Power supply design

[Dejan Uzelac]

Hi.

I have an adapter with an output of 9V 1A DC adapter.

I need to convert this to 5V, 2A?

Any idea how I can make a little power supply circuit or something to
achieve this?

THANX

 

Dejan Uzelac wrote:

Hi.

I have an adapter with an output of 9V 1A DC adapter.

I need to convert this to 5V, 2A?

Any idea how I can make a little power supply circuit or something to

achieve this?

THANX

Can't be done. Your adapter supplies 9W and you want to supply 10W. As
someone said, it would need to over 100% efficiency which is
impossible.

 

[John Woodgate]

I read in sci.electronics.design that Dejan Uzelac
<uzelac@optushome.com.au> wrote (in <420acba2$0$1022$afc38c87@news.optus
net.com.au&gt about 'Power supply design', on Thu, 10 Feb 2005:

Hi.

I have an adapter with an output of 9V 1A DC adapter.

I need to convert this to 5V, 2A?

Any idea how I can make a little power supply circuit or something to
achieve this?

You can't. 9 V x 1 A is 9 watts. 5 V x 2 A is 10 watts. You can't get

more out than you put in.

The best thing to do is to buy a 5 V 2 A adapter.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

On 14 Apr 2005 04:07:30 -0700, bigcat@meeow.co.uk wrote:

Adrian Tuddenham wrote:
bigcat@meeow.co.uk> wrote:

[variac]

Now make a sliding knob with a wide carbon brush on the bottom,
make it
run along this track. The brush must be wide so as not to produce
much
turn shorting current. A slotted brush or 2 brushes would be
better.

The carbon of a variac brush is fairly high resistance so that it can
operate in contact with more than one turn at a time without giving
rise
to huge circulating currents. This allows smoother voltage control
without breaks between the steps.


If you had 2 MOT cores, one could run the 2 in series, both with linear
slider taps, with the 2 carbon brushse connected to the one handle so
that as the lst turn of one is contacted, the first turn of the next TF
is contacted, thus giving twice the number of effective taps, or v
resolution. WOuld give something like an 8" long tap off path, and
fairly smooth V output.


NT

I happen to have a 12A variac, old and heavy duty, may give it a shot
as a pre-regulator, keep the input voltage as low as possible.

Thanks for the suggestions everyone,
Steve

 

[John Crighton]

On Thu, 14 Apr 2005 17:18:25 -0500, steve wrote:

I happen to have a 12A variac, old and heavy duty, may give it a shot
as a pre-regulator, keep the input voltage as low as possible.

Thanks for the suggestions everyone,
Steve

Hello Steve
I would be interested to find out what the primary idling current
is when you when you connect the variac up to the primary
of your MOT. No load on the secondary.

I am guessing that you are in America.
Just wondering if hobbyists with a 60 Hz supply are much
better off than hobbyists in 50Hz countries in regard to
salvaging MOTs. If you have a multimeter can you
let me know. Thanks.

Primary Volts Primary current
120V
115V
110V
105V
100V
95V
90V

Regards,
John Crighton
Sydney (240V 50Hz)