🚀 go-pugleaf

On Mon, 09 Jun 2008 22:42:37 +1000 F Murtz <haggisz@hotmail.com> wrote in
Message id: <484d2532@dnews.tpgi.com.au>:

>I would like to make an adjustable power supply using a transformer with 
>a 24v 5a single wound secondary I would like the voltage to be 
>adjustable from lowest to highest possible given transformer I would 
>like to have regulated current
>
>There is another possibility I also have a larger transformer with two 
>32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>supply with adjustable current regulation making the most of the 
>transformer specs I would be eternally grateful

How about this one: http://www.national.com/mpf/LM/LM1084.html

On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
> I would like to make an adjustable power supply using a transformer with
> a 24v 5a single wound secondary I would like the voltage to be
> adjustable from lowest to highest possible given transformer I would
> like to have regulated current
>
> There is another possibility I also have a larger transformer with two
> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> supply with adjustable current regulation making the most of the
> transformer specs I would be eternally grateful


How much current do you want?

Lets just assume you make DC from the AC and then regulate down.

Doing a couple of figures for making 4A into lets say zero volts:

24V * sqrt(2) = 34V

34V * 4A = 136W

The the regulator circuit needs to get rid of 136W.

To do this, you need something like 10 TO-220 packages transistors
screwed down to a quite large chunk of fins.

If you have enough fin area, about 5 to 7 TIP-35 or TIP-36 transistors
would work for you.

Another question is how fast the current limiting or regulation needs
to act.  A lot of very practical designs can make a large spike of
current when suddenly shorted.  The power supply will easily survive
this but if the short was you connecting it to a diode, the diode may
be damaged.

Do you need instant (or nearly so) action on the current limiting?

Take a look at the LT3080:
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1040,C1055,P38503

Notice how it lets you set the output voltage all the way down to
zero.  This sort of design is a good place to start your thinking.

You can also think of the circuit as just a non-inverting op-amp
amplifying the output of the pot you use to set the voltage.  This is
another good direction to go.

F Murtz wrote:
> I would like to make an adjustable power supply using a transformer with 
> a 24v 5a single wound secondary I would like the voltage to be 
> adjustable from lowest to highest possible given transformer I would 
> like to have regulated current
> 
> There is another possibility I also have a larger transformer with two 
> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
> supply with adjustable current regulation making the most of the 
> transformer specs I would be eternally grateful

Regulated current or regulated voltage?  Or do you want a lab-type 
supply with regulated voltage and smooth current limiting?

It sounds like you don't have a tremendous amount of experience with 
electronics -- you may find it helpful to get a copy of the ARRL 
handbook, which has some nice power supply designs as well as a _lot_ of 
good practical basic knowledge.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Snip
">
> Regulated current or regulated voltage?  Or do you want a lab-type supply 
> with regulated voltage and smooth current limiting?
>
> It sounds like you don't have a tremendous amount of experience with 
> electronics -- you may find it helpful to get a copy of the ARRL handbook, 
> which has some nice power supply designs as well as a _lot_ of good 
> practical basic knowledge.
>
> -- 
>
> Tim Wescott
> Wescott Design Services
> http://www.wescottdesign.com

My guess is it's for a glow plug in an RC model engine.... so regulated 
voltage, current limited. 

"TT_Man" <Someone@ntlworld.com> wrote in message 
news:4Bc3k.157718$cZ3.152377@newsfe10.ams2...
> Snip
> ">
>> Regulated current or regulated voltage?  Or do you want a lab-type supply 
>> with regulated voltage and smooth current limiting?
>>
>> It sounds like you don't have a tremendous amount of experience with 
>> electronics -- you may find it helpful to get a copy of the ARRL 
>> handbook, which has some nice power supply designs as well as a _lot_ of 
>> good practical basic knowledge.
>>
>> -- 
>>
>> Tim Wescott
>> Wescott Design Services
>> http://www.wescottdesign.com
>
> My guess is it's for a glow plug in an RC model engine.... so regulated 
> voltage, current limited.
Oops, forget I said that. :( 

In article <484d2532@dnews.tpgi.com.au>, F Murtz wrote:

>I would like to make an adjustable power supply using a transformer with 
>a 24v 5a single wound secondary I would like the voltage to be 
>adjustable from lowest to highest possible given transformer I would 
>like to have regulated current
>
>There is another possibility I also have a larger transformer with two 
>32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>supply with adjustable current regulation making the most of the 
>transformer specs I would be eternally grateful

  One thing to watch for:  RMS current being drawn from the transformer 
exceeding the DC output current.  The bigger the filter capacitor, the 
worse this gets.

  Assuming that you will be using an adjustable voltage regulator, you 
should be OK with a few volts of filter capacitor ripple, so don't make 
the filter capacitors too big.

  I would not try for more than 3-4 amps of DC from a 5 amp transformer 
unless the rating is for achievable DC with a "capacitor input" 
rectifier/filter circuit (capacitor immediately following the rectifier, 
as opposed to having a choke between the rectifier and the capacitor).

  24 volts times sqr(2) is 33.9 volts.  Allow loss of a couple volts in 
a bridge rectifier, a couple volts minimum drop in a voltage regulator 
that is doing its job well, a couple more for a current regulator, and 
that is about 28 volts.  Allow 4 volts ripple on a moderate filter 
capacitor, and you get 24 volts.

  As for a filter capacitor value:  4 volts ripple at 4 amps over the 
approx. 6 milliseconds or so that the capacitor has to supply current
works out to 6,000 microfarads.  I would not use more.  Greater filter 
capacitance makes the current waveform drawn from the transformer spikier, 
which makes the RMS current drawn from the transformer greater.  I might 
go for 4700 microfarads and only count on drawing 3-3.5 amps DC without 
overheating the transformer.

  BEWARE - with mild-moderate overloads, transformers this size can take a 
couple hours to reach excessive temperature.

 - Don Klipstein (don@misty.com)

"Don Klipstein"

>  One thing to watch for:  RMS current being drawn from the transformer
> exceeding the DC output current.  The bigger the filter capacitor, the
> worse this gets.


** That last claim is   ABSOLUTE   BULLSHIT  !!!!

Nothing new for this ignorant, septic asshole to make them.


>  Assuming that you will be using an adjustable voltage regulator, you
> should be OK with a few volts of filter capacitor ripple, so don't make
> the filter capacitors too big.


** Make it as big as you like and the rms ripple current will not increase.


>  As for a filter capacitor value:  4 volts ripple at 4 amps over the
> approx. 6 milliseconds or so that the capacitor has to supply current
> works out to 6,000 microfarads.  I would not use more.  Greater filter
> capacitance makes the current waveform drawn from the transformer spikier,


** No it does not !!

The whole idea is an idiotic  MYTH  put about by complete fools like 
Klipstein.


> which makes the RMS current drawn from the transformer greater.  I might
> go for 4700 microfarads and only count on drawing 3-3.5 amps DC without
> overheating the transformer.


** 20,000 uF would be a good value to use -  cos increasing the filter 
capacitance above the minimum usable value has no effect on the rms current 
in the transformer windings.


......   Phil

On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensmith@rahul.net> wrote:

>On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
>> I would like to make an adjustable power supply using a transformer with
>> a 24v 5a single wound secondary I would like the voltage to be
>> adjustable from lowest to highest possible given transformer I would
>> like to have regulated current
>>
>> There is another possibility I also have a larger transformer with two
>> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
>> supply with adjustable current regulation making the most of the
>> transformer specs I would be eternally grateful
>
>
>How much current do you want?
>
>Lets just assume you make DC from the AC and then regulate down.
>
>Doing a couple of figures for making 4A into lets say zero volts:
>
>24V * sqrt(2) = 34V
>
>34V * 4A = 136W
>
>The the regulator circuit needs to get rid of 136W.

Minor points - the transformer isn't rated to deliver 136W, and that 34V is
unloaded peak.

