[sdiy] Low current power supply?

[dj hohum]

Hi Alan,

On 7/17/07, Needham, Alan <Alan.Needham at centrica.com> wrote:
> The idea of a capacitor as a voltage dropper is something I've seen
> a fair few times in published circuits, I guess you just need to
> make sure the cap is happy with your mains p-p voltage and can
> handle the ripple current - nothing difficult.
> I wonder about the choice of isolation transformer though - probably
> OK but just leaves me a bit .... nervous, I don't want ANY more
> mains shocks this lifetime !

Yes, I thought about what might be a good choice. I've seen it
suggested before that small audio transformers work just fine. It
occurred to me though that modem transformers are designed to handle
ring voltage and to protect the computer from same. They might not be
ideal, but I think that they're probably reasonably safe.

> The idea certainly sounds safer than a frequency doubling circuit
> with harmonics to infinity and beyond - makes me feel sorry for
> the transformer !

Well I believe all of that was just to improve the power transfer
capability of the cap to give a bit more output current. Since I need
just a few ma, that's all overkill as well.

tnx,
Daryl