[sdiy] 12VDC to 12VAC converter [OT]

[harrybissell at wowway.com]

I'd say that a square wave has an RMS value (area under the curve)
equal to the 'peak' value. 

So a 24V peak to peak square wave would not be equal to a 12VAC RMS
sine wave. Its way more imho...

H^) harry


On Tue, 04 Sep 2007 11:21:12 +0100, Seb Francis wrote
> ASSI wrote:
> > On Montag 03 September 2007, Seb Francis wrote:
> >   
> >> I need to produce a 12VAC 20VA 50Hz supply from a 12VDC input.  It's
> >> to run a 12VAC motor from a car battery, so the AC voltage doesn't
> >> have to be particularly sine-like or regulated.
> >>     
> >
> > Look for a PWM driver for appliance motors, preferrably with an 
> > integrated H-bridge and just feed it an unmodulated 50Hz (or whatever 
> > is close enough) signal.  Rolling your own is entirely possible at 
> > roughly 2A, but then you have to deal by yourself with controlling the 
> > dead-time during the switching event and with the reactance from the 
> > motor coils.  If you do roll your own controllers, there are ready-made 
> > H-bridge or half-bridge IC, both bipolar or MOSFET and with or without 
> > the driver circuitry from many companies.  Just the bridge drivers are 
> > available seperately, too.  There's a stub entry on Whackypedia that 
> > has a few external links that may be helpful:
> >
> > http://en.wikipedia.org/wiki/H-bridge
> >
> > Google brings a lot of useful links on that topic as well.
> >
> >
> 
> Ah that makes a lot of sense .. it's still going to be a square wave
> 
> (not sine) fed to the motor, but it will be effectively 24V peak to 
> peak which (being a square wave) should be equivalent to 12VAC RMS.
> 
> Looks like it would be a nice simple circuit too.  Thanks!
> 
> Seb
> 
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Harry Bissell & Nora Abdullah 4eva