On Jun 9, 6:32 pm, rebel <m...@privacy.net> wrote:
> On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
> >> I would like to make an adjustable power supply using a transformer with
> >> a 24v 5a single wound secondary I would like the voltage to be
> >> adjustable from lowest to highest possible given transformer I would
> >> like to have regulated current
>
> >> There is another possibility I also have a larger transformer with two
> >> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> >> supply with adjustable current regulation making the most of the
> >> transformer specs I would be eternally grateful
>
> >How much current do you want?
>
> >Lets just assume you make DC from the AC and then regulate down.
>
> >Doing a couple of figures for making 4A into lets say zero volts:
>
> >24V * sqrt(2) = 34V
>
> >34V * 4A = 136W
>
> >The the regulator circuit needs to get rid of 136W.
>
> Minor points - the transformer isn't rated to deliver 136W, and that 34V is
> unloaded peak.

When working out the power in the regulator, it is best to assume that
the peak voltage is what you get.  The rated voltage on the
transformer is for a normal line voltage.  In the high line case, you
can get a little more.

On Tue, 10 Jun 2008 06:36:46 -0700 (PDT), MooseFET <kensmith@rahul.net> wrote:

>On Jun 9, 6:32 pm, rebel <m...@privacy.net> wrote:
>> On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
>> >On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
>> >> I would like to make an adjustable power supply using a transformer with
>> >> a 24v 5a single wound secondary I would like the voltage to be
>> >> adjustable from lowest to highest possible given transformer I would
>> >> like to have regulated current
>>
>> >> There is another possibility I also have a larger transformer with two
>> >> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
>> >> supply with adjustable current regulation making the most of the
>> >> transformer specs I would be eternally grateful
>>
>> >How much current do you want?
>>
>> >Lets just assume you make DC from the AC and then regulate down.
>>
>> >Doing a couple of figures for making 4A into lets say zero volts:
>>
>> >24V * sqrt(2) = 34V
>>
>> >34V * 4A = 136W
>>
>> >The the regulator circuit needs to get rid of 136W.
>>
>> Minor points - the transformer isn't rated to deliver 136W, and that 34V is
>> unloaded peak.
>
>When working out the power in the regulator, it is best to assume that
>the peak voltage is what you get.  The rated voltage on the
>transformer is for a normal line voltage.  In the high line case, you
>can get a little more.

I appreciate that, but my original comments stand.  There is no valid reason to
state "the regulator circuit needs to get rid of 136W" when the transformer is
not rated to deliver that power.

F Murtz wrote:
> I would like to make an adjustable power supply using a transformer with 
> a 24v 5a single wound secondary I would like the voltage to be 
> adjustable from lowest to highest possible given transformer I would 
> like to have regulated current
> 
> There is another possibility I also have a larger transformer with two 
> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
> supply with adjustable current regulation making the most of the 
> transformer specs I would be eternally grateful


Thanks to every one for their help on power supply design from spec 
sheets etc but I was hoping for an already designed circuit

"F Murtz" <haggisz@hotmail.com>

**Beware  -   cross-posting Hotmail wanker on the loose....


> Thanks to every one for their help on power supply design from spec sheets 
> etc but I was hoping for an already designed circuit


** Do you still expect to get visits from the " tooth fairy "   ???




.....  Phil

Phil Allison wrote:
> "F Murtz" <haggisz@hotmail.com>
> 
> **Beware  -   cross-posting Hotmail wanker on the loose....
> 
> 
>> Thanks to every one for their help on power supply design from spec sheets 
>> etc but I was hoping for an already designed circuit
> 
> 
> ** Do you still expect to get visits from the " tooth fairy "   ???
> 
> 
> 
> 
> .....  Phil
> 
> 
Phil very sorry if cross posting is illegal but I thought different 
people used different ngs other wise there would be only one and I 
thought I would reach a greater audience.
If the only way to obtain a circuit for a power supply is to get a 
degree in everything I suppose I should instead of asking on news groups

"F Murtz" <haggisz@hotmail.com>
>
>> **Beware  -   cross-posting Hotmail wanker on the loose....
>>
>>
>>> Thanks to every one for their help on power supply design from spec 
>>> sheets etc but I was hoping for an already designed circuit
>>
>>
>> ** Do you still expect to get visits from the " tooth fairy "   ???
>>
>>
>>
> Phil very sorry if cross posting is illegal but I thought different people 
> used different ngs other wise there would be only one and I thought I 
> would reach a greater audience.


