Calculating DC Output Current From Unregulated AC Transforme

[John Larkin]

On Sun, 13 Jul 2008 00:59:42 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

emailaddress@insightbb.com


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.





..... Phil

Having an unusually bad day, Phil? You see ever so slightly more
crazed than normal.

John

 

On Jul 11, 4:07 pm, mrdarr...@gmail.com wrote:

On Jul 9, 6:39 pm, emailaddr...@insightbb.com wrote:





On Jul 9, 9:26 pm, emailaddr...@insightbb.com wrote:

I have an application in which I need to determine if a transformer is
suitable.
Perhaps a little more info about the project is in order.  Following
the transformer there'll be a bridge rectifier, smoothing cap... then
a linear regulator suppling constant current to charge batteries.  The
circuit is a bit more involved than only this (protection diodes,
charge controller, etc) but this is the subsection in question and the
rectified output of the transformer will need to stay above roughly
12.3VDC so I'm trying to figure out what constant current this
transformer (or others) can supply.

Another thing I am wondering is if a basic, typical small brick AC-DC
switching supply is stable powering this kind of load.  Stripping down
the circuit to the basic topology, what if it had for example:

AC-DC SMPS -> LM317 -> 1.25 Ohm resistor (LM317 in current regulating
config) -> 1A into Battery Pack + LM317 feedback

Since the SMPS is trying to regulate to it's spec'd voltage, let's say
that is 13V even if an uncommon value, will it run stable doing so and
if so, is that at the same constant output wattage from the SMPS the
whole time, with the linear regulator simply dropping more voltage,
creating more heat at the beginning of a battery recharge cycle since
it's suppling constant current to batteries that are at a lower
initial, low state-of-charge voltage?

Why so many LM317s?  They will generate heat too, and waste energy.

First, the example is not something I intend to build at all, it is
just providing an example, a load.

Second, in the example there is only one LM317, when I mentioned
"LM317" the 2nd and third time I was only describing the typical
topology of using one LM317 in the context of it being in current
limiting mode. I used an example that is straight from National's
LM317 datasheet since many would presumably be familiar with it.

What are you charging?  What supply voltage do you need?

I am not building that example. The first example or something fairly
similar I did build a few years ago but now I have no need to consider
the charging or other aspects of the circuit beyond the supply to it,
because it used to be a stationary charger with capability of charging
several different sized packs but it has been reused now for a single
set of packs all with 6 cells. Therefore the most desirable supply
has changed from what it used formerly to something more closely
matched. However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.

 

On Jul 11, 4:37 pm, John Fields <jfie...@austininstruments.com> wrote:

On Wed, 9 Jul 2008 18:26:12 -0700 (PDT), emailaddr...@insightbb.com
wrote:





I have an application in which I need to determine if a transformer is
suitable.

Transformer is rated for 12VAC, 1.67A but I need DC.  I could put a
bridge rectifier and capacitor after it easily enough but how does one
go about calculating the DC output this is capable of?

I've previously used a x 1.41 factor to convert which would give
16.92V, minus the forward drop of a couple silicon diodes in the
bridge rectifier estimated at roughly ( 2 * 0.7V, ignoring changes in
diode forward drop at different current) which would leave (16.92 -
1.4) = 15.5V, but am I correct in thinking this is peak DC output and
there is a different calculation needed to arrive at the output
voltage if the load were drawing 1.67A?

Perhaps a little more info about the project is in order.  Following
the transformer there'll be a bridge rectifier, smoothing cap... then
a linear regulator suppling constant current to charge batteries.  

Why can't you just used the raw unfiltered DC and current limit the
input to the battery?

I am not designing a charging circuit. The charging circuit is fixed,
done years ago, works fine. It's just being mated with a different
supply because the need for it has changed. I am looking for an
equation to qualify transformers per their AC spec for DC supply when
used with a basic bridge rectifier following them.

 

On Jul 11, 2:34 pm, ehsjr
<e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:

I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear.  There is no single formula for you.  Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved.  You insist on ignoring them.  So, we can't
help you, no matter how hard we try.  Sorry.

A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation.

There is an equation that could be made. How accurate the answer from
it would depend on how complete it was. I came here looking to make
as complete an equation as possible but it seems everyone else is
apathetic about the idea and only wants to tell me I don't "need" to
know or that it can't be done.

