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3 Isolated AC Outputs from 1 AC Source

Hello Everyone,

First let me say thank you for taking your time to read and possibly
respond to my post.

I'm a (very) amatuer electronics designer. Mostly I design things that
I use around the house (The Official term, I believe, is gadgets). My
current need is as follows...

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.

Thank You for your time!
Jeff
 
T

tempus fugit

Jan 1, 1970
0
Hello Everyone,

First let me say thank you for taking your time to read and possibly
respond to my post.

I'm a (very) amatuer electronics designer. Mostly I design things that
I use around the house (The Official term, I believe, is gadgets). My
current need is as follows...

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.

Thank You for your time!
Jeff

I wouldn't normally ask this question, but since by your own admission you
are very amatuer....

Are you sure you need AC power? If this were for DC power, it would be a
much simpler solution. What is the power supply going to be used for?
 
P

Phil Allison

Jan 1, 1970
0
** Groper Alert !!

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.



** Small PCB transformers have poor "regulation" - ie the output voltage
varies with load current by up to 25% from no load to full load.

Only YOU know what the application requires in the way of "equal"
voltage matching.

I suspect that 1:1 transformers rated at 120 volts AC and only a few VA are
hard to find.




....... Phil
 
Thanks for your replies!

exact 1:1 voltage matching is not important.. as long as it's failry
linear, its fine.

If its easier to isolate in DC, thats perfectly acceptable. I can
isolate before DC is turned into AC... So basically, take three
isolated DC Supplies and then convert those to AC...

I do need AC at the end of all this, but since i'm converting 4.5V DC
to 0-90V AC anyway, it's no problem to isolate in the DC Section. I
always thought it was easier to isolate AC Supplies than DC, but if i'm
mistaken, PLEASE do correct me. At the end of the day, I just need
roughly 0-90V DC on three outputs, where current (for the most part)
will not flow between them.

Thanks Again,
Jeff
 
H

Homer J Simpson

Jan 1, 1970
0
My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

Why not? What's it for?






--
 
do need AC at the end of all this, but since i'm converting 4.5V DC
to 0-90V AC anyway, it's no problem to isolate in the DC Section. I
always thought it was easier to isolate AC Supplies than DC, but if i'm

mistaken, PLEASE do correct me. At the end of the day, I just need
roughly 0-90V DC on three outputs, where current (for the most part)
will not flow between them.


Mis Type... I Need roughly 0-90V AC not DC... but I can easily convert
3 DC Feeds to AC - so thats no big deal.

Jeff
 
P

Phil Allison

Jan 1, 1970
0
** Desperate TOP POSTING Groper Alert !!!!

exact 1:1 voltage matching is not important.. as long as it's failry
linear, its fine.


** Uninformative reply.

If its easier to isolate in DC,


** Like hell it is.


I do need AC at the end of all this, but since i'm converting 4.5V DC
to 0-90V AC anyway,


** Err - what is the frequency and what is the wave form like ???

YOU are being far too anal with simple facts.



........ Phil
 
exact 1:1 voltage matching is not important.. as long as it's failryUnimportant.. Was simply stating that it doesn't really matter if
the input voltage is exactly equal to output voltage if a transformer
is used.
** Like hell it is.
I wasn't saying that it is. It was my understanding that it's far
easier to isolate AC, I said that only because another poster said that
it would be "Simple if it were AC"
** Err - what is the frequency and what is the wave form like ???

YOU are being far too anal with simple facts.
32khz Frequency and a nearly square wave-form. Definately not
sine-wave power.

I'm sorry if i'm not providing enough facts, but I'm trying. I will
provide any information necessary if you tell me what I need to tell
you.
 
P

Phil Allison

Jan 1, 1970
0
** Desperate TOP POSTING Groper Alert !!!!

Unimportant.. Was simply stating that it doesn't really matter if
the input voltage is exactly equal to output voltage if a transformer
is used.


** Another uninformative reply.

I wasn't saying that it is.


** I never said YOU said it.

I was warning YOU of bad advice.



32khz Frequency and a nearly square wave-form. Definately not
sine-wave power.


** Christ almighty !!!

YOU should have mentioned ** THAT ** info straight off !!!!

I'm sorry if i'm not providing enough facts, but I'm trying.


