Air Flow Detector Circuit. - Electronic Circuits and Diagram-Electronics Projects and Design

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Air flow detector circuit. admin June - 7 - 2008 117 Comments Description. This circuit can give a visual indication of the rate of air flow.It can be also used to check whether there is air flow in a given space. The filament of a incandescent bulb is the sensing part of the circuit.When there is no air flow the resistance of the filament will be low.When there is air flow the resistance drops , because the moving air will remove some of the heat generated in the filament.This variations in the resistance will produce variation of voltage across the filament.These variations will be picked up by the opamp (LM339) and the brightness of the LED at its output will be varied proportionally to the airflow. Circuit diagram with Parts list.

Notes. The filament L1 can be made by removing the glass of a 40W incandescent bulb. The circuit can be powered from a 12 V DC power supply.

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117 Responses to “Air flow detector circuit.” rajeevkumar says: June 20, 2013 at 5:15 am sir the result is coming oppositely to ur saying.when air flows through the filament the brightness of bulb is decreasing Reply Seetharaman says: April 28, 2013 at 8:16 am Hi Adnan you have to use low ohmic PTC (33 ohms). LM339 can drive a maximum of 6mA, hence you have to add a transistor to take care of the drive current of the relay. Reply ADNAN says: April 26, 2013 at 12:36 pm

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Hi sir. Can i use any thermistor or air sensor instead of L1 filament? if yes, kindly suggest which sensor or thermistor can be used. Moreover, can i directly operate the relay at the output pin #2 of LM339? Looking for your kind reply. Reply nidhi says: April 24, 2013 at 7:50 am plzzzzz tell me that where it is used Reply duncan says: April 15, 2013 at 11:51 am hi sir, help send me a report on airflow because am interested in doing this project but i have litle knowledge. thank you Reply Seetharaman says: April 16, 2013 at 9:43 am Air flow detector is user to find the adequate air flow in a system. (may be a bower or a cooling fan air flow) Here the positive temperatue coefficient charecterestic of the bulb filament is used for detecting the air flow(the air flow will cool the bulb filament (which is heated by constant current flow through it). Once the air flow decreases the bulb temperature will increase its resistance will increase which will detected and indicated by the LED. Reply Reply Anmol says: April 17, 2013 at 5:44 am sir, I am making this project in my college and i am required to submit the report but due to lack of adequate information i am unable to make the report. so kindly help me by providing some more information on this topic or your report on this project. Thankyou. Reply Anmol says: April 14, 2013 at 8:45 pm Hi Sir, i am doing a project on air flow detector and i have to submit a report on that but i dont have enough information to make the report. So i request you to give some more information about the project or post your own report.It would be of great help for us.Thankyou. Reply Tahsinur Rahman says: March 30, 2013 at 10:25 pm Hi,sir i want to know measure the rate of air flow..How i can improve that..pls reply… Reply vivesh says: March 23, 2013 at 5:43 am can you explain npn transistor and how wor Reply J.Hepzibah beulah says:

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March 15, 2013 at 4:39 am Hai sir, i want to know the complete info that how much amount of air this circuit detects. and added that what is the replacement for filament in this circuit. how can i enhance this circuit in real time applications. ive chosen this as my mini project in this sem . so please send all these informations to my mail soon. thank u very much Reply fad says: March 13, 2013 at 8:38 pm name of connection of the resistors…? Reply dips says: March 13, 2013 at 6:51 pm what is the function of each resistance and the function of the capacitor?pls help Reply nagaraj says: February 28, 2013 at 7:00 am can u give me the detail information about application of air flow detector and where it is mainly used………..? plz give me the answer,im doing mini project on this topic sir………. sir,any other circuit is previously used for air flow detection? if its used, can u send circuit diagram and drawback for that circuit sir…………. Reply vishwanath kharabe says: February 27, 2013 at 12:15 am fine it’s good one &easier Reply nagaraj says: February 26, 2013 at 5:50 am sir,any other circuit is previously used for air flow detection? if its used, can u send circuit diagram and drawback for that circuit sir…………. Reply nagaraj says: February 26, 2013 at 5:30 am can u give me the detail information about application of air flow detector and where it is mainly used………..? plz give me the answer,im doing mini project on this topic sir………. Reply ganesh says: February 22, 2013 at 1:23 am air flow Reply gaurav says: February 18, 2013 at 1:01 am sir i would like to know the function of the resistor R4.. is it a potentiometer?