It's not magic. A caveman looking at a bic lighter would think that
is magic but is it? Your great great grandfather, if he were alive
today, might think a computer is magic, but is it? Just because
someone doesn't know something it doesn't become magic. It would just
require someone bothering to do so, which I was attempting but it
seems I'm going it alone because others think it's too hard or they're
too lazy or whatever the reason. That's fine, nobody is compelled to
do anything but if they had no assistance (some replying did!) then as
always they should've just moved on to the next thread.

 

On Jul 12, 10:50 am, "Phil Allison" <philalli...@tpg.com.au> wrote:

emailaddr...@insightbb.com

Why can't you just used the raw unfiltered DC and current limit the
input to the battery?

I am not designing a charging circuit.

** You are NOT designing  ANYTHING  AT ALL

YOU   STINKING  CRIMINAL  LIAR  !!!!!!!!!!

 FOAD  -  you anonymous pile of shit.

.....  Phil

LOL

Careful now, you might blow a gasket.

 

[John Fields]

On Sat, 12 Jul 2008 07:40:45 -0700 (PDT), emailaddress@insightbb.com
wrote:

I am not building that example. The first example or something fairly
similar I did build a few years ago but now I have no need to consider
the charging or other aspects of the circuit beyond the supply to it,
because it used to be a stationary charger with capability of charging
several different sized packs but it has been reused now for a single
set of packs all with 6 cells. Therefore the most desirable supply
has changed from what it used formerly to something more closely
matched. However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.

---
Yes, but what you're asking for is a transformer design panacea, and
there is none.

Just consider the almost infinite combination of lamination
geometries, core area and length, copper losses, core losses, wire
sizes, winding window areas, and on and on and you may start to
appreciate that a can of worms you're opening up.

For your purposes (after all, for goodness' sake it's only a battery
charger) this is probably good enough:

http://www.mcitransformer.com/i_notes.html

If it isn't, I recommend William M. Flanagan's: "Handbook of
Transformer Design and Applications", ISBN 0-07-021291-0.

http://www.amazon.com/gp/product/0070212910

JF

 

[John Fields]

On Sat, 12 Jul 2008 07:56:53 -0700 (PDT), emailaddress@insightbb.com
wrote:

On Jul 11, 2:34 pm, ehsjr
e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:

I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear.  There is no single formula for you.  Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved.  You insist on ignoring them.  So, we can't
help you, no matter how hard we try.  Sorry.

A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation.

There is an equation that could be made. How accurate the answer from
it would depend on how complete it was.

---
Funny, meteorologists feel the same way, and yet it seems that
detecting that last elusive flap of butterfly wings has been
perpetually beyond their grasp.

JF

 

[John Larkin]

On Sun, 13 Jul 2008 01:02:47 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

emailaddress@insightbb.com


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.




..... Phil

http://www.sfgate.com/cgi-bin/object/article?o=6&f=/c/a/2008/07/12/DDCOMICS12.DTL

John

 

[Baron]

John Larkin wrote:

On Sun, 13 Jul 2008 01:02:47 +1000, "Phil Allison"
philallison@tpg.com.au> wrote:


emailaddress@insightbb.com


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.




..... Phil





http://www.sfgate.com/cgi-bin/object/article?o=6&f=/c/a/2008/07/12/DDCOMICS12.DTL

John

LOL. Nice ! Thats a keeper.

--
Best Regards:
Baron.

 

On Jul 12, 7:40 am, emailaddr...@insightbb.com wrote:
...snip..

However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.

Universal equation. Here you go.

http://en.wikipedia.org/wiki/Heat_equation
http://en.wikipedia.org/wiki/Newton%27s_law_of_cooling#Newton.27s_law_of_cooling

Also check out "Introduction to Heat Transfer" by Incropera and
DeWitt.

The game is to keep the transformer wires at only a moderate
temperature higher than ambient, or you will melt the wiring
insulation.

Knock yourself out.

Michael

 

[ehsjr]

John Fields wrote:

On Sat, 12 Jul 2008 07:56:53 -0700 (PDT), emailaddress@insightbb.com
wrote:


On Jul 11, 2:34 pm, ehsjr
e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:


I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear. There is no single formula for you. Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved. You insist on ignoring them. So, we can't
help you, no matter how hard we try. Sorry.