** Very.


I will
provide any information necessary if you tell me what I need to tell
you.


** Describe your darn application.

( This will be good ..... )




........ Phil
 
D

D from BC

Jan 1, 1970
0
I speak "newbie" and I'm going to try to translate the following :)
(With reference to the movie Airplane... Old lady says..."I speak
Jive" )

On 11 Jan 2007 19:48:04 -0800, "[email protected]"

[snip]
I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

Translation: I have a controllable AC supply and want to split that up
into 3 isolated outputs.
My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.
Translation: I'm looking for isolation transformers or a 1:1:1:1 that
can handle 90VACrms.
I only need about 20mA on each of the three outputs... 25 MAX.
Translation: I don't want a big honking transformer just something
that has a 20mA to 25mA rating.
So, My two questions...
1. Is this an appropriate solution to my problem?
and
Translation: What are the limitations of an isolation transformer? And
is this the only way?
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.
Translation: How do you search for isolation transformers?
Thank You for your time!
Jeff

One way to best understand the newbie language is to block out
everything you know :)
D from BC
 
H

Homer J Simpson

Jan 1, 1970
0
do need AC at the end of all this, but since i'm converting 4.5V DC
to 0-90V AC anyway, it's no problem to isolate in the DC Section. I
always thought it was easier to isolate AC Supplies than DC, but if i'm

Yes. In fact you cannot isolate DC from DC.

I would look for cheap transformers. Sometimes it is cheaper to convert 110
to 12 and then back to 110 or similar - two cheap transformers may be
cheaper than one specific one.

http://www.allelectronics.com/cgi-bin/item/TX-4025/790500/40_VCT_"#64;_.25_AMPS_TRANSFORMER_.html







--
 
P

Paul E. Schoen

Jan 1, 1970
0
do need AC at the end of all this, but since i'm converting 4.5V DC
to 0-90V AC anyway, it's no problem to isolate in the DC Section. I
always thought it was easier to isolate AC Supplies than DC, but if i'm

mistaken, PLEASE do correct me. At the end of the day, I just need
roughly 0-90V DC on three outputs, where current (for the most part)
will not flow between them.


Mis Type... I Need roughly 0-90V AC not DC... but I can easily convert
3 DC Feeds to AC - so thats no big deal.

Jeff

For 32 kHz you can probably use an audio transformer. Your power
requirement is 90 V at 25 mA or a little over 2 watts. However, at such
high frequency, you might get away with a 400 mW transformer such as Mouser
(Xicon) 42TU019 which is 10K CT to 600 CT. This is about 4:1 ratio. There
is also 42TU012 which is 10K CT to 5K CT, or 1.4:1. They have high winding
resistance of 100 to 600 ohms, so regulation will be poor. 42TU016 is 600
CT to 600 CT with 65 yo 55 ohm windings. It might not saturate at 32 kHz.
Modem transformers are similar, so you might try one out of an old modem.

A power transformer might work at 32 kHz (but not very efficiently). A 6
volt winding at 60 Hz will handle 600 volts at 6 kHz. Probably a few dozen
turns of wire on an iron toroid core would handle 90 VAC at that frequency.
A ferrite core would probably be better. It would be a good learning
exercise to try some of these ideas and see what happens. It's difficult to
provide a perfect solution without knowing exactly what you are trying to
do.

I also don't know why you say it is so easy to convert DC to AC. It is
certainly not as trivial as the reverse.

Paul
 
M

Mike Harrison

Jan 1, 1970
0
** Groper Alert !!





** Small PCB transformers have poor "regulation" - ie the output voltage
varies with load current by up to 25% from no load to full load.

Only YOU know what the application requires in the way of "equal"
voltage matching.

I suspect that 1:1 transformers rated at 120 volts AC and only a few VA are
hard to find.

Not really - using each primary of a dual-primary 230/110v transformer would do it, although
winding-to-winding isolation would be less than normal.
 
Hello Everyone,

First let me say thank you for taking your time to read and possibly
respond to my post.

I'm a (very) amatuer electronics designer. Mostly I design things that
I use around the house (The Official term, I believe, is gadgets). My
current need is as follows...

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.

Thank You for your time!
Jeff
 
P

Phil Allison

Jan 1, 1970
0
"Mike Harrison"
Not really - using each primary of a dual-primary 230/110v transformer
would do it, although
winding-to-winding isolation would be less than normal.


