hamfistedly constructing a psu without killing myself...

[bengo]

hi

maybe someone could help me?

i've got to make a power supply for an old synth, that needs:

200mA at -9v 0v 9v and 18v.

i was hoping i could do it as a botch job, by connecting three 9v
adaptors together in series, but i just can't see how i could make the
-9v and stop it being 0, 9, 18, and 27.

how about if i stuck an off the shelf voltage regulator on the lead
i'll take off between the second and third 9v power adaptor, and set
that to 9v, will that force the rest of the outputs into line?

i'm really keen not to have to break out the calculator and soldering
iron to build a string of voltage regulator zener diode circuits
because i'm really busyat the moment. i'm also keen not to wire up the
0v line to the earth as i suspect that will keep tripping the fuse,
introduce extra noise, and possibly also kill me. maybe i'm just
paranoid.

any help gratefully received, email or here...

bengo

 

[happyhobit]

bengo <bigben@dsl.pipex.com> wrote:

hi

maybe someone could help me?

i've got to make a power supply for an old synth, that needs:

200mA at -9v 0v 9v and 18v.

i was hoping i could do it as a botch job, by connecting three 9v
adaptors together in series, but i just can't see how i could make the
-9v and stop it being 0, 9, 18, and 27.

Use your 3 power supplies, just make the 9 volt point ground. Then ground
becomes –9 volts, the old +18 is now +9 and the old +27 is now +18.

--
Jay
--------------------------------------------------------------------
"I'm pullin' for you; we're all in this together", Red Green
--------------------------------------------------------------------

 

[tempus fugit]

Does the old synth use an adaptor? If not, I think you'll find that a wall
wart gives unpredictable and unregulated outputs.
You could use the other poster's setup, but I think I would be using
requlators in there too.

"bengo" <bigben@dsl.pipex.com> wrote in message
news:b7901337.0404011109.54c79c85@posting.google.com...

hi

maybe someone could help me?

i've got to make a power supply for an old synth, that needs:

200mA at -9v 0v 9v and 18v.

i was hoping i could do it as a botch job, by connecting three 9v
adaptors together in series, but i just can't see how i could make the
-9v and stop it being 0, 9, 18, and 27.

how about if i stuck an off the shelf voltage regulator on the lead
i'll take off between the second and third 9v power adaptor, and set
that to 9v, will that force the rest of the outputs into line?

i'm really keen not to have to break out the calculator and soldering
iron to build a string of voltage regulator zener diode circuits
because i'm really busyat the moment. i'm also keen not to wire up the
0v line to the earth as i suspect that will keep tripping the fuse,
introduce extra noise, and possibly also kill me. maybe i'm just
paranoid.

any help gratefully received, email or here...

bengo

 

[bengo]

hi

i can buy regulated power supplies and check them with a multimeter,
if it doesnt work i've just splashed money on adaptors i can use
anyway.

but is it really ok to stick them in series to get -9v? i know i'm
maybe being foolish, and they'll kind of make -9v 0v 9v and 18v
relative to each other, but i just don't see how they won't make 0v 9v
18v and 27v....

sigh, i used to be clever...

b


"tempus fugit" <toccata@no.spam.ciaccess.com> wrote in message news:<W15bc.53$Vp6.43@nntp-post.primus.ca>...

Does the old synth use an adaptor? If not, I think you'll find that a wall
wart gives unpredictable and unregulated outputs.
You could use the other poster's setup, but I think I would be using
requlators in there too.

"bengo" <bigben@dsl.pipex.com> wrote in message
news:b7901337.0404011109.54c79c85@posting.google.com...
hi

maybe someone could help me?

i've got to make a power supply for an old synth, that needs:

200mA at -9v 0v 9v and 18v.

i was hoping i could do it as a botch job, by connecting three 9v
adaptors together in series, but i just can't see how i could make the
-9v and stop it being 0, 9, 18, and 27.

how about if i stuck an off the shelf voltage regulator on the lead
i'll take off between the second and third 9v power adaptor, and set
that to 9v, will that force the rest of the outputs into line?

i'm really keen not to have to break out the calculator and soldering
iron to build a string of voltage regulator zener diode circuits
because i'm really busyat the moment. i'm also keen not to wire up the
0v line to the earth as i suspect that will keep tripping the fuse,
introduce extra noise, and possibly also kill me. maybe i'm just
paranoid.

any help gratefully received, email or here...

bengo

 

[Bob Masta]

On 2 Apr 2004 20:38:53 -0800, bigben@dsl.pipex.com (bengo) wrote:

hi

i can buy regulated power supplies and check them with a multimeter,
if it doesnt work i've just splashed money on adaptors i can use
anyway.

but is it really ok to stick them in series to get -9v? i know i'm
maybe being foolish, and they'll kind of make -9v 0v 9v and 18v
relative to each other, but i just don't see how they won't make 0v 9v
18v and 27v....

The power supplies don't know what you are using as a
ground reference. Assuming each supply is the usual
transformer-isolated type, then you can make any
junction the ground: You can ground the top of
the chain and call the outputs 0, -9, -18, and -27,
or ground the top of the middle for +9, 0, -9, -18,
or whatever you want... everything is relative to
the point you choose as ground.

However, depending on the circuit you are
running, this chain may not be the best way
to operate. That's because the current for
one output must pass through two or more
supplies, so you not only may not get the
current capability you think, but you may
get added ripple, plus modulation of the
high voltage part of the circuit by loads in
the low voltage part. And any current
limiting or other protection will be messed
up as well.

But if you have the supplies or they
are cheap enough, you can always
try your daisly chain and see what happens!






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[bengo]

any suggestions about what current the adaptors should be?

b



NoSpam@daqarta.com (Bob Masta) wrote in message news:<406ebeb8.2460744@news.itd.umich.edu>...

On 2 Apr 2004 20:38:53 -0800, bigben@dsl.pipex.com (bengo) wrote:

hi

i can buy regulated power supplies and check them with a multimeter,
if it doesnt work i've just splashed money on adaptors i can use
anyway.

but is it really ok to stick them in series to get -9v? i know i'm
maybe being foolish, and they'll kind of make -9v 0v 9v and 18v
relative to each other, but i just don't see how they won't make 0v 9v
18v and 27v....

The power supplies don't know what you are using as a
ground reference. Assuming each supply is the usual
transformer-isolated type, then you can make any
junction the ground: You can ground the top of
the chain and call the outputs 0, -9, -18, and -27,
or ground the top of the middle for +9, 0, -9, -18,
or whatever you want... everything is relative to
the point you choose as ground.

However, depending on the circuit you are
running, this chain may not be the best way
to operate. That's because the current for
one output must pass through two or more
supplies, so you not only may not get the
current capability you think, but you may
get added ripple, plus modulation of the
high voltage part of the circuit by loads in
the low voltage part. And any current
limiting or other protection will be messed
up as well.

But if you have the supplies or they
are cheap enough, you can always
try your daisly chain and see what happens!






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

[John Fields]

On 6 Apr 2004 01:01:12 -0700, bigben@dsl.pipex.com (bengo) wrote:

any suggestions about what current the adaptors should be?

---
If you're going to post the same message to several newsgroups it
would be better if you crossposted to them instead of posting to them
separately. That way the answers can all be crossposted as well,
without forcing your respondents to visit each group and post their
answers separately.

In this case, my response to your question is at rec.audio.tech.

--
John Fields