A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation.

There is an equation that could be made. How accurate the answer from
it would depend on how complete it was.


---
Funny, meteorologists feel the same way, and yet it seems that
detecting that last elusive flap of butterfly wings has been
perpetually beyond their grasp.

JF

Nice analogy, wonder if he'll get it.

What is interesting to me is the apparent contradiction in
the op's thinking. He chooses to lecture respondents with
his thinking, rather than attempt to understand what they
are saying. Or, if not lecture, argue with points that are
made. I've seen this a few times here - someone comes here,
states that they don't know about X, and asks a question.
But then they argue with the answer! What kind of thinking
is that? Is it the "new way of thinking" or ???

Ed

 

[Jamie]

emailaddress@insightbb.com wrote:

On Jul 11, 4:07 pm, mrdarr...@gmail.com wrote:

On Jul 9, 6:39 pm, emailaddr...@insightbb.com wrote:






On Jul 9, 9:26 pm, emailaddr...@insightbb.com wrote:

I have an application in which I need to determine if a transformer is
suitable.
Perhaps a little more info about the project is in order. Following
the transformer there'll be a bridge rectifier, smoothing cap... then
a linear regulator suppling constant current to charge batteries. The
circuit is a bit more involved than only this (protection diodes,
charge controller, etc) but this is the subsection in question and the
rectified output of the transformer will need to stay above roughly
12.3VDC so I'm trying to figure out what constant current this
transformer (or others) can supply.

Another thing I am wondering is if a basic, typical small brick AC-DC
switching supply is stable powering this kind of load. Stripping down
the circuit to the basic topology, what if it had for example:

AC-DC SMPS -> LM317 -> 1.25 Ohm resistor (LM317 in current regulating
config) -> 1A into Battery Pack + LM317 feedback

Since the SMPS is trying to regulate to it's spec'd voltage, let's say
that is 13V even if an uncommon value, will it run stable doing so and
if so, is that at the same constant output wattage from the SMPS the
whole time, with the linear regulator simply dropping more voltage,
creating more heat at the beginning of a battery recharge cycle since
it's suppling constant current to batteries that are at a lower
initial, low state-of-charge voltage?

Why so many LM317s? They will generate heat too, and waste energy.


First, the example is not something I intend to build at all, it is
just providing an example, a load.

Second, in the example there is only one LM317, when I mentioned
"LM317" the 2nd and third time I was only describing the typical
topology of using one LM317 in the context of it being in current
limiting mode. I used an example that is straight from National's
LM317 datasheet since many would presumably be familiar with it.


What are you charging? What supply voltage do you need?



I am not building that example. The first example or something fairly
similar I did build a few years ago but now I have no need to consider
the charging or other aspects of the circuit beyond the supply to it,
because it used to be a stationary charger with capability of charging
several different sized packs but it has been reused now for a single
set of packs all with 6 cells. Therefore the most desirable supply
has changed from what it used formerly to something more closely
matched. However, it is fairly beside the point that I am looking for
a universal equation that ignores all of this. Many people seem to be
saying the rest matters and yes of course it does - but it is still
theoretically expressable in an equation with the factors that change
as variables.

if it has any meaning at all for the subject..

If you're working with an existing xformer for example. What I have
done when not having all the spec's for the xformer was to measure the
primary and secondary DC resistance of the xformer. the primary side
can be scaled by the reference of the ratio of the transformer..

For example, lets assume you have 120 volt service into a wallwart,
the unit outputs 12 volts, this would be a 10:1 ratio. So if we were to
measure lets say 200 ohms on the primary side, we would thus scale that
down by 10 = 20 ohms. The DC resistance on the secondary side is simply
added to this to give you a sum R..
You can look at this as an imaginary resistor in the xformer..

Not knowing the factors of the xformer makes efficiency unknown here,
we can only guess an average and we shouldn't assume it to be near 1.0

I would say 0.8 to be safe.

When calculating the voltage output, you use the R in series
with the load to help determine the voltage drop on the output.
Of course, with a full bride you must also consider the .7 or 1.3
voltage lost depending on what type you use.

