my weekend getaway. Solar
and wind power into 12v batteries. I would like to run this 6 volt LCD
monitor off 12v and avoid the losses of a linear regulator or the inverter
and wall wart. Lm2576A comes to mind but are not available onesies in this
town. I need about 5 watts.
Has anyone made a switchmode regulator with a c/f84 or a c508?? I probably
could use a few of these around the claim and an adjustable model would be
a hot item.
Any Ideas?
Thanks

Wil Reeder
spam_OUTteachtechTakeThisOuTspambc.sympatico.ca
Vancouver,Canada

1998\12\15@120308 by dave vanhorn

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>I am working on a low power LCD video monitor for my weekend getaway. Solar
>and wind power into 12v batteries. I would like to run this 6 volt LCD
>monitor off 12v and avoid the losses of a linear regulator or the inverter
>and wall wart. Lm2576A comes to mind but are not available onesies in this
>town. I need about 5 watts.
>Has anyone made a switchmode regulator with a c/f84 or a c508?? I probably
>could use a few of these around the claim and an adjustable model would be
>a hot item.
>Any Ideas?

Go to National Semiconductor's website and request a sample, or order from
DigiKey?
Making a processor based regulator is somewhere between a stunt, and a bad
idea.
It will be more complicated than doing it with the proper regulator chip.


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1998\12\15@120706 by evan

picon face
You could consider the Power Trends PT5101: 7-38 V in, 5 V out, max 1 A out,
85% eff, ~$20 (CDN!) from Digikey, onesies no problem.

(I'm in Surrey, BC, and use Digikey all the time, it's as easy as it gets.)

-Ed V.
Agile Controls

> {Original Message removed}

1998\12\15@121536 by keithh

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face
WIL REEDER wrote:
>
> I would like to ... avoid the losses of a linear regulator
> or the inverter
> Lm2576A comes to mind but are not available onesies in this

I recommend Micrel parts.
They compete by making improved versions of popular SMPSU chips,
for those wanting that little extra.

1998\12\17@000922 by Tjaart van der Walt

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face
WIL REEDER wrote:
>
> Hi
>
> I am working on a low power LCD video monitor for my weekend getaway. Solar
> and wind power into 12v batteries. I would like to run this 6 volt LCD
> monitor off 12v and avoid the losses of a linear regulator or the inverter
> and wall wart. Lm2576A comes to mind but are not available onesies in this
> town. I need about 5 watts.
> Has anyone made a switchmode regulator with a c/f84 or a c508?? I probably
> could use a few of these around the claim and an adjustable model would be
> a hot item.
> Any Ideas?
> Thanks

I also have a similar question for the SMPS guru's. I've
been asked to re-think a design where a PIC get its power
from a 100V-150V DC line. How the hell does one drop
around 90V DC without creating an oven? I don't want to
use light bulbs as it is a potentially dangerous device.

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1998\12\17@065943 by D. Schouten

picon face
Hi,

>I also have a similar question for the SMPS guru's. I've
>been asked to re-think a design where a PIC get its power
>from a 100V-150V DC line. How the hell does one drop
>around 90V DC without creating an oven? I don't want to
>use light bulbs as it is a potentially dangerous device.

Shouldn't be a big problem nowadays. There are lot's of
nice switching devices available today which are quite
easy to implement. Take a look at the Power Integrations
website at : http://www.powerint.com
They have the three terminal TOPswitch devices and offer
very good design support for starters.

Also SGS Thomson have just released some minimum component
count small SMPS IC's. Check out http://www.st.com

What you need is a buck or flyback step down converter
depending on wheter you need isolation or not.

Bye,

Daniel...

1998\12\17@090803 by Reginald Neale

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face
Tjaart asked:
>
>I also have a similar question for the SMPS guru's. I've
>been asked to re-think a design where a PIC get its power
>from a 100V-150V DC line. How the hell does one drop
>around 90V DC without creating an oven? I don't want to
>use light bulbs as it is a potentially dangerous device.
>

Tjaart:

If you don't need isolation, there are several devices. The Harris HIP5600,
Maxim 610/11/12, Unitrode UCC1889, ATT2405. But the cheapest approach is an
"oven." A 10K 2W Metal Oxide resistor will give you 9.5mA at 5V from a 100V
source. Yes, it gets hot, but it's simple and cheap.