** You have both asserted and contradicted your own utterly fallacious
point in one sentence.

A " dual primary" transformer is NOT a " 1: 1 isolation" transformer.

Especially true in low VA ratings like 2 or 3 VA.

Think - "regulation factor " ......

If you can think at all.....



....... Phil
 
Hello Everyone,

First let me say thank you for taking your time to read and possibly
respond to my post.

I'm a (very) amatuer electronics designer. Mostly I design things that
I use around the house (The Official term, I believe, is gadgets). My
current need is as follows...

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.

The additional information that you want to run at 32kHz is vitally
improtant.

I don't like your chances of buying a suitable transformer with four
identical windings, but you coulld probably wind something suitable on
a decent-sized RM core - the bigger RM cores (like RM-8 and above)
offer formers with a respectable numbr of pins - you'd need at least
eight, more if you started inserting grounded screen between you
windings.

You can buy RM12/I-3C90 half-cores from Farnell (order code305-6855)
and a single section 12-pin former (order code178-513) plus the two
retaining clips/earth tag (order code 433-135) that you need to clamp
the two half cores around the former (after you have wound the coils
onto it) and fix the core assembly to the circuit board.

The details are shown in the RM12/I data sheet at

http://www.ferroxcube.com/prod/assets/rm12i.pdf

which includes a lot of information about cores and formers that you
can't buy in small quantities.

The core that you can buy offers 5.6uH inductance per root turn. One
hundred turns per winding gives you a peak magnetising current of about
16mA, which should be okay.

If you need help in working out the winding details, e-mail me - my
address is real.

If you seriously want identical voltages from all three windings,
widing all four windings with a bundle of four twisted wires - the
unloaded voltages will then be equal to one part in 10^7.

It won't be quite the same as the voltage you apply to the driven
winding, due to the resistive drop as the magnetisng current rises and
falls - to deal with that you'd need a fifth winding through which
you'd drive a magnetising current to give the desired voltage across
one of the four bundled windings.

Hope this helps.
 
P

Phil Allison

Jan 1, 1970
0
I need to 'split' this current source into
I don't like your chances of buying a suitable transformer with four
identical windings,



** What did you just guess the OPs's "completely isolated " meant in
technical terms ?

Do even imagine HE knows ??

Is that wise ????




....... Phil
 
S

Speedskater

Jan 1, 1970
0
Hello Everyone,

First let me say thank you for taking your time to read and possibly
respond to my post.

I'm a (very) amatuer electronics designer. Mostly I design things that
I use around the house (The Official term, I believe, is gadgets). My
current need is as follows...

I have a single power supply creating between 0 and 90V AC (Adjustable
in roughly 1V increments). I need to 'split' this current source into
THREE completely isolated AC Power Sources which are of equal voltage
to the input current (1:1).

My thought is three simple transformers with 1:1 windings. All the
primary sides connected to the 0-90V Supply which would give me 3
isolated 0-90V Secondaries.

I only need about 20mA on each of the three outputs... 25 MAX.

So, My two questions...
1. Is this an appropriate solution to my problem?
and
2. Can anyone reccomend a small transformer (PCB Mount) that could
handle the task? I've searched a bit on Digi-Key and Mouser, but
frankly, I'm not even exactly sure what I'm looking for so its' a bit
hard to find.

Thank You for your time!
Jeff
If size and weight are not issues. but price is. You could get 3 pairs
of transformers. Each rated at 110V input to any voltage output (lets
say 36V AC, for example). Then connect the 36V AC winding of one
transformer to the 36V AC winding of another. So the voltage is 110V
input, 36 V inter-stage, 110V output.
 
P

Phil Allison

Jan 1, 1970
0
"Speedskater"
If size and weight are not issues. but price is. You could get 3 pairs of
transformers. Each rated at 110V input to any voltage output (lets say 36V
AC, for example). Then connect the 36V AC winding of one transformer to
the 36V AC winding of another. So the voltage is 110V input, 36 V
inter-stage, 110V output.


** ROTFL ....

The fuckwit OP now tells us he needs a 32kHz square wave to pass through !!!

Any ordinary 50/60 Hz tranny will need a DAMN BIG dose of salts tor pass
THAT !!





........ Phil
 
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