** Yes dickhead  -   I do know why people cross post.

But it is the act of a troll and tedious Hotmail wankers who have no common 
sense.


> If the only way to obtain a circuit for a power supply is to get a degree 
> in everything I suppose I should instead of asking on news groups


** Someone as stupid as you will never learn anything.

  Cos you ignore everything you don't want to hear.



.....  Phil

"F Murtz" <haggisz@hotmail.com> wrote in message 
news:484F3906.4080401@hotmail.com...
> Phil Allison wrote:
>> "F Murtz" <haggisz@hotmail.com>
>>
>> **Beware  -   cross-posting Hotmail wanker on the loose....
>>
>>
>>> Thanks to every one for their help on power supply design from spec 
>>> sheets etc but I was hoping for an already designed circuit
>>
>>
>> ** Do you still expect to get visits from the " tooth fairy "   ???
>>
>>
>>
>>
>> .....  Phil
>>
>>
> Phil very sorry if cross posting is illegal but I thought different people 
> used different ngs other wise there would be only one and I thought I 
> would reach a greater audience.
> If the only way to obtain a circuit for a power supply is to get a degree 
> in everything I suppose I should instead of asking on news groups.

Your first clue and News Groups life lesson is to ignore Phil and his 
obsessive compulsive disorder driven, vitriol. (Killfile him, and your NG 
life will be so much more pleasureable)

On Wed, 11 Jun 2008 11:24:33 +1000, F Murtz <haggisz@hotmail.com>
wrote:

>F Murtz wrote:
>> I would like to make an adjustable power supply using a transformer with 
>> a 24v 5a single wound secondary I would like the voltage to be 
>> adjustable from lowest to highest possible given transformer I would 
>> like to have regulated current
>> 
>> There is another possibility I also have a larger transformer with two 
>> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>> supply with adjustable current regulation making the most of the 
>> transformer specs I would be eternally grateful
>
>
>Thanks to every one for their help on power supply design from spec 
>sheets etc but I was hoping for an already designed circuit

It would be a pity, putting together your first power supply without
taking the oportunity to learn something about it. I mean - what are
you going to be using the completed power supply for, if not as a
learning tool?

A fair supply of app notes are available on the web to help you do
this, in consideration of the fact that you want to tailor the circuit
to transformers that you already have. Normally you wouldn't purchase
a part before you had some idea of what you needed, to do what you
aimed to do.

http://www.ieeta.pt/~alex/docs/ApplicationNotes/Rectifier%20Applications%20Handbook.pdf

A kit or pre-built/surplus unit may be an obvious alternative to the
bulk of all this 'learning' stuff. Even then, getting what you need
still requires an aim, to specify a requirement.

One kind of regulation method that is fairly tolerant of transformer
fixed winding voltages is illustrated at 

http://members.shaw.ca/legg/1991a.html

This also offers a pspice simulation that runs in the free SWCADIII
package from Linear Technology. It takes a lot more savy to graft
regulation circuits onto un-anticipated transformers than it does to
design for a transformer from scratch, or fit a properly configured
transformer into a pre-designed configuration. 

RL

legg wrote:
> On Wed, 11 Jun 2008 11:24:33 +1000, F Murtz <haggisz@hotmail.com>
> wrote:
> 
>> F Murtz wrote:
>>> I would like to make an adjustable power supply using a transformer with 
>>> a 24v 5a single wound secondary I would like the voltage to be 
>>> adjustable from lowest to highest possible given transformer I would 
>>> like to have regulated current
>>>
>>> There is another possibility I also have a larger transformer with two 
>>> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>>> supply with adjustable current regulation making the most of the 
>>> transformer specs I would be eternally grateful
>>
>> Thanks to every one for their help on power supply design from spec 
>> sheets etc but I was hoping for an already designed circuit
> 
> It would be a pity, putting together your first power supply without
> taking the oportunity to learn something about it. I mean - what are
> you going to be using the completed power supply for, if not as a
> learning tool?
> 
> A fair supply of app notes are available on the web to help you do
> this, in consideration of the fact that you want to tailor the circuit
> to transformers that you already have. Normally you wouldn't purchase
> a part before you had some idea of what you needed, to do what you
> aimed to do.
> 
> http://www.ieeta.pt/~alex/docs/ApplicationNotes/Rectifier%20Applications%20Handbook.pdf
> 
> A kit or pre-built/surplus unit may be an obvious alternative to the
> bulk of all this 'learning' stuff. Even then, getting what you need
> still requires an aim, to specify a requirement.
> 
> One kind of regulation method that is fairly tolerant of transformer
> fixed winding voltages is illustrated at 
> 
> http://members.shaw.ca/legg/1991a.html
> 
> This also offers a pspice simulation that runs in the free SWCADIII
> package from Linear Technology. It takes a lot more savy to graft
> regulation circuits onto un-anticipated transformers than it does to
> design for a transformer from scratch, or fit a properly configured
> transformer into a pre-designed configuration. 
> 
> RL
Thanks I will look into what you have said.
The reason for using these transformers is that I already have them. I 
did not buy them They were disused equipment

