[sdiy] Transformer question

[Metzger, Michael A]

I was able to pop the bottom off the toothbrush handle last night. Believe it or
not, inside was as I thought - an air core coil. It is oriented to fit over the
nub on the base. I was surprised at how large the diameter of the air core was.
The engineer was definitely not concerned with making it fit tightly around the
nub. Four leads from the coil go farther into the handle to a circuit board. I
could only see the edge of the board as it was wedged next to the battery.

An interesting detail is that above one side of the coil are two tiny metal
cylinders. Theyblook like magnets. The metal is soft - I chipped one slightly.
They are about 2mm in diameter, maybe 3mm long. The cylinders are next to each
other and are oriented vertically, the same as the coil. They are not in the
core but are 3mm or so directly above the loops on one side of the coil.

So according to everyone's comments it sounds like efficiency is low. The handle
sure is warm every time I pick it up. But hey - the circuit works.

Mike


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Metzger, Michael
A
Sent: Thursday, July 22, 2004 8:54 PM
To: synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] Transformer question


So my quick and dirty "circuit" isn't sound? Uh, no surprise there (look at
ground, cough)  You guys have got me wanting to take the toothbrush apart now. A
quick glance when I bought it showed the handle part to be put together pretty
well. I don't want to break it. Maybe I can get into the base, though. Maybe
something for this weekend.

Mike


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Paul Perry
Sent: Thursday, July 22, 2004 7:45 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Transformer question


You need a closed (or as closed as possible) magnetic loop,
and for any kind of efficiency that means a core of
transformer iron or similar.
All I can imagine working, is two U sections, with the tops
of the Us facing each other across the gap.
(or, similarly, a number of these).

Although, the 'receiving' side could simply be a slab of 
'lossy' magnetic material, if you were just boiling water.

paul perry Melbourne Australia