A 2 diode full wave rectifier works the best how ever, you'd need the
proper output on the xformer for this..

THen there is the ripple voltage at the filter caps which gets
influenced from the R in the xformer..

In many cheap designs, this R in the xformer is actually used as part
of the filtering to help give a more stable voltage at lower current
demand, the same as putting in a real resistor in series to the caps for
the same reason.

That's about as basic I can describe it.
http://webpages.charter.net/jamie_5"

 

[John Fields]

On Sat, 12 Jul 2008 22:00:45 GMT, ehsjr
<e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote:

John Fields wrote:
On Sat, 12 Jul 2008 07:56:53 -0700 (PDT), emailaddress@insightbb.com
wrote:


On Jul 11, 2:34 pm, ehsjr
e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:


I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear. There is no single formula for you. Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved. You insist on ignoring them. So, we can't
help you, no matter how hard we try. Sorry.

A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation.

There is an equation that could be made. How accurate the answer from
it would depend on how complete it was.


---
Funny, meteorologists feel the same way, and yet it seems that
detecting that last elusive flap of butterfly wings has been
perpetually beyond their grasp.

JF

Nice analogy, wonder if he'll get it.

What is interesting to me is the apparent contradiction in
the op's thinking. He chooses to lecture respondents with
his thinking, rather than attempt to understand what they
are saying. Or, if not lecture, argue with points that are
made. I've seen this a few times here - someone comes here,
states that they don't know about X, and asks a question.
But then they argue with the answer! What kind of thinking
is that? Is it the "new way of thinking" or ???

---
I've seen it a few times also, and I think it's a way of trying to
save face by not admitting that the gift that was given incurred
emotional indebtedness.

That is, if you give me a gift of knowledge and I dis it, I'll still
have the gift but in my mind I won't owe you anything for it.

Make sense?

JF

 

[John Fields]

On Sun, 13 Jul 2008 12:21:58 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

"John Fields"

I've seen it a few times also, and I think it's a way of trying to
save face by not admitting that the gift that was given incurred
emotional indebtedness.

That is, if you give me a gift of knowledge and I dis it, I'll still
have the gift but in my mind I won't owe you anything for it.

Make sense?


** If you imagine some little a brat throwing a toy that is not the one he
wanted back at Santa.

---

Yeah, good one.

JF

 

[default]

On Sun, 13 Jul 2008 01:02:47 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

emailaddress@insightbb.com


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.

Can't you just feel the love?

--


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http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
---= - Total Privacy via Encryption =---

 

[Michael A. Terrell]

default wrote:

On Sun, 13 Jul 2008 01:02:47 +1000, "Phil Allison"
philallison@tpg.com.au> wrote:


emailaddress@insightbb.com


I am not designing a charging circuit.


** You are NOT designing ANYTHING AT ALL

YOU STINKING CRIMINAL LIAR !!!!!!!!!!


FOAD - you anonymous pile of shit.

Can't you just feel the love?

Phil must be out of toasters to molest.


--
http://improve-usenet.org/index.html

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm

Sporadic E is the Earth's aluminum foil beanie for the 'global warming'
sheep.

 

[John Fields]

On Sat, 12 Jul 2008 07:44:00 -0700 (PDT), emailaddress@insightbb.com
wrote:

On Jul 11, 4:37 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 9 Jul 2008 18:26:12 -0700 (PDT), emailaddr...@insightbb.com
wrote:





I have an application in which I need to determine if a transformer is
suitable.

Transformer is rated for 12VAC, 1.67A but I need DC.  I could put a
bridge rectifier and capacitor after it easily enough but how does one
go about calculating the DC output this is capable of?

I've previously used a x 1.41 factor to convert which would give
16.92V, minus the forward drop of a couple silicon diodes in the
bridge rectifier estimated at roughly ( 2 * 0.7V, ignoring changes in
diode forward drop at different current) which would leave (16.92 -
1.4) = 15.5V, but am I correct in thinking this is peak DC output and
there is a different calculation needed to arrive at the output
voltage if the load were drawing 1.67A?

Perhaps a little more info about the project is in order.  Following
the transformer there'll be a bridge rectifier, smoothing cap... then
a linear regulator suppling constant current to charge batteries.  