Reg Neale

1998\12\17@110636 by Peter L. Peres

picon face
On Thu, 17 Dec 1998, Tjaart van der Walt wrote:

> I also have a similar question for the SMPS guru's. I've
> been asked to re-think a design where a PIC get its power
> from a 100V-150V DC line. How the hell does one drop
> around 90V DC without creating an oven? I don't want to
> use light bulbs as it is a potentially dangerous device.

You can try to build a small self-oscillating SMPS with 2 transistors and
a small ferrite core (pot + pot). Insulation will be a problem, and RFI is
something to think about imho. For 150V input you can use medium power
high voltage transistors designed for video amplifier duty.

If you do net need galvanic separation, then the transformer can be
replaced by a simple coil, although at this voltage ratio it does not look
like a good idea to me, at the first sight.

hope this helps,

Peter

1998\12\17@114635 by Ryan Pogge

picon face
May I ask what this "buck regulator" is for?
by buck do you mean deer?
because I have been trying to figure out a way to
build a PIC? based system that uses some sort of
motion detector to trigger a camera... the purpose
being to attach it to a tree and it takes a picture
whenever a deer walks near it....
anyone have any bright Ideas? I was thinking that
one of the cheep motion detectors sold at radio shack
could be interfaced to a solenoid switch of some type
with the PIC ...to depress the camera button.
I just wondered if anyone could offer me some
insight as to what to do, because I dont know
where to start.

Thanks allot guys,
Ryan



{Quote hidden}

1998\12\17@123525 by D. Schouten

picon face
Hi,

>I also have a similar question for the SMPS guru's. I've
>been asked to re-think a design where a PIC get its power
>from a 100V-150V DC line. How the hell does one drop
>around 90V DC without creating an oven? I don't want to
>use light bulbs as it is a potentially dangerous device.

Shouldn't be a big problem nowadays. There are lot's of
nice switching devices available today which are quite
easy to implement. Take a look at the Power Integrations
website at : http://www.powerint.com
They have the three terminal TOPswitch devices and offer
very good design support for starters.

Also SGS Thomson have just released some minimum component
count small SMPS IC's. Check out http://www.st.com

What you need is a buck or flyback step down converter
depending on whether you need isolation or not.

Bye,

Daniel...

1998\12\17@160618 by Ryan Pogge

picon face
May I ask what this "buck regulator" is for?
by buck do you mean deer?
because I have been trying to figure out a way to
build a PIC? based system that uses some sort of
motion detector to trigger a camera... the purpose
being to attach it to a tree and it takes a picture
whenever a deer walks near it....
anyone have any bright Ideas? I was thinking that
one of the cheep motion detectors sold at radio shack
could be interfaced to a solenoid switch of some type
with the PIC ...to depress the camera button.
I just wondered if anyone could offer me some
insight as to what to do, because I dont know
where to start.

Thanks allot guys,
Ryan

1998\12\17@162536 by paulb

flavicon
face
Ryan Pogge wrote:

> May I ask what this "buck regulator" is for?  by buck do you mean
> deer?

 No, nearly everyone on this list wants it "cheep".

> I have been trying to figure out a way to build a PIC? based system
> that uses some sort of motion detector to trigger a camera... the
> purpose being to attach it to a tree and it takes a picture
> whenever a deer walks near it....

> anyone have any bright Ideas? I was thinking that one of the cheep

 See, you want it cheep too!

> motion detectors sold at radio shack could be interfaced to a solenoid
> switch of some type with the PIC ...to depress the camera button.

 I think one of the surface mount PICs *may* be the right shape to
depress the camera button, bit it'd be easier to just machine a piece of
acrylic.

 As for the interface, I think you want a pair of monostables, one to
turn the trigger pulse from the PIR detector into the right length (and
not too long) to activate the solenoid, and the other to inhibit another
pulse for a reasonable length of time; i.e., set the duration between
pictures assuming the deer/ buck is still in view of the PIC.

 You could use a dual monostable; I think most of us would use a 74HC14
as it's more common and cheaper.

 I think you should know that PIR detectors work better on people who
have lots of naked skin to radiate heat; than animals (such as deer)
which are well insulated and designed for the cold.
--
 Cheers,
       Paul B.

1998\12\17@173953 by Russell McMahon

picon face
This is a traditional smps or buck regulator application.
At around 90% efficiency you can easily get say 10 watts out on TO220
devices with smallish heatsinks - enough for most PIC applications.

Lots of circuits and ics around - see eg the nice people at Linear
Technology who have vast quantities of app notes etc on their web
site. (http://www.linear.com/apps)

At this voltage you will probably need an external pass element.
I personally would like to see an isolated design at this voltage
level or an exceptionally trustable crow-bar circuit on the output.

While regulators using cpu based controllers are achievable the black
magic involved has already been well done by the IC manufacturers -
if you're not designing thousands then a dedicated IC is a better
choice.


regards

           Russell McMahon

From: Tjaart van der Walt <.....tjaartKILLspamspam.....WASP.CO.ZA>

WIL REEDER wrote:
>
> Hi
>
> I am working on a low power LCD video monitor for my weekend
getaway. Solar
> and wind power into 12v batteries. I would like to run this 6 volt
LCD
> monitor off 12v and avoid the losses of a linear regulator or the
inverter
> and wall wart. Lm2576A comes to mind but are not available onesies
in this
> town. I need about 5 watts.
> Has anyone made a switchmode regulator with a c/f84 or a c508?? I
probably
> could use a few of these around the claim and an adjustable model
would be
> a hot item.
> Any Ideas?
> Thanks

I also have a similar question for the SMPS guru's. I've
been asked to re-think a design where a PIC get its power
from a 100V-150V DC line. How the hell does one drop
around 90V DC without creating an oven? I don't want to
use light bulbs as it is a potentially dangerous device.

1998\12\17@221828 by Ray Doerr

picon face
   You can buy the LM2576A from http://www.digikey.com in quantities of one.  You
will pay a premium in quantities of one.

   I am also very interested in making a switching regulator using a pic
12c508.  I was thinking of switching the DC input of 40Vdc at a frequency of
50Khz using a SCR.  Then by using a large filtering cap on the output.

{Original Message removed}

1998\12\18@062908 by Adriano De Minicis

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face
Ryan Pogge wrote:

> May I ask what this "buck regulator" is for?
> by buck do you mean deer?

No, it's the nickname of a specific type of switch-mode power supply.
There are three types:

1) buck (or bucking) = step down (Vout less that Vin)
2) boost = step up (Vout greater that Vin)
3) flyback = inverting (output polarity opposite to input)

Adriano

1998\12\18@084700 by Eisermann, Phil

flavicon
face
       >    I am also very interested in making a switching regulator
using a pic
       >12c508.  I was thinking of switching the DC input of 40Vdc at a
frequency of
       >50Khz using a SCR.  Then by using a large filtering cap on the
output.

       How do you propose to turn off the SCR? Once it's latched
       on, you can't turn it off (and if you're switching DC,
       you need an auxilliary circuit that can reverse the
       anode-cathode bias). It turns off when the current
       through it drops to zero/reverses direction. Or is there
       some significant technique involved that i'm not aware of?

       Having just experimented with this (except not even using
       a micro), i'll second the suggestion made by someone else:
       Unless you're going to sell many (hundred) thousands, buy
       a premade regulator chip.

       I wanted to do it for the learning experience. It seems there
       is always a project that would really benefit from a SMPS, or
       where it just makes the most sense. But for building your
       first one, it will pay off to build a working SMPS using a
       speciality IC. In fact, look at LTC's app notes, understand
       what is going on, and build one of their circuits. Getting it
       right the first time is hard enough. Once you've had some
       experience, you'll have a better appreciation for the
       complexities and subtleties involved. That will go a long way
       towards getting your own design up and running. There are
       some really good books out there to help you, as well.

1998\12\18@090606 by Eisermann, Phil

flavicon
face
       I wrote:

>  >       How do you propose to turn off the SCR? Once it's latched
>  >       on, you can't turn it off (and if you're switching DC,
>  >       you need an auxilliary circuit that can reverse the
>  >       anode-cathode bias). It turns off when the current
>  >       through it drops to zero/reverses direction. Or is there
>  >       some significant technique involved that i'm not aware of?
>
       [snip]

       perhaps a LC tank circuit? and switch the SCR at
       the resonant frequency? *snicker* why didn't i
       think of that before? it's called a SCR-resonant
       converter. Or something like that. sorry folks.
       It's been a mentally draining week.

       -Phil

1998\12\18@091432 by WIL REEDER

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face
----------
> From: Ray Doerr <EraseMErrdoerrspam_OUTspamTakeThisOuTHOME.COM>
> To: PICLISTspamspam_OUTMITVMA.MIT.EDU
> Subject: Re: BUCK REGULATOR
> Date: Thursday, December 17, 1998 7:12 PM
>
>     You can buy the LM2576A from http://www.digikey.com in quantities of one.
You
> will pay a premium in quantities of one.

snip

This is a three dollar and change part (CDN). The Nation dealer in this
town does not stock ANY switch mode regulators of this series(FAI). They
will order  a roll for me. Digikey would put this part in my hands for
about $16.00 CDN (P&H ETC.). I can do this with a Pic, 1 transistor & 1 fet
for less money. Any Ideas?


Wil Reeder
@spam@teachtechKILLspamspambc.sympatico.ca
Vancouver,Canada

1998\12\18@230523 by Donald L Burdette

picon face
Hi all.

I've been reading this thread, and wondering why nobody has discussed the
two major problems with using a PIC for voltage regulation, particularly
in an off-line regulator:

1.  Regulation is a linear phenomenon.  PIC's are digital.
2.  You need a regulated voltage to run the regulator.

Of course, the first problem can be overcome by adding a few op-amps or
comparators, but why go to all that trouble when several huge
semiconductor manufacturers have dedicated entire engineering teams to do
it for you?

The second problem can be overcome by generating a 'bootstrap" voltage,
which is usually a high value resistor and a zener diode from line to
ground.  Of course, if this can run your regulator, maybe it could just
run your circuit directly.

There is a good way to get a few milliamps of power from the mains with
no IC's at all (you can get up to 50 or so, but that's pushing it).  It
is essentially a high voltage cap in series with a zener between the
mains lines, plus a directional blocking diode and filter cap.  There was
a lot of discussion a few months ago about the correct design to use
(safety, and all that bunk).  Perhaps check the archive for October,
maybe September.

Good luck.


Don
KILLspamdlburdetteKILLspamspamjuno.com

1998\12\21@000314 by Tjaart van der Walt

flavicon
face
Russell McMahon wrote:
>
> This is a traditional smps or buck regulator application.
> At around 90% efficiency you can easily get say 10 watts out on TO220
> devices with smallish heatsinks - enough for most PIC applications.
>
> Lots of circuits and ics around - see eg the nice people at Linear
> Technology who have vast quantities of app notes etc on their web
> site. (http://www.linear.com/apps)
>
> At this voltage you will probably need an external pass element.
> I personally would like to see an isolated design at this voltage
> level or an exceptionally trustable crow-bar circuit on the output.
>
> While regulators using cpu based controllers are achievable the black
> magic involved has already been well done by the IC manufacturers -
> if you're not designing thousands then a dedicated IC is a better
> choice.

I've played with the Linear parts. Except for a Harris chip and a
Power Integrations chip, I haven't seen anything that can run from
more than 60V. The problem is obviously, price. If I could somehow
drop around say, 60V (@500mA) without too much heat, I could use one of the Linear switchers from
there, and Bob (Blick? ;) )would be my uncle.

 
--
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1998\12\21@000926 by Tjaart van der Walt

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Peter L. Peres wrote:
>
> On Thu, 17 Dec 1998, Tjaart van der Walt wrote:
>
> > I also have a similar question for the SMPS guru's. I've
> > been asked to re-think a design where a PIC get its power
> > from a 100V-150V DC line. How the hell does one drop
> > around 90V DC without creating an oven? I don't want to
> > use light bulbs as it is a potentially dangerous device.
>
> You can try to build a small self-oscillating SMPS with 2 transistors and
> a small ferrite core (pot + pot). Insulation will be a problem, and RFI is
> something to think about imho. For 150V input you can use medium power
> high voltage transistors designed for video amplifier duty.
>
> If you do net need galvanic separation, then the transformer can be
> replaced by a simple coil, although at this voltage ratio it does not look
> like a good idea to me, at the first sight.
>
> hope this helps,

It sure does! I've been thinking about using a PIC with some sort
of a 'bootstrap' supply to get it going. I haven't worked with DC
this high <shudder> yet, so I am on untested ground. This SMPS goes
into a 25KV DC-DC converter, so I don't want to make any mistakes
(kaboom!)


