Power supply design

D

Dejan Uzelac

Guest
Hi.

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much for
my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power supply
circuit?

THANX
 
"Dejan Uzelac"
I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power
supply circuit?
Click to expand...

** You did not look very hard - this one from Jaycar is only $ 23.95.


http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647





.............. Phil
 
Phil Allison wrote:
"Dejan Uzelac"

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power
supply circuit?



** You did not look very hard - this one from Jaycar is only $ 23.95.


http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647





............. Phil
Click to expand...
Rockby have 5V 2.6A plug packs for $5 at the moment.
 
"Matthew Gunn"
Phil Allison wrote:


** You did not look very hard - this one from Jaycar is only $ 23.95.

http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647



Plus a power lead @ $6.70. Still cheap @ $30.
Click to expand...

** $2.25 from WES - plus lots of folk have one lying around from some
deceased piece of gear.



.............. Phil
 
On Thu, 10 Feb 2005 13:46:40 +1100, "Dejan Uzelac"
<uzelac@optushome.com.au> wrote:

Hi.

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much for
my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power supply
circuit?

THANX
Click to expand...
Hello Dejan,
with the idea of saving money in mind, how about using
an old computer power supply. You could probably find
or bludge one for free. 5V able to supply lots of amps.

http://academic1.bellevue.edu/robots/powerSupply/
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM#TIPS

Those two articles above talk about loading the 5V
supplies slightly. I found some power supplies that worked
OK without using the extra load resistors, may be you will
too and you wont even have to open the box.

Smaller box.
For just 2 amps, you could take the board out of the metal
box, cut off most of the wires that you dont need and fit
the power supply board to a smaller box without the fan
and fancy connectors. Just a thought. Have Fun.
Observe the usual safety precautions.
Andrew M can fill you in on those. :)

Regards,
John Crighton
Hornsby
 
True true...
well.. I have to admit it was a bit of a challenge, rather to make it work
on my own!

But.. yes,, rockby have the 5V 2.6A on sale now for $3.
Thats just ridiculously cheap!

Thanx Swanny

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:37034jF4u3qe8U1@individual.net...
"Dejan Uzelac"

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power
supply circuit?


** You did not look very hard - this one from Jaycar is only $ 23.95.


http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647





............. Phil
Click to expand...
 
Interesting idea...
Well.. I do want something compact.
Im using this to power a router I got from US.
Belkin.. I called them up and they said they cant help.
They have no 'spare parts'.
So I think Ill just stick to buying one now that there is some so cheap!

But still.. a very good idea for future!

Thanx! ;-)

"John Crighton" <john_c@tpg.com.au> wrote in message
news:420ad781.28706020@News.individual.net...
On Thu, 10 Feb 2005 13:46:40 +1100, "Dejan Uzelac"
uzelac@optushome.com.au> wrote:

Hi.

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for
my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power
supply
circuit?

THANX


Hello Dejan,
with the idea of saving money in mind, how about using
an old computer power supply. You could probably find
or bludge one for free. 5V able to supply lots of amps.

http://academic1.bellevue.edu/robots/powerSupply/
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM#TIPS

Those two articles above talk about loading the 5V
supplies slightly. I found some power supplies that worked
OK without using the extra load resistors, may be you will
too and you wont even have to open the box.

Smaller box.
For just 2 amps, you could take the board out of the metal
box, cut off most of the wires that you dont need and fit
the power supply board to a smaller box without the fan
and fancy connectors. Just a thought. Have Fun.
Observe the usual safety precautions.
Andrew M can fill you in on those. :)

Regards,
John Crighton
Hornsby
Click to expand...
 
On Thu, 10 Feb 2005 04:25:00 +0000 (UTC), Wing Fong Wong
<wing@tart.com.au> wrote:



Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au
Click to expand...

Hello Wing,
that is interesting, tell me your experiences.
How bad was the instability that you found?
Regards,
John Crighton
Hornsby
 
John Crighton <john_c@tpg.com.au> wrote:
Hello Dejan,
with the idea of saving money in mind, how about using
an old computer power supply. You could probably find
or bludge one for free. 5V able to supply lots of amps.

http://academic1.bellevue.edu/robots/powerSupply/
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM#TIPS

Those two articles above talk about loading the 5V
supplies slightly. I found some power supplies that worked
OK without using the extra load resistors, may be you will
too and you wont even have to open the box.

Smaller box.
For just 2 amps, you could take the board out of the metal
box, cut off most of the wires that you dont need and fit
the power supply board to a smaller box without the fan
and fancy connectors. Just a thought. Have Fun.
Observe the usual safety precautions.
Andrew M can fill you in on those. :)

Regards,
John Crighton
Hornsby
Click to expand...

Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au
 
"Matthew Gunn"
Wing Fong Wong wrote:


Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

I'm curious too. I was under the impression that a computer power supply
had to be well regulated so that the computer would work properly.
Click to expand...

** The high current, 5 volt rail has the PWM feedback loop stabilising it
while the others do not and are unregulated.

If the 5 volt rail is not sufficiently loaded the PSU may not even run.

If the others are unloaded or lightly loaded their voltage can be high by
possibly 20%.




............ Phil
 
John Crighton <john_c@tpg.com.au> wrote:
On Thu, 10 Feb 2005 04:25:00 +0000 (UTC), Wing Fong Wong
wing@tart.com.au> wrote:



Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au


Hello Wing,
that is interesting, tell me your experiences.
How bad was the instability that you found?
Regards,
John Crighton
Hornsby
Click to expand...
Perhaps stablility was not quite the right in the strictest sense of the
word. Its stable, just that the voltage vary a bit for sensitive
circuitry. So far as my experience, it all hearsay. I was reading a similar
topic on comp.sys.cbm where someone want to make a C128 PS from an ATX
supply.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au
 
Phil Allison <philallison@tpg.com.au> wrote:
"Matthew Gunn"
Wing Fong Wong wrote:


Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

I'm curious too. I was under the impression that a computer power supply
had to be well regulated so that the computer would work properly.



** The high current, 5 volt rail has the PWM feedback loop stabilising it
while the others do not and are unregulated.

If the 5 volt rail is not sufficiently loaded the PSU may not even run.

If the others are unloaded or lightly loaded their voltage can be high by
possibly 20%.




............ Phil
Click to expand...
Thanks for the explantion Phil. I think I just grew smarter :)

--

Wing Wong.
Webpage: http://wing.ucc.asn.au
 
Phil Allison wrote:
"Dejan Uzelac"

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for my application.

Highest output current adapter I have is a 9V 1A DC adapter.

Any idea how to convert this to 5V, 2A? how can I make a little power
supply circuit?



** You did not look very hard - this one from Jaycar is only $ 23.95.


http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647





............. Phil






Plus a power lead @ $6.70. Still cheap @ $30.
Click to expand...
 
On Thu, 10 Feb 2005 13:46:40 +1100, "Dejan Uzelac" <uzelac@optushome.com.au>
wrote:

Hi.

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much for
my application.
Click to expand...
A 5V DC 3A regulated switchmode wallwart will set you back a whopping $3.50 at
Rockby. Their stock# 32020

http://www.rockby.com.au
 
Yes... realised that!

Already have an order in :)


"budgie" <me@privacy.net> wrote in message
news:s2lm019ujlthaao2eb26vvhm3dqdurm3tv@4ax.com...
On Thu, 10 Feb 2005 13:46:40 +1100, "Dejan Uzelac"
uzelac@optushome.com.au
wrote:

Hi.

I need an adapter with an output of 5V 2A DC. I cant seem to find it
anywhere, and even if I do it costs minimum $50. Well, thats a bit much
for
my application.

A 5V DC 3A regulated switchmode wallwart will set you back a whopping
$3.50 at
Rockby. Their stock# 32020

http://www.rockby.com.au
Click to expand...
 
Phil Allison wrote:
"Matthew Gunn"

Phil Allison wrote:


** You did not look very hard - this one from Jaycar is only $ 23.95.

http://www1.jaycar.com.au/productView.asp?ID=MP3230&CATID=27&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=647



Plus a power lead @ $6.70. Still cheap @ $30.



