Question on Oral-B toothbrush charger

[Zhang]

Has anyone used an Oral-B power toothbrush (7000 or 8000 series)?
I have one and it uses normal 110V power to charge Ni-MH battery.
The interesting thing is its charger interface. The charger base
has a protruder and the toothbrush has a corresponding receptacle,
which match each other for charging. However, both the protruder
and the receptacle are made of plastic material, i.e. non-conductor.
I measured them using my multimeter and it shows no voltage, no
current and infinite resistance, confirming that they are indeed
non-conductors. So the questions is, how is charging done with
non-conducting interface?

You may reply here or to my mailbox, thanks.

 

[Jim Thompson]

Has anyone used an Oral-B power toothbrush (7000 or 8000 series)?
I have one and it uses normal 110V power to charge Ni-MH battery.
The interesting thing is its charger interface. The charger base
has a protruder and the toothbrush has a corresponding receptacle,
which match each other for charging. However, both the protruder
and the receptacle are made of plastic material, i.e. non-conductor.
I measured them using my multimeter and it shows no voltage, no
current and infinite resistance, confirming that they are indeed
non-conductors. So the questions is, how is charging done with
non-conducting interface?

You may reply here or to my mailbox, thanks.

Probably like my Panasonic shaver... transformer halves with air-gap.

...Jim Thompson

 

[petrus bitbyter]

Has anyone used an Oral-B power toothbrush (7000 or 8000 series)?
I have one and it uses normal 110V power to charge Ni-MH battery.
The interesting thing is its charger interface. The charger base
has a protruder and the toothbrush has a corresponding receptacle,
which match each other for charging. However, both the protruder
and the receptacle are made of plastic material, i.e. non-conduct
I measured them using my multimeter and it shows no voltage, no
current and infinite resistance, confirming that they are indeed
non-conductors. So the questions is, how is charging done with
non-conducting interface?

You may reply here or to my mailbox, thanks.

Ever opened a brush like that. Found a coil at the bottom that was connected
to a rectifier and loading circuit. The loader provides a magnetic field of
about 22kHz that is conducted by a kind of a pin that goes right through the
center of the coil. You can see something of its working when you place the
loader with a brush in place put on an steel (iron) surface. The load LED
will dim.

petrus bitbyter

 

[Zhang]

Transformer with air core? Hmm ... that sounds right.

The base has a block with size of a typical household transformer where
the 110V comes in. It should be the place that transformes 110V AC to
1.2V AC, I can feel the heat by touching the cover.

The protruder/receptacle interface should then form another transformer
where 1.2V AC is coupled into the second coil inside the toothbrush,
and further rectified to 1.2V DC to charge the battery.

Considering the small size of that interface, it's pretty neat design.