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anemometer interface with AVR

Discussion in 'AVR' started by naz83, Jul 13, 2010.

  1. naz83

    naz83 New Member

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    hI ALL.
    I HAVE MADE AN ANEMOMETER USING THE BULB FILAMENT BUT I WANT TO CONVERT IT TO DIGITAL AND THEN USE AN AVR TO DISPLAY THE READINGS, I HAVAENT USED AN AVR BEFORE SO PLZ HELP.. THE CIRCUIT DIAGRAM IS ATTACHED AND THE VOUT GENERATED IS FROM 1.63V TO -2.93V.....

    COULD ANY1 PLZ SUGGEST HOW TO DO ADC AND ALSO HOW DO I PROGRAM AN AVR..... I HAVE DONE ALP FOR 8051,8086 AND 8085

    THANKS
     

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  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Where are you measuring Vout on your circuit in order to get 1.63V TO -2.93V.

    EDIT: and what are the device type numbers.?
     
    Last edited: Jul 13, 2010
  3. naz83

    naz83 New Member

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    device numbers

    R1 1 100 Ohm 1/4W Resistor
    R2 1 470 Ohm 1/4W Resistor
    R3 1 10k 1/4W Resistor
    R4 1 100K 1/4W Resistor
    R5 1 1K 1/4W Resistor
    C1 1 47uF Electrolytic Capacitor
    U1 1 78L05 Voltage Regulator
    U2 1 LM339 Op Amp

    sorry for using capitals.............

    i measured the voltage across the led............ the led glows on adjustiing the pot and at ambience ie no air flow, when air is blown it goes off.......... depending on the amount of air flow the voltage drops across the led acoordingly..........
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    Look at this image I have added a voltmeter to show where you should measure the voltage output.
    If you measure directly across the LED it will always read the same voltage.???

    EDIT:
    Added the components to your circuit.
    BTW: a LM339 is a comparator not an OPA..
     

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    Last edited: Jul 13, 2010
  6. naz83

    naz83 New Member

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    Adc

    thanks,
    I will try this circuit and measure the voltage....... can u plz tell me as to how to do the linearisation, scaling etc..... which ADC should i use and how do i interface using an AVR to display the measurements............
     
  7. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    I can help with the analog scaling etc, but I use PIC micro controllers and program using assembler.
    Other members are more conversant with AVR's and their coding.

    I would suggest you determine the voltages you can get from the LM339 output.
    As its wired at the moment all you will read is high or low depending upon the setting of that pot.??
     
  8. naz83

    naz83 New Member

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    caliberation

    hi thnx for the reply........

    could u tell me as to how to caliberate the circuit and how should i blow air over it whose speed is known..

    and how do i calculate the output voltage range and also the high and low voltages.
     
  9. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    Where did you get the circuit from.?
    All it will output is 0V or 12V, depending upon the resistance of the lamp filament at one temperature.
    The only way to make it work would be to calibrate the 100K pot setting, so it is not really suitable for an ADC input.
     
    Last edited: Jul 13, 2010
  10. naz83

    naz83 New Member

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    air flow detector

    hi eric...

    what do i need to do inorder to make it work as an air flow detector.. do you have any circuit that works like a hot wire anemometer..... i tried another using thermistors but dint get any output really.... i will attach that pic as well.......... plz do post any circuit if you have...

    in the thermistor pic i have used 100k thermistor instead of 50k and 1k thermistor instead of 2k..... but i did not get any voltage as expected...plz help

    thanks.
     

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  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    Last edited: Jul 14, 2010
  12. naz83

    naz83 New Member

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    sensitive air flow monitor

    Hi eric,

    The aim of this project is to develop a simple sensitive air flow monitor using thermal sensing. A voltage output from the electronics can be converted to digital form and displayed using an AVR microcontroller board.
    its something like draught detection....

    thanks
     
  13. naz83

    naz83 New Member

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    transistor anemometer

    eric,

    i tried building the circuit of anemometr using transistors of which u sent the link.. but i dint have 2n4401 so i used bc337 and instead of 2n3904 i used 2n2222........ and instead of LT1013 i used a quad ic lm358... and also the resistance values were not exact but i dint find any change in output, it was a standard 0.8v even after i blew air over it and the transistors were not getting heated at any turn of the pot...

    i am confused as to what needs to be done as most of them sugest that the bulb filament is a good sensor compared to transistors or thermistors.... i don have much time as i need to finalise the circuit and also then move on with the ADC and then AVR part of it.... plz help

    thanks
     
  14. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    If it is a simple airflow detector [draught] , not airflow rate, I would use thermistors with a LM393 comparator that would give a high voltage when air is flowing and a low when no air flow.
     
    Last edited: Jul 14, 2010
  15. naz83

    naz83 New Member

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    hi eric,
    can u give me the circuit diagram for the same as the circuit that i used dint work and also i only have 100k and 1k resistors....

    thnx
     
  16. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    Please answer my question...
    Which type is it.?:)
     
  17. naz83

    naz83 New Member

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    low volocity air flow meter

    hi eric,

    its a low velocity air flow meter that displays air speed... so that i can do linearisation and scaling later to display using AVR...................
     
  18. naz83

    naz83 New Member

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    hi,

    can u plz tell me if this type of circuit can be simulated on proteus and find out if its working? and also can u plz give me the circuit of a low velocity air flow meter that displays air speed for further lineariation and the AVR interface

    thanks
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    I tried to simulate this transistor anemometer using LTspice, but I could not get it to work.
    I understand from some members who have built it, say it works OK, others say it dosn't.???

    Why not build the circuit using the nearest equivalent transistors and see how it works for you.
     
  20. naz83

    naz83 New Member

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    transistor anemometer

    hi eric,

    i did build the circuit on a bread board using components but it dint work, however i dint get the exact transistors so i used bc337 and 2n2222 instead.

    if i build this circuit in software how do i test it , if its working......... manually i would just blow air over the circuit to see if its working but how do i do it in software?.....

    thnx
     
  21. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    Since my last post I have been retrying to simulate the circuit, but with no success, I will keep trying.

    EDIT:
    The BC337's should work OK.
     
    Last edited: Jul 15, 2010

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