Re: Transformerless PSU using a zener/transil to drop voltage

[Alex <christiansen_alex@xxxxxxxxxxx>]

On May 29, 6:01 pm, and...@xxxxxxxxxxxxxxxx wrote:
> Hi all,
>
> For a hobby home automation system I need to make a very small, non
> isolated, direct-mains power supply unit regulated via a 7812 IC or such.
> Thus it has to be transformer-less, and since I need to draw something
> like 100mA, even a capacitor (of the kind that do not explode on mains!)
> would be too big. I have two ideas so far to lower the voltage to a range
> acceptable by the 7812:

could also use a lightdimmer !! the TRIAC  or SCR  could be a solution
as it do not dissipate much power   . Maybe it can be a problem to
filter the voltage from the TRIAC/lightdimmer  as the consumption is
100 mA  but I guess it will be the same if a FET is on only until the
voltage are over say 20 volt
i