doubling output current from 6v ct trans

M

Mat Menzies

Guest
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V to -6V - 0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers separately, put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As soon as I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get a
higher capacity than rated, and why was I getting what appeared to be a
series output when I thought I was setting it up in parrallel?

Mat
 
"Mat Menzies" <mat.nospam@south.com.au> wrote in message
news:3f4dab7b@dnews.tpgi.com.au...
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V to -6V -
0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers separately,
put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As soon as
I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get a
higher capacity than rated, and why was I getting what appeared to be a
series output when I thought I was setting it up in parrallel?
Click to expand...

** The *best* you can do is use only two diodes and one 1000uf cap then
use the centre tap as the common.

This will give you about 6.5 volts DC at 300mA.





............. Phil
 
IF you can get to the wire that goes to the CT terminal, you'll probably
find it is just a loop or turn of the secondary winding taken out to the
tag. cut the loop and thus seperate the secondary into two 3v windings. now
you can parallel these for 3v AC at 600ma. Recify this to DC and take the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v with
fullwave rectification and reasonable filtering.

best of luck -- it's only gonna work if you can seperate the CT into two
windings...

When paralleling up the two secondary windings, the two original outer
terminals should NOT be joined together. You'll know if your paralleling up
didn't work properly as you'll get virtually no output and the transformer
will get stinking hot real quick!

i.e. 1----CT----2 becomes 1-----A (cut) B------2 Join 1 and B
for one terminal, and join A and 2 for the other terminal.


Craig


"Mat Menzies" <mat.nospam@south.com.au> wrote in message
news:3f4dab7b@dnews.tpgi.com.au...
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V to -6V -
0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers separately,
put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As soon as
I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get a
higher capacity than rated, and why was I getting what appeared to be a
series output when I thought I was setting it up in parrallel?

Mat
Click to expand...
 
OK cool, thanks for that Craig.
I'll try and get to the cetre tap winding and see how I go.
It'll be two 6V windings, so I'll easily be able to regulate that to 4.5
VDC. Is there any need to use full rectification when half rectification
will supply a high enough Voltage?
Mat



"Craig Hart" <chart@nospam.ta> wrote in message
news:3f4e16ab$1@usenet.per.paradox.net.au...
IF you can get to the wire that goes to the CT terminal, you'll probably
find it is just a loop or turn of the secondary winding taken out to the
tag. cut the loop and thus seperate the secondary into two 3v windings.
now
you can parallel these for 3v AC at 600ma. Recify this to DC and take the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v with
fullwave rectification and reasonable filtering.

best of luck -- it's only gonna work if you can seperate the CT into two
windings...

When paralleling up the two secondary windings, the two original outer
terminals should NOT be joined together. You'll know if your paralleling
up
didn't work properly as you'll get virtually no output and the transformer
will get stinking hot real quick!

i.e. 1----CT----2 becomes 1-----A (cut) B------2 Join 1 and B
for one terminal, and join A and 2 for the other terminal.


Craig


"Mat Menzies" <mat.nospam@south.com.au> wrote in message
news:3f4dab7b@dnews.tpgi.com.au...
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V to -6V -
0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers separately,
put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As soon
as
I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get a
higher capacity than rated, and why was I getting what appeared to be a
series output when I thought I was setting it up in parrallel?

Mat
Click to expand...
 
"Craig Hart" <chart@nospam.ta> wrote in message
news:3f4e16ab$1@usenet.per.paradox.net.au...
IF you can get to the wire that goes to the CT terminal, you'll probably
find it is just a loop or turn of the secondary winding taken out to the
tag. cut the loop and thus seperate the secondary into two 3v windings.
Click to expand...
He said it was a 6V - 0 - 6V transformer, so that would be two 6V windings.
His two 8.4V outputs prove this is the case.

now
you can parallel these for 3v AC at 600ma. Recify this to DC and take the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v with
fullwave rectification and reasonable filtering.
Click to expand...
Should get about 7V or so at the 500 mA he is after.

best of luck -- it's only gonna work if you can seperate the CT into two
windings...
Click to expand...
Yep. Otherwise he is stuck with 300mA.

When paralleling up the two secondary windings, the two original outer
terminals should NOT be joined together. You'll know if your paralleling
up
didn't work properly as you'll get virtually no output and the transformer
will get stinking hot real quick!

i.e. 1----CT----2 becomes 1-----A (cut) B------2 Join 1 and B
for one terminal, and join A and 2 for the other terminal.


Craig


"Mat Menzies" <mat.nospam@south.com.au> wrote in message
news:3f4dab7b@dnews.tpgi.com.au...
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V to -6V -
0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers separately,
put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As soon
as
I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get a
higher capacity than rated, and why was I getting what appeared to be a
series output when I thought I was setting it up in parrallel?

Mat
Click to expand...
 
