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anemometer interface with AVR

Thread starter #1
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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ericgibbs

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#2
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
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.?
 
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Thread starter #3
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..........
 

ericgibbs

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#4
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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Thread starter #5
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............
 

ericgibbs

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#6
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............
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.??
 
Thread starter #7
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.
 

ericgibbs

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Most Helpful Member
#8
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.
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.
 
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Thread starter #9
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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Thread starter #11
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
 
Thread starter #12
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
 

ericgibbs

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Most Helpful Member
#13
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
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.
 
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Thread starter #14
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
 

ericgibbs

Well-Known Member
Most Helpful Member
#15
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
hi naz,
Please answer my question...
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.
Which type is it.?:)
 
Thread starter #16
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...................
 
Thread starter #17
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
 

ericgibbs

Well-Known Member
Most Helpful Member
#18
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
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.
 
Thread starter #19
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
 

ericgibbs

Well-Known Member
Most Helpful Member
#20
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
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.
 
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