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'[EE]: Super cheap 5v smps regulator'
2001\12\07@064223 by Roman Black

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Hi, i've finally put that circuit and pictures up for
the super cheap 2-transistor switchmode 5v regulator
that Richard and Russell and many others contributed to
a few weeks back.

There are a couple of charts of efficiency and regulation,
and the circuit and CRO waveform. Also a great picture
of my quick coffee-table "lab setup" ha ha! :o)

It's all public domain and may be of use if you need
to run a 5v or 4v PIC from a battery with double or
triple the efficiency of a 7805 linear regulator, and
on a very tight budget. All parts are discrete and
non-critical, even the inductor, so you can use any
cheap mass produced pre-wound inductor and still
get good results.

Here it is:
http://centauri.ezy.net.au/~fastvid/smps.htm
(there are a few small pictures, about 200kb
total)
-Roman

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2001\12\07@073614 by Vasile Surducan

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Roman, I was affraid last week, you've gone in winter hollydays...
like Olin...

Cheers, Vasile

P.S. sure is not a copy of yellow.jpg ?

On Fri, 7 Dec 2001, Roman Black wrote:

{Quote hidden}

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2001\12\07@092526 by Roman Black

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Hi Vasile! :o)
No holidays, just crashed my motorcycle and
have a sore back that makes it hard to sit up
to the computer, but its 4 weeks after now
and i'm getting better. :o)
-Roman


Vasile Surducan wrote:
{Quote hidden}

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2001\12\07@194531 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Roman

   I hope you are felling better. Motorcycles can be very dangerous
sometimes. I know many people that reconsidered that option of
transportation because of the risks. Sometimes the crashes get more scary
than the fredoom fellings. Take care..

   No getting back to the SMPS. I will have an application where I will
have to make a supply with 74 volts DC input and 24 v at 300 ma and 5 v at
30 ma. I am thinking about using 2 of your 2 transistor designs modified to
the my specific needs. When I finish it I will let you and the list know how
it goes and what modifications are needed.

   You, Russel and Dave gave us one of the most interesting threads the
list has had in quite a while. I hope I can give back some information from
the gained knowledge.

Best regards,
Alexandre Guimaraes

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2001\12\07@223201 by Dave Dilatush

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Alexandre Guimarães wrote...

>    No getting back to the SMPS. I will have an application where I will
>have to make a supply with 74 volts DC input and 24 v at 300 ma and 5 v at
>30 ma. I am thinking about using 2 of your 2 transistor designs modified to
>the my specific needs. When I finish it I will let you and the list know how
>it goes and what modifications are needed.

With those voltages and currents, why not use Russell's design to step
the 74 volts down to 24, then Roman's circuit to step the 24 volts down
to 5?  Russell's circuit is probably more suited to the high-voltage
part of this thing, especially if you need 300 milliamps out of it.

Dave

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2001\12\07@223218 by Dave Dilatush

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Nice work, Roman; great write-up.

I like that "coffee-table lab" of yours.  The next step up from that
would be a lab built somewhat along the lines of this dedicated fellow's
PC setup:

http://members.home.net/dilatush/temp/extreme.jpg

Roman Black wrote...

{Quote hidden}

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2001\12\07@231103 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Dave

> With those voltages and currents, why not use Russell's design to step
> the 74 volts down to 24, then Roman's circuit to step the 24 volts down
> to 5?  Russell's circuit is probably more suited to the high-voltage
> part of this thing, especially if you need 300 milliamps out of it.

   Russel's circuit for the pre-regulator is one of the ideas I had in
mind. I will have to think it out and experiment with different options
because I will be driving just pneumatic control solenoids and the lower
voltage supply from the 24 volts. I can use some sort of current controlled
solenoid driving or a power supply controlled by the CPU because I know
exactly when I will need the power for the solenoids. To make the decision
harder I will only have one solenoid on at each time, so the current
comsuption is very previsible. The solenoids just stay on for a maximum of 9
seconds each.

   At least I have many options to choose from :-) Another problem is that
I can have some nasty spikes on the 74 Volts power line that I need to take
care.