** $2.25 from WES - plus lots of folk have one lying around from some
deceased piece of gear.



............. Phil



True. I was just making sure he realised he needed a cable too.
Click to expand...
 
Wing Fong Wong wrote:
John Crighton <john_c@tpg.com.au> wrote:

Hello Dejan,
with the idea of saving money in mind, how about using
an old computer power supply. You could probably find
or bludge one for free. 5V able to supply lots of amps.

http://academic1.bellevue.edu/robots/powerSupply/
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM#TIPS

Those two articles above talk about loading the 5V
supplies slightly. I found some power supplies that worked
OK without using the extra load resistors, may be you will
too and you wont even have to open the box.

Smaller box.
For just 2 amps, you could take the board out of the metal
box, cut off most of the wires that you dont need and fit
the power supply board to a smaller box without the fan
and fancy connectors. Just a thought. Have Fun.
Observe the usual safety precautions.
Andrew M can fill you in on those. :)

Regards,
John Crighton
Hornsby





Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

I'm curious too. I was under the impression that a computer power
Click to expand...
supply had to be well regulated so that the computer would work properly.
 
"Phil Allison" <philallison@tpg.com.au> wrote in message
news:370ab0F58egjiU1@individual.net...
"Matthew Gunn"
Wing Fong Wong wrote:


Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

I'm curious too. I was under the impression that a computer power supply had
to be well regulated so that the computer would work properly.

The high current, 5 volt rail has the PWM feedback loop stabilising it while
the others do not and are unregulated.
Click to expand...
More stricty they track the 5 volt rail which is regulated.

If the 5 volt rail is not sufficiently loaded the PSU may not even run.

If the others are unloaded or lightly loaded their voltage can be high by
possibly 20%.
Click to expand...
Bullshit.
 
On Thu, 10 Feb 2005 04:52:58 GMT, john_c@tpg.com.au (John Crighton)
put finger to keyboard and composed:

On Thu, 10 Feb 2005 04:25:00 +0000 (UTC), Wing Fong Wong
wing@tart.com.au> wrote:



Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au


Hello Wing,
that is interesting, tell me your experiences.
How bad was the instability that you found?
Regards,
John Crighton
Hornsby
Click to expand...
Only the very high end PSUs appear to have independent regulation for
each of the supply rails. IME most PC PSUs regulate by sensing a
weighted average of the +5V and +12V rails. This means that load
variations on the +12V rail will affect the +5V supply. See this ATX
example:
http://www.pavouk.comp.cz/hw/en_atxps.html

Notice R25 and R26 in the feedback path. Whenever I modify a PC PSU
for +6V or 13.8V, I remove the appropriate resistor and recalculate
the remaining one.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
On Fri, 11 Feb 2005 07:52:53 +1100, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:

On Thu, 10 Feb 2005 04:52:58 GMT, john_c@tpg.com.au (John Crighton)
put finger to keyboard and composed:

On Thu, 10 Feb 2005 04:25:00 +0000 (UTC), Wing Fong Wong
wing@tart.com.au> wrote:



Only problem with computer PS are that the voltages aren't always too
stable - especially cheap ones.

--

Wing Wong.
Webpage: http://wing.ucc.asn.au


Hello Wing,
that is interesting, tell me your experiences.
How bad was the instability that you found?
Regards,
John Crighton
Hornsby

Only the very high end PSUs appear to have independent regulation for
each of the supply rails. IME most PC PSUs regulate by sensing a
weighted average of the +5V and +12V rails. This means that load
variations on the +12V rail will affect the +5V supply. See this ATX
example:
http://www.pavouk.comp.cz/hw/en_atxps.html

Notice R25 and R26 in the feedback path. Whenever I modify a PC PSU
for +6V or 13.8V, I remove the appropriate resistor and recalculate
the remaining one.


- Franc Zabkar
Click to expand...

Hello Frank,
thanks for pointing that out. Great to see actual diagrams
and descriptions. That url is now in the favourites. :)
Regards,
John Crighton
Hornsby
 
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