"Tony Pearce" <TonyP@hotmail.com> wrote in message
news:3f4ec5c7$0$10354$afc38c87@news.optusnet.com.au...
"Craig Hart" <chart@nospam.ta> wrote in message
news:3f4e16ab$1@usenet.per.paradox.net.au...
IF you can get to the wire that goes to the CT terminal, you'll probably
find it is just a loop or turn of the secondary winding taken out to the
tag. cut the loop and thus seperate the secondary into two 3v windings.

He said it was a 6V - 0 - 6V transformer, so that would be two 6V
windings.
His two 8.4V outputs prove this is the case.

now
you can parallel these for 3v AC at 600ma. Recify this to DC and take
the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v with
fullwave rectification and reasonable filtering.

Should get about 7V or so at the 500 mA he is after.
Click to expand...

** Wrong.

Even if the two 6 volt windings are somehow paralleled and that allows
600 mA AC to be drawn - much less DC can current be drawn. There is a
de-rating factor to be applied, typically 0.62 times the AC current for a
bridge rectifier.

There are also two diode drops - so the expected output will be 6 x
1.41 - 1.8 = 6.66 volts.

600 mA x 0.62 = 372 mA DC.

Small transformers have *very poor* regulation so even these figures
are optimistic and do not allow for the AC supply being a bit low from time
to time




.......... Phil
 
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f4ecc30$0$28117$afc38c87@news.optusnet.com.au...
There are also two diode drops - so the expected output will be 6 x
1.41 - 1.8 = 6.66 volts.
Click to expand...
Two diode drops = 1.8V?

Small transformers have *very poor* regulation
Click to expand...
Yep, which is why he actually gets 8.4V (after diode drops), at low current.

TonyP.
 
lol .. OK
I'll take all this under advisement, chop the centre tap, set the two
windings up in parrallel and ...
"See what happens!" :)
Thats about the best way I can see to find out whats actually gunna happen.
If it all goes droop I'll just put it down to a learning experience, the
purchase of the transformers in the first place was very minimal anyway,
less than 10 bucks for both.



"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f4ecc30$0$28117$afc38c87@news.optusnet.com.au...
"Tony Pearce" <TonyP@hotmail.com> wrote in message
news:3f4ec5c7$0$10354$afc38c87@news.optusnet.com.au...

"Craig Hart" <chart@nospam.ta> wrote in message
news:3f4e16ab$1@usenet.per.paradox.net.au...
IF you can get to the wire that goes to the CT terminal, you'll
probably
find it is just a loop or turn of the secondary winding taken out to
the
tag. cut the loop and thus seperate the secondary into two 3v
windings.

He said it was a 6V - 0 - 6V transformer, so that would be two 6V
windings.
His two 8.4V outputs prove this is the case.

now
you can parallel these for 3v AC at 600ma. Recify this to DC and take
the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v
with
fullwave rectification and reasonable filtering.

Should get about 7V or so at the 500 mA he is after.


** Wrong.

Even if the two 6 volt windings are somehow paralleled and that
allows
600 mA AC to be drawn - much less DC can current be drawn. There is a
de-rating factor to be applied, typically 0.62 times the AC current for a
bridge rectifier.

There are also two diode drops - so the expected output will be 6 x
1.41 - 1.8 = 6.66 volts.

600 mA x 0.62 = 372 mA DC.

Small transformers have *very poor* regulation so even these figures
are optimistic and do not allow for the AC supply being a bit low from
time
to time




......... Phil
Click to expand...
 
oops, sorry, misread the original post...

"Tony Pearce" <TonyP@hotmail.com> wrote in message
news:3f4ec5c7$0$10354$afc38c87@news.optusnet.com.au...
"Craig Hart" <chart@nospam.ta> wrote in message
news:3f4e16ab$1@usenet.per.paradox.net.au...
IF you can get to the wire that goes to the CT terminal, you'll probably
find it is just a loop or turn of the secondary winding taken out to the
tag. cut the loop and thus seperate the secondary into two 3v windings.

He said it was a 6V - 0 - 6V transformer, so that would be two 6V
windings.
His two 8.4V outputs prove this is the case.

now
you can parallel these for 3v AC at 600ma. Recify this to DC and take
the
~1.4x voltage gain to get ~4.2v or so at ~600ma. You might get 4.5v with
fullwave rectification and reasonable filtering.

Should get about 7V or so at the 500 mA he is after.

best of luck -- it's only gonna work if you can seperate the CT into two
windings...

Yep. Otherwise he is stuck with 300mA.


When paralleling up the two secondary windings, the two original outer
terminals should NOT be joined together. You'll know if your paralleling
up
didn't work properly as you'll get virtually no output and the
transformer
will get stinking hot real quick!

i.e. 1----CT----2 becomes 1-----A (cut) B------2 Join 1 and
B
for one terminal, and join A and 2 for the other terminal.


