Isolated, regulated, toroidal step down transformer AC power supply design. - Page 8

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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No.  At the input of a typical 15V regulator you need 17V or 18V as a
minimum, and the maximum will typically be either around 30V-35V, or less
if large load currents are being drawn such that the heat sink of the
regulator gets so hot that the power dissipation of the regulator needs to
be reduced by lowering the input voltage below 30V.

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No, not if the "(nominally) 9 VAC" is actually anywhere near 9VAC, the peak
value of the waveform is sqrt(2) (about 1.4 times) the RMS value, and 9VAC
is conventionally used to refer to 9VRMS, unless otherwise stated.

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It is not small enough to ignore.

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It needs to be well ABOVE the nominal output OR IT WILL NOT WORK.


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If you are using the regulators properly, then they will regulate.  On a bad
day, the output voltage might change by a millivolt or so, and nobody will
notice.  On a good day it will change even less and you will have great
difficulty even measuring the change.

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No, not if it is a regulator.  Maybe you mean "transformer".

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Should work just fine with 19.8V into a 15V regulator.

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Ok, that's why you already have a regulator.  If you are using it properly
then you should not be having any problems.

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All common regulators will accept inputs 40% above the output voltage.  It
is when the input voltage is NOT at least a couple of volts greater than
the output voltage that you will have trouble.
 
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I am not sure that you would make any improvement by changing the
capacitors.  It is possible that you have introduced problems due to the
modifications.  If you would explain what you have done then people would
probably help you, but you indicated that you did not want to do that.

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The problem seems to be that you started out by asserting as facts a few
things that happen not to be correct, and then insulted anyone who tried to
point out your errors.  If you had started out with more humility and less
conviction that you already knew everything on the subject of power
supplies, then you would have received more helpful replies.

I suggest you learn what is inside a voltage regulator and how it works
(from application notes on the National Semiconductor and On Semiconductor
websites if you don't have any suitable books), learn what a half-wave
rectifier and a full-wave bridge rectifier is, learn the relationship
between the peak and RMS voltages of a sine wave, and next time when you're
not sure about something, remember that you won't be attacked for not
knowing something but you will be mocked and insulted viciously if you
pretend to know things that you don't know and persist in asserting with
confidence things that are incorrect rather than listening to correct
(albeit not particularly polite) advice.

Chris



Re: Isolated, regulated, toroidal step down transformer AC power supply design.


No, Chris. That wasn't the problem, although it may 'seem' that way to you.

I did not insult anyone who did not draw first blood. (I can think one
possible exception, but I'll deal with the other 'Bob' later)

One of the reasons why it may 'seem' that way to you is because you may not
be reading the posts in the chronological order they were written. The
structure of the thread can give this illusion, but a more careful
examination of the facts will reveal otherwise.

The policy I adhered to in this newsgroup is precisely the same one I adhere
to in all other human relations. I treat people with exactly the same
respect that they accord to me.

To quote myself  from an a post I made in reply to 'Two Bob' earlier on this
same thread:

"When people ask anything from me, they must display to me the same respect
that I gave to them, when I asked something from them, or I will not submit
to their demands.

If the cost of this personal policy is not receiving the help I requested
then I would much prefer not to receive it. The price of self-respect is
inestimable. Is that too difficult for you to understand?

The direct inference from your comments here and elsewhere on this thread is
that you expect me (and possibly all newcomers) to submit to this bulling in
order to receive the help that they need.

That is the definitive behaviour of a 'Phil-of-pile's."

end quote.

It's there; go read it for yourself.

Secondly, I may well have asserted "as facts a few things that happen not to
be correct". We all harbour some false beliefs, even Phil. However, I
usually qualify statements that I am unsure of with the pre-amble "the way I
understand it". Not in all cases because like most people I understand some
things better than others. There is not the slightest trace of arrogance in
my manner. Indeed that may be the very reason why I have suffered SO MANY
attacks. em.go.

People usually equate a certain level of arrogance in others with knowledge.
If I display no arrogance then I am adjudged to have little knowledge (of
electronics, in this case). A fact that I have repetitively and consciously
confirmed, with simple admissions of that fact.

So the absence of arrogance AND the inability to defend myself with
knowledge is like a beacon to those who like to play the humiliation game.
It says: "soft target here, he can't defend himself, this is a chance to
humiliate someone".

And so it started. Phil dives in and the 'Phil-o-philes' follow suit, safe
in the knowledge that they can strike and not be stuck back.

