Rice Cooker Eco-Hack

[AC_Hacker]

Originally Posted by Daox

Have you measured total energy usage with and without the modifications? That would be very interesting to see.

Also, how did you disable the warming feature?

Daox,

You're reading my tattered mind.

I just got back from the store with enough rice to do the trick.

It all means that I'll have to undo the hacks... but anything for science.

Stay tuned...

-AC_Hacker

[Daox]

Any updates here?

[AC_Hacker]

Originally Posted by Daox

Any updates here?

Well, I'm limited by how fast I can eat rice.

But seriously, I wanted to get my datalogger going but I had misplaced the power sensor box I built. Finally found it, and now the batteries in the datalogger don't seem to be holding a charge so well. I'm gonna try to cobble together an AC source with a battery backup.

In the meantime I'm using my kill-a-watt (which continues to really rock), and my post-hack data is running like so:

cooking power = 193 watts (with diode)
cooking time = 1 hour, 24 minutes
cooking kW-h = 0.27 kW-h

Regards,

-AC_Hacker

[Daox]

Updates? I'm quite interested to see if this reduced energy consumption noticeably.

[Ryland]

does this have a timer or something to turn it off? if it doesn't then I would add a bath fan timer switch, when I cook rice on the stove top I tend to turn it off about 15 minutes before it's done and let it finish cooking as it slowly cools down, I never burn rice this way and it's always perfect.

[Piwoslaw]

When I cook rice on the stove I often forget about it, until the water evaporates and it starts to burn...

For central Europe - a potato cooker, that's what I'd like to see Dad-in-law just lives on 'taters...

[AC_Hacker]

Originally Posted by Ryland

does this have a timer or something to turn it off?

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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[AC_Hacker]

Here is the data plot for hacked rice cooker using rice that had been soaked overnight:

It was my assumption that soaking the rice overnight would greatly reduce cooking time. As can be seen from the graphs, the cooking time is reduced, but not greatly. I'm measuring cooking time by the time the power is on. But even with the power cut, the rice will continue to cook for a long time, since it is insulated. Note the long temperature decline curve.

Regards,

-AC_Hacker

[Piwoslaw]

I noticed that the red line (temperature) 'dips' 2 or 3 times in the soaked graph. What could that be?

My theory with soaking overnight is that by morning the rice and water are at room temperature, while if you start with dry rice and pour water in just before cooking, the water will be cooler than room temperature. This means you need slightly more energy to warm the water to room temperature.

[Daox]

Good point Piwoslaw.

Very interesting test results AC Hacker. I too would have thought that soaking would have made a much bigger difference.