"F Murtz"
>
> >It takes a lot more savy to graft
>> regulation circuits onto un-anticipated transformers than it does to
>> design for a transformer from scratch, or fit a properly configured
>> transformer into a pre-designed configuration.
> Thanks I will look into what you have said.
> The reason for using these transformers is that I already have them. I did 
> not buy them They were disused equipment


**  We  BLOODY  know that  -  you steaming great half-wit.

 Got any sows ears you want to make into purses  ??





.....  Phil

On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
> I would like to make an adjustable power supply using a transformer with
> a 24v 5a single wound secondary I would like the voltage to be
> adjustable from lowest to highest possible given transformer I would
> like to have regulated current
>
> There is another possibility I also have a larger transformer with two
> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> supply with adjustable current regulation making the most of the
> transformer specs I would be eternally grateful

Look up the LM338 three terminal regulator. It's rated at 5 amps and
35 volts from output to input. All you need is a couple resistors or a
pot to set the output voltage. Use a 10 amp bridge rectifier to
convert the transformer secondary AC to DC and a 20,000uF, or
thereabouts filter cap. Connect the capacitor to the (+) input of the
regulator and ground and adjust the resistors for the desired output
votage. The regulator also has current limiting, but not sure what it
is. You can get 1.2 volts to maybe 24 volts DC out, but you need a
large heat sink   when the output is set low and drawing 5 amps.

-Bill

Phil Allison wrote:
> "F Murtz"
>>> It takes a lot more savy to graft
>>> regulation circuits onto un-anticipated transformers than it does to
>>> design for a transformer from scratch, or fit a properly configured
>>> transformer into a pre-designed configuration.
>> Thanks I will look into what you have said.
>> The reason for using these transformers is that I already have them. I did 
>> not buy them They were disused equipment
> 
> 
> **  We  BLOODY  know that  -  you steaming great half-wit.
> 
>  Got any sows ears you want to make into purses  ??
> 
> 
> 
> 
> 
> .....  Phil
> 
> 
> 
I do not know what your problem is but I was explaining the free 
transformers to Legg who seemed to think that I bought the transformers 
and then wanted a circuit

>> "F Murtz"
>>>> It takes a lot more savy to graft
>>>> regulation circuits onto un-anticipated transformers than it does to
>>>> design for a transformer from scratch, or fit a properly configured
>>>> transformer into a pre-designed configuration.
>>> Thanks I will look into what you have said.
>>> The reason for using these transformers is that I already have them. I 
>>> did not buy them They were disused equipment
>>
>>
>> **  We  BLOODY  know that  -  you steaming great half-wit.
>>
>>  Got any sows ears you want to make into purses  ??
>>
>>
>>
> I do not know what your problem is


** YOU are the one with all the problems  -   dickhead.

 but I was explaining the free
> transformers to Legg who seemed to think that I bought the transformers 
> and then wanted a circuit


**  Yet another of your mindless false assumptions.

   Go away,  fool.