   I will surely let the list know how it is going. After all power
supplies are the only part that is present in any of our projects :-)

Best regards,
Alexandre Guimaraes

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2001\12\08@082226 by Roman Black

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Alexandre Guimarães wrote:
>
> Hi, Roman
>
>     I hope you are felling better. Motorcycles can be very dangerous
> sometimes. I know many people that reconsidered that option of
> transportation because of the risks. Sometimes the crashes get more scary
> than the fredoom fellings. Take care..

Hi Alexandre!! Thanks for the concern. :o)
I prefer to die on my wheels than live on my
knees, sometimes safety is less important than
living life to the fullest? But at least I
wear good safety gear, my full leathers and body
armour saved me from massive injuries. You should
see what's left of my helmet, it would be perfect
to show to young motorbike riders...

>     No getting back to the SMPS. I will have an application where I will
> have to make a supply with 74 volts DC input and 24 v at 300 ma and 5 v at
> 30 ma. I am thinking about using 2 of your 2 transistor designs modified to
> the my specific needs. When I finish it I will let you and the list know how
> it goes and what modifications are needed.

Sounds like a good application. For the 5v 30mA
supply you only need a tiny cheap inductor, and
even 24v 300mA you should get away with a small
pre-wound inductor like they use in speaker
crossovers. 6x8mm and 10x14mm are commonly
available in that inductance range. I tested my
circuit to 300mA with no drama but watch the
volt ratings of your Q1 transistor.
I look forward to seeing your design! :o)

>     You, Russel and Dave gave us one of the most interesting threads the
> list has had in quite a while. I hope I can give back some information from
> the gained knowledge.

I forgot Dave! I just added his name to the web
page, sorry Dave. :o)
-Roman

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2001\12\08@082612 by Roman Black

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Dave Dilatush wrote:
>
> Nice work, Roman; great write-up.
>
> I like that "coffee-table lab" of yours.  The next step up from that
> would be a lab built somewhat along the lines of this dedicated fellow's
> PC setup:
>
> http://members.home.net/dilatush/temp/extreme.jpg


Ha ha ha!! Maybe that's a little extreme for my
tastes. :o)

Sorry I forgot to mention you on the web page it's
been fixed. As always i'm not delicate on my pages,
if ANYONE thinks something can be improved please say
so.
-Roman

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2001\12\08@082710 by Roman Black

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Dave Dilatush wrote:
>
> Alexandre Guimarães wrote...
>
> >    No getting back to the SMPS. I will have an application where I will
> >have to make a supply with 74 volts DC input and 24 v at 300 ma and 5 v at
> >30 ma. I am thinking about using 2 of your 2 transistor designs modified to
> >the my specific needs. When I finish it I will let you and the list know how
> >it goes and what modifications are needed.
>
> With those voltages and currents, why not use Russell's design to step
> the 74 volts down to 24, then Roman's circuit to step the 24 volts down
> to 5?  Russell's circuit is probably more suited to the high-voltage
> part of this thing, especially if you need 300 milliamps out of it.


I lost Russell's 3-transistor circuit, if that's
the one you're referring to, I will add it to the
page if someone can email it to me.

Just from curiosity, why Russell's circuit for the
higher voltages?
-Roman

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2001\12\08@085041 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Roman

  For the extreme guys like you falling once is never enough :-) I agree
with you, life has to be intense.. Most of us on the list get this intensity
with blowing transistor and mounting PIC's backwards ;-) If you can't drop
it than be more carefull. We like to have you around. Your sore back can get
great web pages done but try to keep it in one piece.

> I lost Russell's 3-transistor circuit, if that's
> the one you're referring to, I will add it to the
> page if someone can email it to me.
>
> Just from curiosity, why Russell's circuit for the
> higher voltages?
> -Roman

   Not higher voltages but higher currents and short circuit protection. I
will catch it on my archives and send you the email. For the 24 volts I am
very tempted to use a PWM output driving a high side bipolar drive. I will
just switch solenoids with it. For the 5 volts I will probably use your
circuit adding one more transistor to get lower ripple and using a higher
voltage rating swithing transistor. I think BD459 will get me up to 200
volts with reasonable gain. I will check it out.

