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anemometer interface with AVR

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

  1. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Viz,
    Thanks for the update on the "tranemometers", I could not get them to work reliably in simulation.

    I think 'naz' tried the lamp filament but again it was unpredictable.
    Your heated 'element' looks interesting, I would like to see the final project results, as you say the 2W dissipation is a burden on the supply.

    I did some trials using 1N914 diodes in a bridge configuration, one pair exposed to the 'airflow' and the others shielded, it gave promising results.

    Eric
     
  2. naz83

    naz83 New Member

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    Hi Eric

    Thanks for the file, but the two sensors are pt1000s not ntc, and yes its like having 2 anemometers one subjected to airflow and other at ambience but both are heated since its a ptc when air is blown over 1st pt1000 the voltage drops but since i am using a diff amplifier to subtract the results i see that on blowing air the voltage increases. This is what happened on the breadboard as well but when subjected to a constant stream of air the voltage does increase but then goes back to its original state even with the air stream still on, so i guess something wrong with the circuit.

    and regarding the ltspice no graph, i just opened the file that u sent after unzipping it but on simulation i get the graph window but with no plot on it. i havent changed anything.
     
  3. naz83

    naz83 New Member

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    Hi Viz,

    thanks for your update. i did build the transistor one as well but dint work, even the bulb filament wasnt good, though i got the filament to work as an indicator of air flow but not as an air flow meter, is it possible to display the air flow detector using AVR could u plz brief me on this. and i need to use the principle of hot wire anemometry so cant think of sonic now.

    Thanks for your help.
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    When using LTspice are you selecting RUN and also clicking the point on the circuit that you want to plot.??

    If you dont click on the circuit at the location you want to plot, you will get a blank plot.
    EDIT:
    Unzip this avi file.
     

    Attached Files:

    • naz2.zip
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    Last edited: Aug 13, 2010
  6. Vizier87

    Vizier87 Active Member

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    hot wire anemometry ain't the best if you're looking for durability. My design is pretty simple, just fix a light bulb as close as possible to a temperature sensor (I used an LM35), and light it up. The temperature reading of the LM35 will rise rapidly to around 200-460mV from a still air to a full fan blast (you can easily amplify that later). The air gap between the sensor and the differential heater should be very small, but not touching.

    My research is not so much about what's the best anemometer, but more on how to make the tolerance higher using dimensional designs. I'll update this later.

    Cheers. :)
     
    Last edited: Aug 13, 2010
  7. naz83

    naz83 New Member

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    Thanks Eric, its working now. Did u have a look at the circuit with pt1000s what do you think of it?
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    I will relook at the PT1000 circuit.

    EDIT:
    This is the LTspice version of your PT circuit, it does not work as you expect, unless I missing something.?
     

    Attached Files:

    Last edited: Aug 13, 2010
  9. naz83

    naz83 New Member

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    Eric, i get the error msg cant find ca3140....
     
  10. naz83

    naz83 New Member

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    pt100 asc files

    Hi Eric,

    here are a few models for pt100 that i found, how can i modify them to pt1000.

    Regards
    naz
     

    Attached Files:

  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    Why dont you use a 1000R resistor and step its value parametrically from say 1000R to 1050R in 5R steps.?
    AAesp01.gif

    You could open the PT100.sub with a text editor and change the parameters to suit a PT1000.
    Differencies between PT1000 and PT100

    A PT1000 is however a temperature-dependent resistance. It has 1000 ohms with zero °C, with 1°C 1003.85 ohms with 10°C 1038.5 ohms and so on. The temperature coefficient amounts to depending upon platinum material +3.85 Ohm/°C with the PT1000 and +0.385 Ohm/°C with the PT100. A PT1000 has therefore a larger slope and makes possible thereby a higher resolution. The sensor has small currents, a self-heating of sensors small is minimized. With a PT100 it is easy to develop thermometers for a large temperature range.

    http://www.amplifier.cd/Technische_Berichte/PT100/Temperature_measurement.htm[​IMG]
     
    Last edited: Aug 13, 2010
  12. naz83

    naz83 New Member

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    single self heated thermistor anemometer

    Hello Eric,

    I tried the circuit of this single self heated thermistor today and i also have attached the results obtained.. plz do have a look and tell me as to what you think of the circuit and do u think it works fine... i have used 741 as my opamps...

    Thanks.
     

    Attached Files:

  13. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Downloaded your file, get back to you.

    EDIT:
    Got your circuit loaded into LTspice Sim, can you tell the resistor values and details of the thermistor.?
     
    Last edited: Aug 24, 2010
  14. naz83

    naz83 New Member

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    Hi Eric

    all the bridge resistors are 100ohms and the resiatances from 741s are 1.5k........plz do let me knw wht u think of the circuit... and also plz do send me a copy of the ltspice file too...
    Thanks
     
  15. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi naz,
    This is what I get with LTS using the component values you posted.????
    Can you recheck the component values.
     

    Attached Files:

  16. naz83

    naz83 New Member

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    Hi Eric,
    The thermistor is 1k that i am using, its a bead type thermistor..... and i am seeing the output at pin 6 of the second 741 and grnd... basically across the thermistor.... could u plz help me correct the circuit in some way so that i get the correc result and also i amusing a supply of +5 and -5....
     
  17. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    OK, I was trying it with a single supply!
     
  18. naz83

    naz83 New Member

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    simuation diagram and results plotted

    Hi Eric

    I have attached my simulation results obtained in proteus.. plz do have a look...
     

    Attached Files:

  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    ok, will look it over.

    EDIT:
    I cannot duplicate in LTS what you have posted for Proteus.??
     

    Attached Files:

    • naz5.gif
      naz5.gif
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    Last edited: Aug 25, 2010
  20. naz83

    naz83 New Member

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    Hi Eric

    looking at the circuit and the results i posted to u, wht do u think of the circuit as an anemometer...... when i subjected the thermistor to a steady air flow its voltage increased and remained at that voltege till the air stream was taken off... so it makes me think that this circuit is working fine as an anemometer..... plz comment on it....
     
  21. naz83

    naz83 New Member

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    Hi Eric

    can u plz send me the screen shot of the lts file naz2.asc which had the pt1000s in it as i am not able to open the .asc file that u sent me...

    thnx
     

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