[sdiy] Filtering noise from power inverter in the van studio...

[Ken Stone]

One thing I can actually claim is having made a 500VA Sine wave inverter
from the ground up. SCR switching in push-pull on a center tapped coil on a
ferro. In my shed I have the first transformer made for the project - which
has a single coil for bridge opperation. More than just an inverter too - it
was actually a UPS/SPS.

Ken

>On Tue, Jul 11, 2006 at 01:35:00AM -0700, Bob Weigel wrote:
>> The inverter makes a horrible amount of noise with this setup...a bad 
>> buzz.  Before when I did it with a lower power inverter I only got 
>> significant noise when I ran my DSP digitech units.  However this time 
>> even w/out the peavey fx I'm running on the floor it still makes about 
>> the same amount of noise...even powering the amp separately.  Hmm.  This 
>> is a 1000W rms inverter from a fairly decent company I think.  Can't 
>> think of it off the top.  But anyway I suppose a ferro-resonant 
>> transformer setup would be ideal but is there a cheaper way to get rid 
>> of this anyone has had experience with? Thanks, -Bob
>
>The magic words are "Sine Wave Inverter".  Cheap too, only seem to run
>around 80cents/watt.  I bet if you throw a scope on the smaller Inverter it
>has more steps then the larger one.  I've got a 1500watt cheap one ( $129 )
>and a 200watt more expensive one ( $150... go figure ) and the cheap one is
>a *SQUARE* wave.  It wont drive fluorescent lights!  Heck, it wont even run
>some power tools safely and thats what I got it for...  the more expensive
>one is specifically for electronics and is 64step which isnt exactly pretty
>but is at least quiet.
>
>Seriously, the cheap inverters are usually square wave or stepped sine with
>only a few steps.   The more money you pay, the more steps until you get the
>the large rackmount units ( you'll find they come mostly from places
>specializing in Solar Power ) which do nice pure sine output.
>
>Could build your own!  a nice 60cycle oscillator driving a couple good'ol
>2N3055's, then drive your favorite 12VAC 10amp transformer backwards...  I'm
>sure the efficiency wouldnt be great but it'd be quiet.
>
>-- 
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_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
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