--
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1998\12\21@003802 by Bob Blick

face
flavicon
face
On Mon, 21 Dec 1998, Tjaart van der Walt wrote:
> more than 60V. The problem is obviously, price. If I could somehow
> drop around say, 60V (@500mA) without too much heat, I could use one of the Li
near switchers from
> there, and Bob (Blick? ;) )would be my uncle.

Already an uncle 10 times over, but I should really do something on this,
since I designed one that used three transistors, two LEDs, a cap and a
coil and a diode and not much else, many years ago. Made 5 volts at 5 amps
from 40 volts. I'll see what I can do. I've been smacked with work,
there've been production emergencies at work that have stretched me rather
thin.

-Bob

1998\12\21@095250 by WIL REEDER

flavicon
face
Bob Blick wrote:
>
> Already an uncle 10 times over, but I should really do something on this,
> since I designed one that used three transistors, two LEDs, a cap and a
> coil and a diode and not much else, many years ago. Made 5 volts at 5
amps
> from 40 volts. I'll see what I can do. I've been smacked with work,
> there've been production emergencies at work that have stretched me
rather
> thin.
>
> -Bob
Hi Bob
I started this thread and it sounds like you may have the solution to my
situation (need 6v at 4 watts from 12-16v input). Please let me know what
you come up with (time permitting).
Thanks


Wil Reeder
teachtechEraseMEspam.....bc.sympatico.ca
Vancouver,Canada

1998\12\21@121452 by Peter L. Peres

picon face
2-transistor switchers working off rectified mains are not exactly atomic
science. There is a book somewhere (EE curriculum from years back) that
explains most crucial things about them.

Basically, one has to add two safety features for each additional circuit
complication and expect to fry a small pile of devices before any
results are seen ;) Also wear protective glasses and don't bend too close
when energizing...

Peter

1998\12\21@132755 by Peter L. Peres

picon face
On Mon, 21 Dec 1998, WIL REEDER wrote:

> I started this thread and it sounds like you may have the solution to my
> situation (need 6v at 4 watts from 12-16v input). Please let me know what
> you come up with (time permitting).
> Thanks

TL494 + PNP switcher ? L2940 ?

hope this helps,

Peter

1998\12\22@102229 by WIL REEDER

flavicon
face
snip
If uncle Bob hasn't the time to finish the solution, you may
want to have a look at the LT1076 from Linear. I use one in
a product to give out 6V @2A from around 8V to 35V. It doesn't
even heat up.

--
Friendly Regards          /"\
                         \ /
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EraseMEtjaartspamwasp.co.za  / \ AGAINST HTML MAIL
Hi Tjaart

Thanks for your reply. These parts are clearly the solution! The National
parts are even cheaper, however, I have attempted to source these things
locally and get the min quantity 2000 story. Mail order starts with $10 for
the part $8 P&H,  $5 Customs & excise fee $5 exchange and $1 tax! This
makes it impossible to do on the one off scale. Uncle Bob has been really
good at finding workable solutions for others, I'm sure he'll come through
for me, and I'm prepared to be patient.

Many Thanks and best wishes for the holidays!

Wil Reeder
RemoveMEteachtechEraseMEspamEraseMEbc.sympatico.ca
Vancouver,Canada


'BUCK REGULATOR'
1999\01\11@144342 by Larry G. Nelson Sr.
flavicon
face
I have seen switchmode regulators made with 16C54 processors and some
analog glue so I don't see why an 84 or 508 couldn't be used.


At 08:51 AM 12/15/98 -0800, you wrote:
{Quote hidden}

Larry G. Nelson Sr.
RemoveMEL.NelsonTakeThisOuTspamspamieee.org
http://www.ultranet.com/~nr

1999\01\11@203640 by Gerhard Fiedler

picon face
i don't know... you still need the switching transistor/mosfet and a
comparator (at the very minimum), so it probably isn't getting a lot
cheaper (if at all) than a cheap switching IC (there are quite a few
around, like one oldtimer from motorola for under a us$).

but it's probably not too hard to do, if you really want it, or if you have
the pic around anyway. at 4mhz clock and 50khz switching frequency this
gives you a resolution of 5% for the PWM output, which probably is enough.

you still should take care of current limiting. hm... sounds like too much
to handle for which you can have one IC that has it all.

ge

At 14:23 01/11/99 -0500, Larry G. Nelson Sr. wrote:
{Quote hidden}

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