RE: 9VAC from 5VDC?

From: Bil Herd <>
Date: Fri, 13 Sep 2013 22:57:48 -0400
Message-ID: <>
Do you want to create AC from DC or from AC? (thought is was 5 VDC as

-----Original Message-----
[] On Behalf Of Jim Brain
Sent: Friday, September 13, 2013 10:12 PM
Subject: Re: 9VAC from 5VDC?

On 9/13/2013 8:25 PM, john/lori wrote:
> Magnetics are traditionally black magic, but transformers aren'
> all that hard.
> I assume you're talking 5VDC so you want a transformer that's more
> like 2.6 : 1 (9VAC is 12.73 peak)
I'd be happy with 1:2 (yes, it'd be a bit low, but it would work for the
things in the machine that care (sine wave for TOD, 9V unregulated which
is turned into 6.2V for Cassette.  What, about 8V RMS at the user port,
I'd be OK with that.

> Assuming you're dead set against just using a 9VAC wallwart or
> something next to your 5VDC, I think I'd try 5VDC to ~ +-13VDC then
> synthesize the 9VAC from that.
> The cheap inverters use a wave form something like this.
>    _       _       _
>  _| |_   _| |_   _| |_
> |     |_|     |_|
I can do a good sine wave with a uC.  No worries there.
> If you were going to wind your own transformer you could give it more
> steps.
I want something I can buy, as I assume, if this works, lots of people
with dodgy PSUs will want to replicate it.  I could double/triple the
voltage using a doubler/tripler and use a 1:1 isolation if needed, if a
1:1 was easily sourceable, and a 1:2 was not, but that's more components
and more things to solder up incorrectly.

So, a nice 1:2 or 1:3 transformer that will work in the use case would be
ideal, something I can buy off the shelf.


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Received on 2013-09-14 04:00:13

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