Craig


"Mat Menzies" <mat.nospam@south.com.au> wrote in message
news:3f4dab7b@dnews.tpgi.com.au...
I was after a small 4.5V 500 mA DC plugpack, so I chose a 240V
to -6V -
0 -
+6V 300 mA centre tapped transformer and tried to use the two outputs
in
parrallel.
I firstly used 6 diodes to achieve two parrallel 8.4 VDC outputs, but
unexpectedly got one 17VDC output when they were tied together.
I then removed the dides and used two W04 bridge rectifiers
separately,
put
a 1000uf cap accross each output and I got two 8.4 VDC outputs. As
soon
as
I
tie these two outputs together I get one 17 VDC output.
Is it possible to use the centre tapped winding in parrallel to get
a
higher capacity than rated, and why was I getting what appeared to be
a
series output when I thought I was setting it up in parrallel?

Mat
Click to expand...
 
"Tony Pearce" <TonyP@hotmail.com> wrote in message
news:3f4f0526$0$10355$afc38c87@news.optusnet.com.au...
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f4ecc30$0$28117$afc38c87@news.optusnet.com.au...
There are also two diode drops - so the expected output will be 6 x
1.41 - 1.8 = 6.66 volts.

Two diode drops = 1.8V?

Small transformers have *very poor* regulation

Yep, which is why he actually gets 8.4V (after diode drops), at low
current.
Click to expand...



** I see you are up to your pathetic snipping tricks again - Trevor.



........................ Phil
 
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f4f1438$0$10356$afc38c87@news.optusnet.com.au...
** I see you are up to your pathetic snipping tricks again - Trevor.
Click to expand...
You waste enough bandwidth already Phil, I only snip the irrelevant bits
(although some would say all of your posts are irrelevant :)

TonyP.
 
"Tony Pearce" <TonyP@hotmail.com> wrote in message
news:3f51be53$0$28122$afc38c87@news.optusnet.com.au...
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f4f1438$0$10356$afc38c87@news.optusnet.com.au...

** I see you are up to your pathetic snipping tricks again -
Trevor.

You waste enough bandwidth already Phil,
Click to expand...

** More lies, more snipping, more lies, more snipping ...........



I only snip the irrelevant bits
Click to expand...

** But you are a stinking liar and a poseur and a fuckwit and anonymous.

Did " Trevor " ... the lying turd disappear up his own backside then
re-appear out his own mouth and say ... " hi - I am now Tony Pearce" ?????



The absolute *worst * serial child molesters are complete saints compared
to - Trevor.






................ Phil
 
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f51c57b$0$4187$afc38c87@news.optusnet.com.au...
The absolute *worst * serial child molesters are Phil.
Click to expand...
............. Phil.
 
BEWARE TO ALL :


Some stinking POS calling itself "Tony Pearce" or " Trevor " is
faking messages from me.

Complain to his ISP for illegal posting - have the stinking turd kicked
off usenet.





........... Phil
 
On Sun, 31 Aug 2003 20:10:10 +1000, "Phil Allison"
<philallison@optusnet.com.au> wrote:

Complain to his ISP for illegal posting - have the stinking turd kicked
off usenet.
Click to expand...
We have, bot both you and Rodbot are still here....
 
<David Sauer> wrote in message
news:7hj3lvgcguc2oqcapj919j0a4arvrn3ajo@4ax.com...
On Sun, 31 Aug 2003 20:10:10 +1000, "Phil Allison"
philallison@optusnet.com.au> wrote:

Complain to his ISP for illegal posting - have the stinking turd
kicked
off usenet.

We have, bot both you and Rodbot are still here....
Click to expand...


** Screw you shithead.

Faking another's real identity in order to abuse them is a major
no-no.




.......... Phil
 
On Sun, 31 Aug 2003 20:44:58 +1000, "Phil Allison"
<philallison@optusnet.com.au> wrote:

** Screw you shithead.

Faking another's real identity in order to abuse them is a major
no-no.
Click to expand...
What kind of a shithead would make someone go and do that?
 
<David Sauer> wrote in message
news:cbl3lv0vcmm44a6j2fvqo1ammeni5d2093@4ax.com...
On Sun, 31 Aug 2003 20:44:58 +1000, "Phil Allison"
philallison@optusnet.com.au> wrote:

** Screw you shithead.

Faking another's real identity in order to abuse them is a
major no-no.


What kind of a shithead would make someone go and do that?
Click to expand...


** What kind of stinking arsehole ******assumes***** that such is the
case ??






........ Phil
 
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f51c57b$0$4187$afc38c87@news.optusnet.com.au...
The absolute *worst * serial child molesters are complete saints ...
Click to expand...
*YOUR* words Phil, not mine! So don't write such crap.

TonyP.
 
"Tony Pearce" <Tonyp@optusnet.com.au> wrote in message
news:3f5379ed$0$15134$afc38c87@news.optusnet.com.au...
"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f51c57b$0$4187$afc38c87@news.optusnet.com.au...
The absolute *worst * serial child molesters are complete saints ...

*YOUR* words Phil, not mine! So don't write such crap.

TonyP.
Click to expand...

** Go disappear up your own arse again - Trevor - this time for ever.



......... Phil
 
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