Project help???

Discussion in 'The Projects Forum' started by dogar sahab, Oct 16, 2008.

  1. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    I want to make TEMPERATURE MONITOR UNIT and then its computer interfacing through 8051 microcontroller!!!!
    I am searching for the schematics for this project..I have a schematich which employ op-amplifier but the output wouldnt be able to use it in the microcontroller..!!!
    so what should I do????
    what would u recommend to do???
    I am attaching the schematic too!!!!
    Please help..I am stuck!!??
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    All you need to do is detect the relay contacts closing/opening. That just takes one pin configured as an input.

    Unless you have an "original" 8051, in which case you will need an interface IC like an 8255.
     
  3. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    sorry,i couldnt get it!!!
    would u please elaborate it more comprehensively!!???
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    I can't - I know nothing about your 8051. Is it an Intel 8051, or a second-sourced 8051 that has interfacing built in?
     
  5. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    i have got a microcontroller 8051 which I am sure is not genuine as it is very cheap in my country!!!!u can say half a dollar!!!!
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    If is is a plain 8051, it takes a lot of external hardware to make it work. The obvious thing is a well-regulated power supply.

    The uC also has to have some memory. It is normal to use some RAM for storage, and ROM to hold the program to execute. A special programmer is needed to program the ROM, plus a compiler capable of outputting 8051 code.

    For the outside world, an 8051 also need an inteface chip, like the 8255. One might be able to sense your temperature controller and drive the display.

    There are later developments of 8051's that have all this stuff built in - AVR has a line of them. Then you only need the power supply and the programmer.
     
  7. RiJoRI

    Well-Known Member

    Aug 15, 2007
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    Why would you need an in 8255?

    Anyway, we did a temperature-sensing module a few years ago, and instead of forcing the micro to do the calculations, we used a DS1620 from Dallas Semi (now Maxim). No floating point math, no A/D conversions: just ask the chip "What is the temp?" and read back your value.

    --Rich
     
    Last edited: Oct 17, 2008
  8. karthik_dm

    Member

    Oct 16, 2008
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    -------------------
    i suggest u not to use op-amp..instead use temp.sensor modules like LM35,LM34 which are readily available in markets..u can simply connect their output to microcontroller ports...they are three pin ICs... i think thiz may help u...
     
  9. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    ^this is what exactly i am thinking of doing!!!
    But this is the electronics lab project and we would have to employ any electronics component in it!!!!
     
  10. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    another problem with the op-amplifier is that it will act as comparator and cant give us the range of teperature values!!!
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
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    The 741 is set up as a comparitor, so that is how it behaves. The potentiometer on pin 2 sets the trip point. The circuit is a thermostat. Its only function is to signal that the temperature is above or below the set point.

    Why is this a problem?
     
  12. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    yes this is what I dont want to make..
    I want to MONITOR the temperature...I dont want to fix the temperature....
    So I should use temperature sensor instead, but the problem is with microcontroller...I use sensor first which senses the temperature and its analog output is converted into digital by ADC CIRCUIT and then this output is fed into microcontroller and then the output is displayed on seven segment display!!!
    The problem is with microcontroller...??how to use that and what should be the C CODE???
    any hint????
     
  13. beenthere

    Retired Moderator

    Apr 20, 2004
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    I thought the circuit you posted was the sensor you had to use.

    The fixed resistor and NTC thermistor will work for temperature sensing. You will need an amplifier to increase the voltage by some amount after you determine the operating characteristic.

    Your uC probably has an A to D converter built in. If not, you will need to select one that gives you the resolution you need. Then you will need to decide what kind if interface you want to use to control the A to D.

    The input will be numbers that relate to the temperature. You will have to convert the numbers to engineering units. The thermistor will follow a response curve, so using a lookup table in the uC memory will let you do the conversion and allow for the thermistor's non-linearity.

    Suggested subjects for further study:

    Thermistors
    Analog to digital conversion
    Interfacing
    Microcontrollers, with emphasis on ones that have a C compiler available
     
  14. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    I am using LM35 temperature sensor and its datasheet is available on the first page of this thread!!!
    Analog to digital conversion isnt difficult at all.....
    So the main problem is to write the C code...I also want to tell that I dont have built-in ADC in my AMTEL 8051 MICROCONTROLLER!!!I will have to have external hardware for that...!!
    You guide me what should I keep in my mind while writing the C code i.e time delay etc!!!??
     
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