....   Phil

On Wed, 11 Jun 2008 14:29:43 +1000, F Murtz <haggisz@hotmail.com>
wrote:

>legg wrote:
>> On Wed, 11 Jun 2008 11:24:33 +1000, F Murtz <haggisz@hotmail.com>
>> wrote:
>> 
>>> F Murtz wrote:
>>>> I would like to make an adjustable power supply using a transformer with 
>>>> a 24v 5a single wound secondary I would like the voltage to be 
>>>> adjustable from lowest to highest possible given transformer I would 
>>>> like to have regulated current
>>>>
>>>> There is another possibility I also have a larger transformer with two 
>>>> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>>>> supply with adjustable current regulation making the most of the 
>>>> transformer specs I would be eternally grateful
>>>
>>> Thanks to every one for their help on power supply design from spec 
>>> sheets etc but I was hoping for an already designed circuit
<snip
>> A fair supply of app notes are available on the web to help you do
>> this, in consideration of the fact that you want to tailor the circuit
>> to transformers that you already have. Normally you wouldn't purchase
>> a part before you had some idea of what you needed, to do what you
>> aimed to do.
>> 
>> http://www.ieeta.pt/~alex/docs/ApplicationNotes/Rectifier%20Applications%20Handbook.pdf
>> 
<snip>
>Thanks I will look into what you have said.
>The reason for using these transformers is that I already have them. I 
>did not buy them They were disused equipment

The Motorola handbook will give a good idea about what your
transformers are capable of, and how they might be configured to give
different output voltages to suit a post regulator. That will be your
first step, and give you your options.

RL

On Jun 10, 11:21 pm, Bill Bowden <wrongaddr...@att.net> wrote:
> On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
>
> > I would like to make an adjustable power supply using a transformer with
> > a 24v 5a single wound secondary I would like the voltage to be
> > adjustable from lowest to highest possible given transformer I would
> > like to have regulated current
>
> > There is another possibility I also have a larger transformer with two
> > 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> > supply with adjustable current regulation making the most of the
> > transformer specs I would be eternally grateful
>
> Look up the LM338 three terminal regulator. It's rated at 5 amps and
> 35 volts from output to input.

But certainly not at the same time:

http://www.national.com/mpf/LM/LM338.html


> All you need is a couple resistors or a
> pot to set the output voltage. Use a 10 amp bridge rectifier to
> convert the transformer secondary AC to DC and a 20,000uF, or
> thereabouts filter cap. Connect the capacitor to the (+) input of the
> regulator and ground and adjust the resistors for the desired output
> votage. The regulator also has current limiting, but not sure what it
> is. You can get 1.2 volts to maybe 24 volts DC out, but you need a
> large heat sink   when the output is set low and drawing 5 amps.

Go read the datasheet before you believe this last bit.

Earlier, I posted the simple math that suggests that you want about 10
TO-220 packaged transistors to get that much power.


Here's a bit of ascii art for a way to share the power around:

                      NPN     R4
     -----------------   ----/\/\----
    !              Q2 \ /e           !
    !                 ---            !
    !  R2    PNP       !      R3     !
    +-/\/\---   -------+-----/\/\----+
    !       e\ / Q1                  !
    !        ---     U1              !
    !   R1    !      -------         !
  --+--\/\/---+-----! LM317 !----+---+---
                     -------     !
                        !        !
                        +-/\/\---
                        !
                        \
                        /
                        \
                        !
                       GND

The capacitors have been left out because I am too lazy to do them.

When U1 draws current R1 develops a voltage due to Ohms law.  Once
Q1's e-b draw is overcome, R2 sets how much voltage is needed on R1
per mA flowing in Q1.

R3 and R4 repeat the trick.  If you set the resistor values correctly,
you can spread the full load power over the three devices.

To get 10 or so devices, the Q2 R4 circuit becomes several transistors
each with its own emitter resistor.



>
> -Bill

F Murtz wrote:
> F Murtz wrote:
> 
>> I would like to make an adjustable power supply using a transformer 
>> with a 24v 5a single wound secondary I would like the voltage to be 
>> adjustable from lowest to highest possible given transformer I would 
>> like to have regulated current
>>
>> There is another possibility I also have a larger transformer with two 
>> 32v 4.7a secondaries If anyone has a schematic for an adjustable power 
>> supply with adjustable current regulation making the most of the 
>> transformer specs I would be eternally grateful
> 
> 
> 
> Thanks to every one for their help on power supply design from spec 
> sheets etc but I was hoping for an already designed circuit

In a reply in another neswgroup someone recommended that you
look in the ARRL handbook; it was also suggested that you look
at an Astron power supply schematic at repeater-builder.com
http://www.repeater-builder.com/astron/pdfs/seits-astron-article.pdf
Both sources give you what you want - a schematic of an
already designed circuit. You can modify the designs as
necessary to suit your needs.

Ed

On Wed, 11 Jun 2008 03:07:12 GMT, "-=Spudley=-" <-=Spudley=-@work.com>
wrote:

>
>"F Murtz" <haggisz@hotmail.com> wrote in message 
>news:484F3906.4080401@hotmail.com...
>> Phil Allison wrote:
>>> "F Murtz" <haggisz@hotmail.com>
>>>
>>> **Beware  -   cross-posting Hotmail wanker on the loose....
>>>
>>>
>>>> Thanks to every one for their help on power supply design from spec 
>>>> sheets etc but I was hoping for an already designed circuit
>>>
>>>
>>> ** Do you still expect to get visits from the " tooth fairy "   ???
>>>
>>>
>>>
>>>
>>> .....  Phil
>>>
>>>
>> Phil very sorry if cross posting is illegal but I thought different people 
>> used different ngs other wise there would be only one and I thought I 
>> would reach a greater audience.
>> If the only way to obtain a circuit for a power supply is to get a degree 
>> in everything I suppose I should instead of asking on news groups.
>
>Your first clue and News Groups life lesson is to ignore Phil and his 
>obsessive compulsive disorder driven, vitriol. (Killfile him, and your NG 
>life will be so much more pleasureable)
>

Much agreed, I do as well.
  

"JosephKrautKunthead "


>
> Much agreed, I do as well.


**   Fuck off   -  you  PITA  brain dead troll.




....   Phil 

On Jun 10, 4:26 pm, rebel <m...@privacy.net> wrote:
> On Tue, 10 Jun 2008 06:36:46 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >On Jun 9, 6:32 pm, rebel <m...@privacy.net> wrote:
> >> On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >> >On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
> >> >> I would like to make an adjustable power supply using a transformer with
> >> >> a 24v 5a single wound secondary I would like the voltage to be
> >> >> adjustable from lowest to highest possible given transformer I would
> >> >> like to have regulated current
>
> >> >> There is another possibility I also have a larger transformer with two
> >> >> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> >> >> supply with adjustable current regulation making the most of the
> >> >> transformer specs I would be eternally grateful
>
> >> >How much current do you want?
>
> >> >Lets just assume you make DC from the AC and then regulate down.
>
> >> >Doing a couple of figures for making 4A into lets say zero volts:
>
> >> >24V * sqrt(2) = 34V
>
> >> >34V * 4A = 136W
>
> >> >The the regulator circuit needs to get rid of 136W.
>
> >> Minor points - the transformer isn't rated to deliver 136W, and that 34V is
> >> unloaded peak.
>
> >When working out the power in the regulator, it is best to assume that
> >the peak voltage is what you get.  The rated voltage on the
> >transformer is for a normal line voltage.  In the high line case, you
> >can get a little more.
>
> I appreciate that, but my original comments stand.  There is no valid reason to
> state "the regulator circuit needs to get rid of 136W" when the transformer is
> not rated to deliver that power.

You seem to have a poor understand of what the rating of a transformer
means.

On Sat, 14 Jun 2008 07:48:55 -0700 (PDT), MooseFET <kensmith@rahul.net> wrote:

>On Jun 10, 4:26 pm, rebel <m...@privacy.net> wrote:
>> On Tue, 10 Jun 2008 06:36:46 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
>> >On Jun 9, 6:32 pm, rebel <m...@privacy.net> wrote:
>> >> On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
>> >> >On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
>> >> >> I would like to make an adjustable power supply using a transformer with
>> >> >> a 24v 5a single wound secondary I would like the voltage to be
>> >> >> adjustable from lowest to highest possible given transformer I would
>> >> >> like to have regulated current
>>
>> >> >> There is another possibility I also have a larger transformer with two
>> >> >> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
>> >> >> supply with adjustable current regulation making the most of the
>> >> >> transformer specs I would be eternally grateful
>>
>> >> >How much current do you want?
>>
>> >> >Lets just assume you make DC from the AC and then regulate down.
>>
>> >> >Doing a couple of figures for making 4A into lets say zero volts:
>>
>> >> >24V * sqrt(2) = 34V
>>
>> >> >34V * 4A = 136W
>>
>> >> >The the regulator circuit needs to get rid of 136W.
>>
>> >> Minor points - the transformer isn't rated to deliver 136W, and that 34V is
>> >> unloaded peak.
>>
>> >When working out the power in the regulator, it is best to assume that
>> >the peak voltage is what you get.  The rated voltage on the
>> >transformer is for a normal line voltage.  In the high line case, you
>> >can get a little more.
>>
>> I appreciate that, but my original comments stand.  There is no valid reason to
>> state "the regulator circuit needs to get rid of 136W" when the transformer is
>> not rated to deliver that power.
>
>You seem to have a poor understand of what the rating of a transformer
>means.

On the contrary.  A 24V 5A secondary is rated for 120VA.  Your education
suggests something different?  Please inform us all as to YOUR transformer
theory.

On Jun 14, 9:29 pm, rebel <m...@privacy.net> wrote:
> On Sat, 14 Jun 2008 07:48:55 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >On Jun 10, 4:26 pm, rebel <m...@privacy.net> wrote:
> >> On Tue, 10 Jun 2008 06:36:46 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >> >On Jun 9, 6:32 pm, rebel <m...@privacy.net> wrote:
> >> >> On Mon, 9 Jun 2008 07:55:58 -0700 (PDT), MooseFET <kensm...@rahul.net> wrote:
> >> >> >On Jun 9, 5:42 am, F Murtz <hagg...@hotmail.com> wrote:
> >> >> >> I would like to make an adjustable power supply using a transformer with
> >> >> >> a 24v 5a single wound secondary I would like the voltage to be
> >> >> >> adjustable from lowest to highest possible given transformer I would
> >> >> >> like to have regulated current
>
> >> >> >> There is another possibility I also have a larger transformer with two
> >> >> >> 32v 4.7a secondaries If anyone has a schematic for an adjustable power
> >> >> >> supply with adjustable current regulation making the most of the
> >> >> >> transformer specs I would be eternally grateful
>
> >> >> >How much current do you want?
>
> >> >> >Lets just assume you make DC from the AC and then regulate down.
>
> >> >> >Doing a couple of figures for making 4A into lets say zero volts:
>
> >> >> >24V * sqrt(2) = 34V
>
> >> >> >34V * 4A = 136W
>
> >> >> >The the regulator circuit needs to get rid of 136W.
>
> >> >> Minor points - the transformer isn't rated to deliver 136W, and that 34V is
> >> >> unloaded peak.
>
> >> >When working out the power in the regulator, it is best to assume that
> >> >the peak voltage is what you get.  The rated voltage on the
> >> >transformer is for a normal line voltage.  In the high line case, you
> >> >can get a little more.
>
> >> I appreciate that, but my original comments stand.  There is no valid reason to
> >> state "the regulator circuit needs to get rid of 136W" when the transformer is
> >> not rated to deliver that power.
>
> >You seem to have a poor understand of what the rating of a transformer
> >means.
>
> On the contrary.  A 24V 5A secondary is rated for 120VA.  Your education
> suggests something different?  Please inform us all as to YOUR transformer
> theory.

Yes that is the *rating* in VA and yes that works out to 120/1.5=80W
of power from the rectifier.  It however is far below the limit of
what you can actually get out of the transformer.  It is what the
maker says the transformer can do forever on a normal line voltage and
usually with an air temperature of some 50C.  The transformer does not
contain any significant current limiting.  The output impedance is
fairly low.  The heat sinking on the regulator needs to be designed to
withstand the high line case with a short circuit on the output.  This
is a lot more than the rated power of the transformer.

If the OP goes with less than the amount of heat sinking I suggested,
I predict he will be replacing the transistors very early in the power
supplies life.