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Reply sudan says: February 11, 2013 at 7:10 am hi sir.can u give us the information about working principle Reply Seetharaman says: March 16, 2013 at 8:15 am Hi Please go through my 31st October comment Reply Aadil says: February 5, 2013 at 10:42 am Hi sir i wanna work on this project as my miniproject so pls give me an idea about its expenses Reply Engr Adnan says: March 13, 2013 at 7:50 am Salam,, dear Aadil, its very cheap project..About PKR.500.. If u want to learn, don’t see expenses..or work in group.. Reply gaurav says: February 4, 2013 at 1:05 am hello sir, i am gaurav, I am studying 3rd yr(Extc).i am doimg my miniproject on dis air flow dedector topic. sir i want to know more details about this project.i am very eager to know dis.so please send me more information about (principle,construction,each elements work) to my mail ID..thank u sir…. Reply HARISH says: January 30, 2013 at 11:51 pm anyone send airflow detector final documentation. Reply Debasis Singha says: December 24, 2012 at 8:12 am Please give me a detail description and corresponding circuit diagram of about— a man or any object when enter into a room light/lights automatically switch on. Reply Aliya says: December 23, 2012 at 8:52 pm May i know the practical apps of this?? Reply haimobati says: December 22, 2012 at 11:42 pm plz send me more detail about this project. Reply

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PATL UV says: October 26, 2012 at 2:36 am SIR ; WHAT IS ADVANTAGE & DISADVANTAGE OF AIR FLOW DETECTOR? HOW IT WORK? PLS REPLY FAST Reply seetharaman says: October 31, 2012 at 6:10 am Air flow detector is user to find the adequate air flow in a system. (may be a bower or a cooling fan air flow) Here the positive temperatue coefficient charecterestic of the bulb filament is used for detecting the air flow(the air flow will cool the bulb filament (which is heated by constant current flow through it). Once the air flow decreases the bulb temperature will increase its resistance will increase which will detected and indicated by the LED. Reply patel uv says: November 5, 2012 at 8:57 am thanx sir thank you very much Reply shwetha says: September 26, 2012 at 2:06 am plz some info about dis…. Reply ABHISHEK says: September 20, 2012 at 1:19 am plz send me more detail of this project. Reply Rupa says: September 20, 2012 at 12:34 am How can I connect the filament in the bread board? Plz explain… It;s often getting damaged.. Reply seetharaman says: September 20, 2012 at 9:37 am Hi Rupa use a bulb and solder it through wires to bread board. (use a 12volt mini lamp used in car dash board) Reply niki says: October 31, 2012 at 9:24 am hi sir as i have got to do miniproject to design an experiment for an apllication involving minimum of 1 digital and analog unit it .i am full too confused please help me Reply chaitu svsk says: September 13, 2012 at 5:49 am please do explain the working of each component in air flow detector ckt… its very urgent…..Please mail me as early as possible..

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Reply Seetharaman says: September 14, 2012 at 4:42 am Hi Please go through my earlier comment March 21, 2010 at 9:54 pm Hi Ireti The IC 7805 forms a 60mA constant current source feeding the filament. The voltage drop across it is compared by the comparator IC and the ouput is produced. Normally cold bulb filament resistance is low(a positive temperature coefficient material) as it gets heated up the drop across the filament increases due to which the LED goes on. when the filament senses air flow the heat is removed hence the resistance falls down, due to which the LED goes off. If you want the operation other way, air more than a particular flow to indicate by LED going on, interchange comparator ICs inv and non inv port (4 & 5) Reply NIKHIL says: September 12, 2012 at 5:59 am Sir, will you plzz tell me from where i can get the filament or any other component can can i use other than filament??? plz sir reply me as soon as possible!!! Reply Ayesha says: September 9, 2012 at 7:30 am hello sir, I am Ayesha.I am studying 3rd yr(ECE).i am doimg my miniproject on dis air flow dedector topic. sir i want to know more details about this project.i am very eager to know dis.so please send me more information about (principle,construction,each elements work) to my mail ID..thank u sir…. Reply sajith says: September 2, 2012 at 1:27 am it is very essential for young talented guys Reply sir m neeraj...sir please send me aplication of this project...plz sir rply soon... says: August 30, 2012 at 4:17 pm sir m neeraj…plz send me aplication of this project…rply soon… Reply priya says: August 25, 2012 at 5:06 am here what is the purpose of ic7805 and r4 is a variable resistor ? Reply shoair says: November 1, 2012 at 9:19 am lm7805 is voltage regulator ic, means it can give you only 5 volt dc only.. wel i dn’t think r4 is variable resistor it’s not the symbol of variable resistor.. