Isolated, regulated, toroidal step down transformer AC power supply design. - Page 7

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


.noitasrevnoc a fo wolf lacigol eht wollof ot drah ti sekam ylno gnitsop poT

When you read a book, you start at page one and normally read from the top
left to the bottom right. An author will sell
next person follows on from there, not the answer first then the question.
scattered throughout the rest of the book. That is why top posting is
totally illogical. eg. someone poses a question, the very few books if he
wrote the beginning in chapter 15, then the ending in chapter 2 with the
body of the story spread and




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


LOL, well that is just the epitome of clear communication, Bob.

                    follow your example
I should perhaps

and


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


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    Get back under your bridge, troll.

Ball of Wool


Kitty is just pretending. ..chase it, Kitty, chase it! ..Meow.

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


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I apologise for assuming you had some level of competence and experience
with electronics. I clearly misjudged you initially.

However, what I can tell now after reading these inumerable posts containing
so little information about your alleged "device" and so much sbout yourself
and your opinions is that whether you know it or not, you're a troll. I
don't think your motivations nor intentions in going on this way are to
solve whatever problem you might have, it's to cause conflict and grief.

I doubt whether this "device" actually exists, or whether it's a construct
of experiences and things you've read, as when put together none of it makes
sense and you are unable to come up with a cogent explanation.

In a similar way, I doubt all this business about your family - it's such an
irrelevant thing to bring into a discussion about a technical issue - it
sounds like another fabrication you've made up and thrown in just to cause
conflict and confusion.

I don't quite get what it is you find so attractive about trolling, but I do
regret being sucked in and trying to offer help.






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


What utter piffle.

I won't be bullied into suppling requests for information. It would be an
act of submission to do so and a reward for the bullies.

I will respond to any polite request for more information with the
information requested, provided it is within the terms of the original
question. I do not feel obliged to answer any questions pertaining to
matters outside those terms or conditions, however I am still FREE to answer
them, if I wish.

Bob ASKED me what I did for a job (and quite politely as I remember it) and
I gave him a very short reply. My family commitments are relevant (to the
question of why I have not been able to peruse a number of other possible
avenues of investigation).

Their have been other reasons given. Caution, inexperience and a lack of
equipment being some of them. You must also consider remote location. I
can't just duck around the corner and pick up whatever I may need.

I had a look under the 'bonnet' last night and the regulator ICs are lying
flat on the PCB closely surrounded by many capacitors. The risk of shorting
the pins with the DMM probes is perilous. I need to pick up a set of mini
alligator clips to do the measurements safely. Attaching them when the power
is OFF. At the moment that means waiting until after the Easter break.

I really expect no further help from you, Poxy. And I am untroubled by my
position.

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


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     Get back under your bridge, clueless troll.


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


Does 'Pussy' want some milk?

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


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     Get back under your bridge, troll.


Ball of wool


Kittty is only pretending ...chase it!

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



. . .

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Ok Mark, I have come up with a solution for you.

I have to warn you that it will take some effort, but it is guaranteed
to solve your clipping problem.

You will need to gather the the right tools and parts first:

Anti-static mat and wrist strap.

250W soldering iron.

About 25cm of 2.5mm diameter pure silver wire.

One of Bob's ESR meters (if you are lucky you might still find one at
DSE, otherwise Bob says there is a mob in Canada that supply them).

A large assortment of those Black Gate capacitors - perhaps you have
some left over?

A big sheet of bubble wrap.

This is what you need to do:

I'm sure you have heard that some electronic components are sensitive
to static electricity, so only work on the anti-static mat and ground
yourself with the wrist strap.

Open up the amplifier - sorry, I mean the secret device, and locate
the diodes in the power supply circuitry. You said that the voltage
drop across these can be ignored, but that is just not true - voltage
drop across a diode can be a killer, so those diodes have to go. As
you no doubt know, silver is a very good conductor, so for minimum
voltage drop you need to replace all the diodes with a short length of
the silver wire. You will probably need to drill out the holes in the
PCB a little to do this. Unfortunately, silver is also a good
conductor of heat so this is where you will need the the 250W
soldering iron.

Now I know you have already been through the "recapping" process, but
you have more work to do. With those Black Gate caps being so good, a
few more in there are bound to work wonders, and you can achieve this
by replacing all low value resistors with some of the wonder caps. Of
course, to do this you have to know what value of capacitor is
equivalent to a particular resistor, and this is where Bob's magic
device comes in - you see, it will give you a resistance measurement
for a capacitor! Paradoxically, good capacitors usually have low
equivalent resistance, so you might have to use many capacitors in
series to get the required value, but then that is really good news
because you can cram more of that Black goodness in there.

Once you have done that you can replace the cover and then wrap the
whole thing carefully in bubble wrap and secure it with tape or
string, and then carefully place it in the garbage bin.



Andy Wood
snipped-for-privacy@trap.ozemail.com.au

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


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    I was drinking some coffee while I read that, and I *almost* sprayed
the monitor when I started laughing!
    Very well done Andy - thanks. :-)

Bob




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




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Perhaps Mark could check the variability of his mains supply with this gadget...

http://www.engadget.com/photos/art-lebedevs-vilcus-dactyloadapter/198275 /


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


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gadget...
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     Hehehehe!


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


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Damn! And here I am substituting all those caps with resistors instead!
Especially the big caps, with such a small ESR that they can be replaced simply
with a wire link ...

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


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    Make sure it's silver wire for good acoustic transparency! ;-)



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


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Try again. Hint: he's not calling you "datasheet"

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You aren't cooperating with those who attempt to help.

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That's not a licence to be an asshole.

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maybe you could cal;m down a little and look at it from our perspective

Bye.
   Jasen

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Oh be nice and go to bed Phil.




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



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Not exactly.  There are precious few (if any) three-terminal regulators that
won't handle a 30V or 40V input for 15V out.  Your configuration is far more
likely to suffer from UNDER-voltage out of the rectifier arrangement.

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No, three-terminal regs don't work that way.  Get a datasheet for a 7815 or 7915
and have a good read of the input voltage range.  Let's see, 7815 ...

Dropout voltage (typical): 2.0V
Vin (max): 35V

So a 7815 will regulate as long as the input voltage doesn't exceed 35V or drop
below 17V on the troughs of the input waveform.

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It may be small but it isn't insignificant.  And I don't like your rectification
theory either.

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The Vin-Vout capability of (again, 3-terminal) regs is a spec figure you'll find
on the data sheet, often termed drop-out voltage.  See above.  It's *not* a
percentage thing.  If your input drops (even on transients) to 2V above your 15V
output, or less, you will lose regulation.  20% of 15V is 3V which - if your
rectifier is really providing 18V DC - is barely enough, and ripple at  any sort
of load will kill you.

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I think you mean transformer

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I don't like your rectifier model, but let's ignore that for the moment.

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They should be happier.  Warmer, but happier.  Realise also that the output of
your rectifier system will show significant ripple as load current increases,
and those dips threaten the very regulation those regulators are trying to
provide.

Your concept of how regulators work is more than a worry.  And IMNSHO it
unperpins all your problems.

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Read the data sheet, and understand what a 3-terminal reg does.

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Throwing bulk cap around will obviously improve (aka mask) the regulation
situation.  But it is masking the symptoms, not fixing the cause.

You  mentioned in another post that this is accompanying a move from a 9VAC
wall-wart to a hopefully better transformer.

What I sincerely suggest you do is (in order):

(a)  Get the data sheets for the regulators that you are using.  If they aren't
7815/7915 then I feel compelled to ask why not.

(b)  Measure (even with a DMM) the input voltage to the regulator(s) and
convince yourself that you have enough headroom to operate properly.  Better
still if you check the ripple with a CRO too.  Even better, get a CRO and watch
the waveform applied to the input of the regulators, and load/unload teh system
so that the ripple can be quantified.

(c)  Check whether the regs are running hot to touch.

(d)  Try a 12VAC wall wart, unless the DCin to the regs is already 23V or more.

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Quite frankly, I am astounded that you seemed to think that these problems are
best solved by shooting for an (affordable) transformer offering 1% line
regulation.  If that were the best solution, such transformers would abound, and
Google would have turned up a mutitude of solutions for you.  Rather, the
solution to such requirements have been de rigeur for decades, earning the tag
classical.

Your request was further obfuscated - and the task of steering you towards a
sound and achievable/affordable solution - by giving more of your planned
solution than the description of the application and the problem.

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No, they'd wonder why you were searching for an electronic sledgehammer.

Whether you choose to follow my, or anyone else's, suggestions is up to you.
But among the flaming, you have been given more than enough leads to achieve a
sensible outcome.

And please don't top-post

--

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


Yes I did mean transformer.

Yours is one of the very few contributions to this thread which was
obviously written for my edification, and not for the purpose of an
opportunistic 'free-kick', so to speak.

For that (rather solitary) attitude, I thank you.

P.S. Did you really take exception to this post because I top-posted it?

If not then the problem can't be 'top-posting', per se, right?

If so, then would you also explain what you find intrinsically offensive
about a top-post as opposed to a bottom-post? Plenty of people bottom-post
here but you don't complain.

Isn't it true that it is simply a matter of style, and therefore it is
purely a subjective judgement that you make?

If it is true that you are genuinely aggrieved by my top posting style then,
BECAUSE you have shown me the consideration due to any ordinary person, I
can change it for YOU only.

All other replies remain top posted.

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