14 Jan
2006
14 Jan
'06
10:45 a.m.
On 1/14/2006 at 11:09 AM gordonjcp at gjcp.net wrote:
Surely a transformer would need to be powered all the
time?
So what? Your central heating system and doorbell have one. Much, if not
most, modern electronic equipment, such as PCs, televisions, etc. all have
some tiny draw from the AC mains even when powered off. If all you
needed was a very small DC supply you could do away with the transformer
and perhaps use a couple of capacitors in series with each side of the
line, followed by a rectifier and a zener--it wouldn't provide quite the
isolation from the line that would be ideal, but it wouldn't need a
transformer.
Cheers,
Chuck