Why can't you just used the raw unfiltered DC and current limit the
input to the battery?


I am not designing a charging circuit. The charging circuit is fixed,
done years ago, works fine. It's just being mated with a different
supply because the need for it has changed. I am looking for an
equation to qualify transformers per their AC spec for DC supply when
used with a basic bridge rectifier following them.

---
Use Irms = 2.0 Idc and you'll always be safe .

JF

 

[ehsjr]

John Fields wrote:

On Sat, 12 Jul 2008 22:00:45 GMT, ehsjr
e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote:


John Fields wrote:

On Sat, 12 Jul 2008 07:56:53 -0700 (PDT), emailaddress@insightbb.com
wrote:



On Jul 11, 2:34 pm, ehsjr
e.h.s.j.r.removethespampunctuat...@bellatlantic.net> wrote:



I don't want to argue - that seems your intent.
I know you want a magic formula - you have made that
clear. There is no single formula for you. Those who
have replied have made that clear.

We've tried to show you some of the factors that are
involved. You insist on ignoring them. So, we can't
help you, no matter how hard we try. Sorry.

A formula yes, but no it's not magic. It simply requires considering
all the significant variables which I'd hoped others would assist
with, but obviously nobody else wants to do more than argue instead of
putting thought into what such an equation would look like. If you
say "it depends", then that should be in an equation. If you say some
other thing depends too, then that too can be put into the equation.

There is an equation that could be made. How accurate the answer from
it would depend on how complete it was.


---
Funny, meteorologists feel the same way, and yet it seems that
detecting that last elusive flap of butterfly wings has been
perpetually beyond their grasp.

JF

Nice analogy, wonder if he'll get it.

What is interesting to me is the apparent contradiction in
the op's thinking. He chooses to lecture respondents with
his thinking, rather than attempt to understand what they
are saying. Or, if not lecture, argue with points that are
made. I've seen this a few times here - someone comes here,
states that they don't know about X, and asks a question.
But then they argue with the answer! What kind of thinking
is that? Is it the "new way of thinking" or ???


---
I've seen it a few times also, and I think it's a way of trying to
save face by not admitting that the gift that was given incurred
emotional indebtedness.

That is, if you give me a gift of knowledge and I dis it, I'll still
have the gift but in my mind I won't owe you anything for it.

Make sense?

JF

Ah. Thanks.

Ed

 

[ehsjr]

Phil Allison wrote:

"John Fields"


I've seen it a few times also, and I think it's a way of trying to
save face by not admitting that the gift that was given incurred
emotional indebtedness.

That is, if you give me a gift of knowledge and I dis it, I'll still
have the gift but in my mind I won't owe you anything for it.

Make sense?



** If you imagine some little a brat throwing a toy that is not the one he
wanted back at Santa.



..... Phil

Thanks! That example makes the concept clear.

Ed

 

[John Fields]

On Wed, 16 Jul 2008 02:55:03 -0700 (PDT), emailaddress@insightbb.com
wrote:

I'm sorry if I did not clarify this, but I do not need an introductory
course in sizing transformers. The whole point was moving beyond the
generic overestimates towards the real science in what is actually
necessary. I lecture towards the end of saying, ok, but this is
common knowlege, what else do you know? Maybe it takes a village,
maybe no one person has the entire answer but it seems to get there we
need to have some lecture, some dispelling of comfort zones and get
right down to the actual criteria necessary and have that proven
through real worl examples of success or failure, not just saying "use
a bigger hammer", until it is proven to be needed.

Yes, I will argue with an answer when I ask for an equation and
someone tells me otherwise. I have built plenty of PSU over the
years, if I needed to know what I have already done successfully then
I would have asked a different question? No offense intended, but you
need to focus on what I asked, as do others. If they are ignorant of
the answer, there is no need to reply.

---
You may have _built_ plenty of PSU over the years, but from your
question re. transformer sizing it appears that all you were doing was
grunt work, putting together someone else's design, with no real
insight as to the "why" of the transformer's capacity needing to be
larger than what was required to drive the load.

Instead of being an annoying little ass you might try thanking those
of us who have given you good advice instead of pretending that,
somehow, we did you a disservice.

Oh, and by the way, Fuck you.

JF