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Resistance of rice cooker's heating element?

  1. Dec 12, 2016 #1
    hi everyone,

    i need some help with my project that is DC rice cooker. i have the same problem for my calculation and logic cause my rice cooker use 12V and 100Watt. is that mean i need to use 8.3333Amp for the current? or i need to design a circuit that can reduce the amount of current needed?. as u all know, large amount of current could probably leading to danger and it could be damaging my circuit or heating element. can you suggest me a design for my 12V DC rice cooker? . hope you can share some idea.

    -dinie

    i have included my email if there anybody can help me for this project. thank you

    [ mod note: email addresses not allowed in posts ]
     
    Last edited by a moderator: Dec 12, 2016
  2. jcsd
  3. Dec 12, 2016 #2

    haruspex

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    Your design will set the resistance, the power source will set the voltage. The power generated is a consequence. If you are given 12V and want 100W choose the resistance accordingly.
     
    Last edited by a moderator: Dec 12, 2016
  4. Dec 12, 2016 #3

    NascentOxygen

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    Hi Dinie. I have moved your post into the homework forum as it resembles a homework exercise. If you are not a student let me know.

    Have you already decided on a way to construct your cooker, and all you need help with is the heating element itself?
     
  5. Dec 13, 2016 #4
    how can i choose the resistance while i need to gain 100W for the heating element?
    if i choose the resistance, what will happen to the load?

    thank you for the reply.
     
  6. Dec 13, 2016 #5

    NascentOxygen

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    "load" is just another name for the heating element here.
     
  7. Dec 13, 2016 #6
    hi,
    yup, i am pursuing an undergraduate degree in electrical engineering. this project was my final year project.

    i have already decided a design for my rice cooker. basically i want supply for the rice cooker by using low voltage DC supply. thus, i use 12V for my design. but the heating element that i choose is 100Watt. For a basic calculation, the current must be high because i used lower voltage. so, what can i apply for the circuit to reduce the current (if it possibble). or i need to use other design?
     
  8. Dec 13, 2016 #7
    yes, i know that. what will happen to the heating element, if i choose some resistance in the circuit. is that mean, the rice cooker need more time to cook the rice?
     
  9. Dec 13, 2016 #8

    NascentOxygen

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    Using 12V, if you need 100W then there is no escaping a current drain of 8A. Have you looked at the power used by mains-powered rice cookers to see whether 100W is the right ballpark figure you should be designing with?

    Are you saying that 8A is going to be too much current for your situation? I can think of a couple of ways you could make a rice cooker that gets by on less power. Think about it yourself and post your ideas for building a rice cooker that needs less power, less current.
     
  10. Dec 13, 2016 #9

    haruspex

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    Are you saying that the heating element you have chosen claims to be 100W? If so, that is based on a specification of the voltage to be used. If that is 12V then fine, but if it specifies 24V and you only supply 12 then you won't get 100W, you will only get 25W.

    For a 12V supply and 100W output you must choose an element that has the right resistance for that combination. You can choose an element with a higher stated power output if the resistance Is right. E.g. if it states 400W and 50V supply that would work. However, it might be dangerous to use an element that quotes less than 100W even if the resistance is right.
     
  11. Dec 13, 2016 #10

    NascentOxygen

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    There is no point adding extra external resistance, in an attempt to reduce the current drain. Your extra resistance wastes heat outside the cooker, and your 100W element will not get so hot and it will take longer to cook, or may not be hot enough to cook the rice at all.
     
  12. May 18, 2017 #11
    Thanks for all the suggestion and opinion.Now, i am done creating one of my DC rice cooker. My rice cooker come out with 2 mode of cooking, that is keep warm and normal cooking. I used two heating element and connect it in parallel circuit, thus, each of my heating element will consume 50Watt. Therefore, for normal cooking, i will used both of the heating element and that mode will consume 100Watt, while "keep warm" mode will only used 50Watt of power. I learn that the lower the resistance used for heating, the greater the heat energy will produce.
     
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