FW: [HomeBrew] Powering a laptop from 12 volts...

Fri, 5 Sep 2003 00:25:40 -0700 (PDT)

Ok, now that we already have the easy solutions like
using a 12V UPS or a car inverter that comes ready
with the cigarette lighter adapter to power the 110 v
laptop supply (or any mains operated device), here is
what you could do if you want to do it the hard way 
using your own homebrew gizmo)

Get a 555 timer to oscillate around 120 Hz. Next use
this to clock any JK flip flop and divide the 120 by
2, to get exactly complementary outputs at Q and Q'
outputs of the flip flop, which is now at 60Hz.

Use two mosfets like IRF540 to switch a centre tapped
12 V transformer in parallel inverter configuration
(i.e. connect the centre tap to +12VDC, each of the
12V tappings to each of the Drains of the mosfet, and
gates connected to Q and Q' of the flip flop output,
and both sources of the MOSFET to GND). You can get
120V at the other side of the transformer. Approx
power available is VA rating of the transformer (so if
you use a 3 amp transformer, you can expect to get
about 3x12 VA from this inverter.)

The MOSFET rating is another thing you have to
consider. IRF540 can easily handle this kind of power
without too mmuch heatsinking.

But I would rather go in for the car inverter
available in plenty varieties.

73
Sri, vu2sbj, india

--- George D Wells <[email protected]> wrote:
> ** Please do NOT cross-post messages to multiple
> mailing lists on the "To:" or "CC:" line of the
> e-mail message. **
> 
> 
> 
> -----Original Message-----
> From: George D Wells [mailto:[email protected]] 
> Sent: Wednesday, September 03, 2003 11:41 AM
> To: '[email protected]'; '[email protected]'
> Cc: '[email protected]'
> Subject: RE: [HomeBrew] Powering a laptop from 12
> volts...
> 
> --I power my laptop from a 12v to 117ac converter,
> using the laptops
> home power supply. Rat Shack has them for 29 bucks.
> Simple and you can
> keep the battery charged as well!
> 
> N4MYY
> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of
> [email protected]
> Sent: Wednesday, September 03, 2003 11:17 AM
> To: [email protected]
> Cc: [email protected]
> Subject: Re: [HomeBrew] Powering a laptop from 12
> volts...
> 
> ** Please do NOT cross-post messages to multiple
> mailing lists on the
> "To:" or "CC:" line of the e-mail message. **
> 
> 
> What you need is a DC-to-DC converter. You can
> sometimes find one that
> will suit your needs or build your own, using a
> filament transformer. It
> is a low frequency oscillator stepped up to whatever
> voltage you need,
> then rectified and filtered. Good luck.
> 
> Ed Richards K6UUZ
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> 
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