Best regards,
Alexandre Guimaraes

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2001\12\10@041923 by Vasile Surducan

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On Sat, 8 Dec 2001, Dave Dilatush wrote:

> Alexandre Guimarães wrote...
>
> >    No getting back to the SMPS. I will have an application where I will
> >have to make a supply with 74 volts DC input and 24 v at 300 ma and 5 v at
> >30 ma. I am thinking about using 2 of your 2 transistor designs modified to
> >the my specific needs. When I finish it I will let you and the list know how
> >it goes and what modifications are needed.
>
> With those voltages and currents, why not use Russell's design to step
> the 74 volts down to 24, then Roman's circuit to step the 24 volts down
> to 5?  Russell's circuit is probably more suited to the high-voltage
> part of this thing, especially if you need 300 milliamps out of it.
>   I wouldn't do it like this. For me sounds like a standard switching
supply using a driver ( tl494, UC3842 ), a mosfet or bipolar switch and a
transformer, then a good rectifying diode pair and finally a filtering
stage.
To increase the efficiency the driver could be supplied directly from
output voltage after the oscillation has begun. I know that many piclisters are afraid about designing feritte core
transformers for switching supplys. So why many of you are using standard
coils. However for dedicated applications we need dedicated solutions.

Regards, Vasile

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2001\12\10@072541 by Roman Black

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Vasile Surducan wrote:
{Quote hidden}

Vasile, 24v at only 300mA is well within the
range of the cheap circuit with a pre-wound
inductor costing a few cents. Two transistors,
cheap inductor, no need for a chip or otherwise.
I've spent years winding ferrites too and its
nice sometimes not to have to do it. :o)

If REAL efficiency is needed I would PWM the
solenoids direct like Alexandre suggested, as
you can give them full current for just long
enough to "pull-in" and about 1/3 the current
for holding. I have a one R one C circuit
that does this that i've been using for many
years, (but with the added PWM this would get
very very efficient for solenoid driving.)

The non-pwm circuit:

+ ---R-------------
        |        |
        |        |
        |        SOL(+diode)
        |        |
        C        |
        |        |
        |        Transistor
        |        |
- -----------------

This circuit allows full 12v etc to pull-in
the 12v solenoid, and you simply choose the
R value to give enough holding current. You can
hold a 12v 100mA solenoid reliably with about
35mA, and just make sure C is big enough to
provide the pull-in energy. I invented this
when I was about 12 playing with my first
large solenoid. I don't think i've ever used
a solenoid since without doing this, AND its
great for keeping solenoid hash away from your
PSU. :o)
-Roman

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2001\12\10@081001 by Vasile Surducan

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On Mon, 10 Dec 2001, Roman Black wrote:

{Quote hidden}

 Roman, 70V to 24V and 24V to 5V using two separate supplys, sound for me a little strange
even at 300mA.
One transformer with two output coils, one for +24V ( and/or driver) and another for +5V sounds
better. At this current, efficiency of up to 85%...90% can be easily obtained. The solenoid ( or transformer as I suggested, to isolate the output ) is not a big deal, small
core, tiny wires. A HV driver can drive directly
the transformer. Resonant solution may minimise the input current and increase the efficiency.
Just a thought, don't kill me [grin]
I'm glad you're OK.
Vasile
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2001\12\10@092648 by Roman Black

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Vasile Surducan wrote:

{Quote hidden}

Sure. But winding a dual output former is
scary for some people and always takes time
to wind it and tune it. Then which rail do you
regulate? The 5v is only 30mA and regulating that
one will allow the 24v 300mA to be very sloppy.
Or regulate the 24v rail and use a 7805 etc
for the 5v rail? That's 2 chips and a special
transformer now. :o)

I just got a smile from the thought the
2-transistor circuit we all worked on might get
used for a "real" project ha ha! :o)

> Just a thought, don't kill me [grin]
> I'm glad you're OK.

Thanks for the concern! :o)
I don't kill people, well maybe if you get on
the back of my bike ha ha!! Seriously I ride
VERY safe with a passenger.

Did you like my RC solenoid driver circuit?
-Roman

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2001\12\10@094120 by Batchellor, Gary

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Looking for a high current 12v and 5v solution. Somewhere around 10amps 12v
and 3 amps 5v. Suggestions? Understanding this may be a bit more expensive
than cheap.




