[sdiy] ad633 fun, psu

[harry]

Hi Matti: inline

matti wrote:

> so, having recieved my ad633's, I decided to use them. using the fatman's
> +8/-12 power, the output sounds much more like the two inputs summed, than
> multiplied. I've tried both the simple ad633 circuits floating around, and
> opamp gain stages fr the inputs. Anybody?

pass...

> I have two wall warts for use here, 12VAC and 10VAC outputs. Is it
> possible to use the two together as a 22VAC Power supply?

Yes... this is AC remember....

> Should one lead
> from each be tied to each other?

Yes... so the two transformer secondaries are in series. You also need to
connect the  RIGHT lead so that the outputs are in phase. This might be a
problem
later if you can reverse the wall wart primaries in the wall socket (say THAT
fast
ten times...).  Reversing either primary or secondary phase will cause
troubles.

> For ground, would it be better to use a
> trim pot to adjust the point at which the two transformers are tied to
> each other,

bad idea...

> or leave this floating,

probably bad idea...

> and use capacitors between the the
> remaining leads?

bad idea also...

I assume that you want to make a DC supply out of this, correct ? Did you want
a
single or a dual supply?

For a single... tie the transformers in series... do NOT connect the center
lead to
anything. Add a bridge rectifier and one large cap and you are there. Expect
the
22VAC * 1.4 = DC Voltage. Under light load this will be even higher !!!  So
probably as much as 40VDC might be expected.

For a dual... use the same bridge rectifier and two capacitors. The common
point
of the capacitors is tied to the center lead of the transformers.  The
positive and negative voltages will not be equal because the inputs are not
equal. But it will work.

This is a rather desperate way to get a power supply... Finding a wall wart
with a center tap might make it easier.  I like to BUY power supplies usually,
though I have
built a few. Keep your eyes on the surplus market and you can find +/- 12V or
+/-
15VDC linear supplies for around $20. Mow lawns during the time you've saved
and
you'll even turn a profit

(or pay for the experience and... er... DIY ???)

I did build my own supplies in my early days. They do work and you will
learn...

H^)   harry   (the wealth of middle age can be a curse... but that is the
wages of having much less DIY time...)

>
>
> thanks
>
> -
> finland red
> germany black
> egypt white