On Fri, 06 May 2005 19:37:58 GMT, Be
wrote:

Anyway, normally, when this switch is pressed down, it clicks and locks into
position and a light comes on. After 30 minutes the switch releases and the
rice is done. There is no timer that I can see in the unit - it must have to
do with the expansion of some metal trigger from heat over that time frame.


Took some effort to figure that out. The circuit switch is held
closed by a curie point magnet underneath the central circular cup.
So long as the rice is aboil the temperature will remain around 100
deg C, the boiling point of water. When the rice is cooked and fairly
dry the temperature rises rapidly. Somewhere around 200 deg C say,
the curie point of the magnet will be exceeded and the magnet will
lose its magnetism. The spring below the circular cup pushes the cup
up and breaks the circuit. With the circuit open the pot contents
will cool and fall below the curie temperature. The switch is ready
to be set again if you want to warm up the rice.

The pot must be sized to your cooker as per manufacturer. I had once
substituted a less battered pot from another brand rice cooker. The
strange things began to happen. At first it took longer to cook. Then
it would undercook, leaving half raw rice when the switch triggered
open.. I had to swith it on again to finish the cooking. Then I
noticed one of the cooker's legs had sagged/melted. I took a look at
the heater element and the aluminum had melted in places too. The
cooker was toast. Took a few minutes to realise that the substiitute
pot's bottom didn't fully conform to the heater element. The heat
transfer rate was lessened. Thus the heater had to work harder to boil
off the water (longer cooking time.) By repeated switching on again
to finish the cooking, bit by bit the element became hot enough to
melt the aluminum and the plastic leg.