Phil is nothing more than a common bully and so are the 'Phil-o-philes' that
trail in his wake. The 'Phil-o-phile' is extraordinarily easy creature to
identify. They are the perpetrators of the "me too" humiliations (flaming)
once Phil as identified a target for them to attack. He is the 'decider', as
he often describes himself (that he was describing himself is an inescapable
conclusion , btw.). The one who "gets to decide what others should accept or
believe."

Of course, the 'decider' must also have his first officers, and this too was
implicit in his statement. He ascribed the power to "decide what others
should accept or believe." with the qualities of a RIGHT, that is something
held by some but not others.

He does not describe on what basis he shares this right with others, but it
is a fairly safe assumption that it requires the display of superior
knowledge or experience. Power is, of course, a perfectly negotiable
commodity, so one can envisage any number of arrangements by which he might
share this power out.

You see, the organisation of  'Phil-o-philes' is essentially and elitist
club and membership has its privileges. The main privilege, is the pleasure
drawn from the public humiliation of innocent targets (or even not so
innocent targets, it doesn't really matter) These are his 'attack dogs' so
to speak.

I don't discount the possibility that other members may have their own
motivations for joining his club. Perhaps they actually like Phil but they
are more likely to be scared of him. In some circumstances their decision to
ally themselves with him is purely a practical one, it gets him off their
back and frees up their time to pursue legitimate interests within the
newsgroup. These people are more likely to be the casual observers of the
humiliations rather than his agent provocateurs.

Now, the attitude that many of the casual observers of this all too
predictable event have taken is that in order to receive the help I need, I
must be prepared acquiesce to this bulling, and they have said as much (in
once case EXACTLY that)

I am of the opinion that the price of self-respect is inestimable. If the
cost of my refusal to acquiesce is that I don't receive the help that I need
then I am prepared to pay that cost. I am completely untroubled by my
position.



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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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I think that the reason why people were disagreeing with you and agreeing
with Phil has nothing at all to do with anyone liking Phil.  If I agree
with Phil and not with your understanding of the operation of regulators,
rectifiers and the properties of sine waves, I can assure you that it is
for purely technical reasons.  I did put some technical comments
interspersed within the text of your previous message (quoted above) and
you might find these comments useful, both as technical pointers and as
reasons why people might have gained the impression that you were asking
the wrong question in your original post.

Chris






Re: Isolated, regulated, toroidal step down transformer AC power supply design.


I think I already answered it Bob. Twice, in fact.

What is your obsession with people repeating things. Over and over and over.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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    You haven't clearly answered anything.
    What I can't understand is why people (even Phil) are continuing to
try to give you useful advice despite your arrogant smug delusional
attitude and total absense of knowledge of what you're babbling about.
    What a waste of bandwidth.







Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Do I need to draw a picture for you Bob?

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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Why do you need to regulate the input voltage to the regulator?
It is the function of the regulator to accept an unregulated input and provide a
stable, regulated output.

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Just read why. Its in the thread.

Some have disputed the explanation. Others have agreed with it (with
qualifications).

I can't just keep repeating myself. Sorry.

I've already given the explanation about half a dozen times. Read the
thread.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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No it isn't. You simply spout a whole lot of hogwash in your thread.

Are you some kind of UFO spotter with tinfoil earplugs?

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Yes it is.

Because I believed the voltage of the AC domestic supply was straying
outside the operating range of the existing regs (after transformation and
voltage doubling rectification) and because I wanted to replace an existing
wall-wart AC power supply with a regulated AC power supply and because the
application displays errant behaviour during times of over voltage supply.

Whatever criticisms you can make of my reasons, they are there in the thread
about 10 times. You didn't read the thread.

If I wished to spot UFO's, I don't think I'd need earplugs, of any
description.



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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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Once again, your assumptions appear incorrect. The AC mains moves around a bit,
usually to within +/-10%. Manufacturers know this and product is designed to
handle it.

You have a little 9VAC wall wart transformer and these small transformers
usually have poor load regulation so its output when lightly loaded is probably
around 15VAC.

You don't have a voltage doubler, you have a pair of half-wave rectifiers which
give you a bipolar DC supply which is unregulated. The unregulated DC supply is
a good place to put those super caps, so as to smooth out the ripple in the
supply to the regulators.

The regulators will accept a minimum of around +/-17VDC to regulate properly.
With your wall wart, you probably have about 20VDC on their inputs so it works
OK, until you load it down a bit. Then the wall wart AC output will drop and the
inputs to the regulators will drop below 17V. Now your regulators will not be
able to regulate. Your mystery circuit may not like this very much.