Vasile Surducan wrote:

{Quote hidden}

Sure. But winding a dual output former is
scary for some people and always takes time
to wind it and tune it. Then which rail do you
regulate? The 5v is only 30mA and regulating that
one will allow the 24v 300mA to be very sloppy.
Or regulate the 24v rail and use a 7805 etc
for the 5v rail? That's 2 chips and a special
transformer now. :o)

I just got a smile from the thought the
2-transistor circuit we all worked on might get
used for a "real" project ha ha! :o)

> Just a thought, don't kill me [grin]
> I'm glad you're OK.

Thanks for the concern! :o)
I don't kill people, well maybe if you get on
the back of my bike ha ha!! Seriously I ride
VERY safe with a passenger.

Did you like my RC solenoid driver circuit?
-Roman

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2001\12\10@095020 by Roman Black

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Batchellor, Gary wrote:
>
> Looking for a high current 12v and 5v solution. Somewhere around 10amps 12v
> and 3 amps 5v. Suggestions? Understanding this may be a bit more expensive
> than cheap.


What total current range? Down to zero amps?
How much regulation needed? Input voltage?
Efficiency needs?
-Roman

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2001\12\10@095655 by Batchellor, Gary

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The 12v will be occasional loading (motors), so it will be 10amps or
nothing. The 5v will be from a low of .5a to a max of 3a.

{Original Message removed}

2001\12\10@100825 by Batchellor, Gary

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Sorry I left out some of the info.  What total current range? The 12v will
be occasional loading (motors), so it will be 10amps or
nothing. The 5v will be from a low of .5a to a max of 3a. Down to zero amps?
On the 12v side but the 5v no.
How much regulation needed? Regulation can be a bit sloppy especially on the
12v side. The 5v I would like to keep within about .3 +/- Input voltage? 24v
to 36v dc
Efficiency needs? This isn't a big concern right now.

{Original Message removed}

2001\12\10@102826 by Roman Black

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Batchellor, Gary wrote:
>
> Sorry I left out some of the info.  What total current range? The 12v will
> be occasional loading (motors), so it will be 10amps or
> nothing. The 5v will be from a low of .5a to a max of 3a. Down to zero amps?
> On the 12v side but the 5v no.
> How much regulation needed? Regulation can be a bit sloppy especially on the
> 12v side. The 5v I would like to keep within about .3 +/- Input voltage? 24v
> to 36v dc
> Efficiency needs? This isn't a big concern right now.


I suggest driving the motors via PWM directly from
the 24v or 36v side. You can use the same FETs
with no 12v PSU needed, less parts, better efficiency,
and much higher motor performance available.
Stepper motors and good DC servos are almost always
driven this way.

The 5v up to 3A is do-able with the 2-tran one
inductor circuit, with the right transistor
choices. BUT this project sounds expensive in total,
the obvious choice would be a dedicated 5v smps
regulator chip, and the chip specs would have
charts suggesting a good inductor size and type
saving you some research.

Is it a robot?
-Roman

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2001\12\10@105632 by Batchellor, Gary

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This is a quasi home automation type project for HVAC. It will be driving
some damper doors open or closed depending on temp, turning on or off
heating/a.c., sensing air flows and a humidity device thrown in.

{Original Message removed}

2001\12\11@072230 by Roman Black

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Thats an important point. So you probably won't
need fine control of motor speed and positioning?
If you can get by with 12v to your motors via simple
relay and end-travel switches then driving the motors
by PWM is a complication you just don't need.
So why do you need to convert 36v to drive the motors?
If it is for an air conditioning application can't
you just use a 12v mains transformer of suitable
current ability?
-Roman


Batchellor, Gary wrote:
{Quote hidden}

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2001\12\11@082515 by Batchellor, Gary

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Overlooked the obvious, since they are dc motors just take a really big
xformer and rectify it, ripple is no problem. Have to see how that works.

{Original Message removed}

2001\12\11@165957 by Peter L. Peres

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> Looking for a high current 12v and 5v solution. Somewhere around
> 10amps 12v and 3 amps 5v. Suggestions? Understanding this may be a bit
> more expensive than cheap.

This is 120W or 15W. There is a big difference. A 15W regulator can be
done with one of the 'simple switcher' chips pushed to near its limits.
The 120W one is a different story imho.

Peter

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