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temperature sensor LM35

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by civictypeR, Dec 6, 2007.

  1. civictypeR

    civictypeR New Member

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    Hey guys , i am designing a project which requires LM35 temperature sensor , generally the output from the sensor voltage is in analogue form and the reading i got from the multimeter is too small . Basically is about 300mV like this . Is this voltage sufficient to be detected by the PIC 16F877 ? And i dont know how to provide heat to the sensor so that i can come out a chart of temperature versus the output voltage . My most important range is between 25 till 35 degree celcius. Thanks guys and feel free to give comment

    CivictypeR
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    The LM35 is calibrated to give 10mV/Cdeg over a standard range of +2C thru 150C.
    The 10mV/C signal can be connected to the ADC input of the PIC.

    To provide test heat, grip the LM35 between your finger and thumb.

    EDIT: so at 25C, Vsig = 25 * .01 = 0.25V and 35C, 35 * .01 =.35v
     
    Last edited: Dec 6, 2007
  3. browningbuck

    browningbuck New Member

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    ohhhh this is my next project after my fuel gauge, i am very intrested (if you had time would you throw up you diagram?)
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Look at this pdf, its a way to amplify the signal from the LM35
     
    Last edited: Jul 7, 2008
  6. tanoflash4

    tanoflash4 New Member

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    LM35 Signal Conditioning Circuit

    Hi! Can someone show me how to make a signal conditioning circuit for my LM35. I needed a 0-3.3v output in order to interface it with Zilog. Tnx!
     
  7. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Look at my recent pdf circuit post on this thread. 6th Dec07
     
  8. Super_voip

    Super_voip New Member

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    Why not use a digital sensor, maybe something from the I2C range? This would save a lot of additional circuitry and an LM73 or LM75 would seem to be supported. Or is this a school project?
     
  9. ☼☺☼coool☼☺☼

    ☼☺☼coool☼☺☼ New Member

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    sooo easy dear


    hey all, look dear :
    as I got from your message that you are gonna use pic 16f877 ok then I advice you just to take this prog. cut and paste it in the pic basic pro program and just run it so you will get the reading from the lm35 on an LCD...
    hope you got it...
     

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  10. pete

    pete New Member

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    the same prob goes to me also. i'm also designing the same lm35 but i use 2 lm35 and interface with pic16f877.. i tend to use c languange since it is easy to understand..can somebody help me with this...at least show me how to read the input and display it to lcd.... :)
     
  11. Boncuk

    Boncuk New Member

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    ... to consider that the basic circuit starts at 2deg/C

    Hans
     
  12. Boncuk

    Boncuk New Member

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    Hi civictypeR,

    there is another easy approach to use the LM35 for an MCU circuit. Use a current source from 4 to 20mA.

    Depending on the burden resistance (500Ω) the output will be 2 to 10V for 0 to 100deg/C or 1 to 5V using 250Ω.

    Here is an example as used in the data sheet.

    Boncuk
     

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  13. zenaa.m

    zenaa.m New Member

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    I need to help to solving this assignment, please if you know help me

    Use the names Element, My integer, MyChar and Sequence for your class definitions.
    Note that there is an is_a relationship between Element and My integer, MyChar and Sequence classes.
    • Define constructer for each class My integer objects are initialized to 0, MyCar objects to 0, and Sequence to an empty sequence with zero elements.
    • Define Necessary prosperities for Char and integer
    • You might need another class that allow you to have a sequence depending on your implementation.
     
  14. Hayato

    Hayato Member

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    I think you posted in the wrong thread.
     
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Hi reynn,
    The pdf you requested in the PM.:)
     
  16. GonzoEngineer

    GonzoEngineer New Member

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    We use a lot of LM35's where I work. If your leads are long, you can sometimes get oscillations on the output signal.

    If I were you, I would amplify it for a gain of 10 for a better signal, and use some filtering on the input.
     
  17. reynn

    reynn New Member

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    sir im not familiar with the 5V1Z Op clamp in your circuit, could you please explain this to me. Thanks very much. :D
     
  18. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Its a 5.1V zener diode, its optional.

    If you are sure that the Vinp to the PIC's ADC will not exceed over +5V then its not required.

    I second simpler method would be to use a 1K0 resistor in series with OPA Vout and the PIC pin.

    OK.?:)
     
  19. reynn

    reynn New Member

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    ok sir, but didnt you say that this circuit also works with zilog?
     
  20. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    The circuit will amplify the 10mV/Cdeg from a LM35 upto a maximum of +5Vdc.

    Connecting any ADC input that accepts 0V thru +5Vdc will be OK.

    OK.?
     
  21. reynn

    reynn New Member

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    ok thanks sir. :D
     

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