If you replace your wall wart with a better 9VAC transformer then your
regulators may have an input below 17VDC most of the time and fail to regulate.
You should probably replace the wall wart with a 12-15VAC transformer with good
load regulation specs. Then your regulators will be happy with their input
voltage and regulate all the time.

However, you must be aware that linear regulators get hot if they have a large
voltage drop across them when under load, so you may need to make sure they are
mounted to a heatsink to dissipate this heat.

All of this has been spelt out to you many times here by many people. Is there
anything here you don't follow?

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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I think you'll find that you've offended Mark in many, many ways. What you
think is logical, sensible advice based on the operating principles of the
components involved is in fact a bitter, unjustified attack on him.

He's TOLD you what you need to know to help him, so stop crapping on about
irrelvant thigs like "voltages" and "drop outs" and "specifications" and
so-called "facts" and start agreeing that he's clearly suffering from a bad
pair (!) of regulators and the one dual-rail power supply design in the
world that only functions correctly with an insanely complex thing that
generates regulated AC.




Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Whatever Poxy, I really don't give a hoot.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Some of my assumptions may well have been incorrect, but they are ALL THERE
in the thread and that was ALL I claimed about them.

..but you retorted "No it isn't. You simply spout a whole lot of hogwash in
your thread."

So you can probably understand my frustration (about being asked to repeat
things over and over again) and my futher presumptions that:

a) You didn't read (or understand) the thread. You got it wrong.

b) Having not read (or understood) the thread, decided that I was
"spout[ing] a whole lot of hogwash in [my] thread."

So, you came to a conclusion on a wrong basis. I.E. Having not read or
understood the thread.

I HAVE read the thread. ALL of it. And I know that you have made little
contibution to what has already been written.

Yes, it is a pair of half-wave rectifiers which DOUBLE the voltage. 9 VAC in
and +/-15 VDC out AFTER regulation. Before regulation it MUST be something
less than 18 VDC, but the schematic does not specify this. The diodes look
like Schottkys to me, I haven't replaced them.

I would say that these simple features (9 VAC in, 15 VAC out, after
regulation) qualify the rectifier as a "voltage DOUBLING design". It is in
the SCHEMATIC and I can reproduce it.

I am calling your BLUFF. It is a "voltage DOUBLING design".

Wolf in a sheep's clothing.


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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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No, it must be more than that or the regulators won't regulate. Once again, you
have no idea what you are talking about.

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No it isn't. You don't have a clue. You've said so previously. It's a pair of
half wave rectifiers, one for the +DC rail and one for the -DC rail.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


9 VAC in, 15 VDC out, after regulation.

How is that NOT a voltage DOUBLING design?

Or is it because you believe that such a design is impossible?

It must be one or the other.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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That's not what you have got. It's what you think you have got.
You have 30VDC out (+/-15VDC).

You have a wall wart transformer with poor load regulation. I'm guessing it's
about 15VAC you have coming out of your wall wart. I also suspect the original
design is relying on this to work.

Try taking some measurements rather than quoting the info that's printed on it.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.



"swanny"
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** Nope.

From the copious schizoid ramblings of this delusional bush maggot  -  I now
surmise the PSU he has operates from a nominal 9 volt AC plug pack with a
couple of amps capacity.  One side of the secondary goes directly to circuit
ground.

Then come four diodes and four electros ( values not described) that act
together as " charge pump" voltage multipliers. This will generate maybe
+/- 23 volts DC ( plus ample ripple) at the input to the 7815 / 7915 regs.

Load regulation will be mediocre  -  at best.

What he ought to do is get a new AC supply tranny ( toroidal is OK) with a
18-0-18 volt secondary of circa 2.5 amps and use a bridge rectifier and
filter electros of say 6,800 uF or a parallel combo to that same sort of
value.

This will have good load regulation and low ripple.

But you will never tell  HIM  that   !!



......   Phil

 



Re: Mark Ilsley = UTTER FUCKWIT LIAR
Meeeeow! I can just picture you, sitting in Pilthy's lap.

Will you chase a ball of wool for him as well?


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Re: Mark Ilsley = UTTER FUCKWIT LIAR
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Troll (Internet)
 From Wikipedia, the free encyclopedia

"In Internet terminology, a troll is someone who intentionally posts
derogatory or otherwise inflammatory messages about sensitive topics in
an established online community such as an online discussion forum to
bait users into responding."



   Get back under your bridge, troll.

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