Quote:
Originally Posted by Ryland
does this have a timer or something to turn it off?
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I have left the original mechanism in place for now.
The principle of operation is based on behavior of certain materials that posess magnetic properties. When they are heated, their magnetic property is essentially unchanged until a critical temperature is reached. At that critical temperature, the magnetic property is suddenly lost completely. When the material cools back down below the critical temperature, the magnetic property returns completely.
In a rice cooker, the magnetic material is affixed to a spring-loaded arm that presses a microswitch. When the rice cooking pot is in the cooker and the rice cooker is turned on, the spring loaded arm is brought up until the magnet material sticks to a small steel disk. When the rice is cooking, the temp goes to 212 degrees F, but doesn't go over. When the free liquid water is taken up through absorption by the rice and through boiling off, the temp goes up enough that the magnetic material loses its magnetic property, the spring loaded arm drops, and the microswitch opens, which cuts power to the cooker.
Pretty clever switch, safe and very reliable.
I have so far completed one logged test cycle, with un-soaked rice, with the diode and insulation in place.
Here is a graph of that data:
I haven't scaled the data, but there's still something here to learn...
Green line is power. minimum value = 0 watts, maximum value = 193 watts
Red line is cooking temperature (probe was about in the center of the cooking area). minimum value = 64 degrees F, maximum value = 212 degrees F.
Blue line is ambient temperature. Center value is 70 degrees F.
Regards,
-AC_Hacker
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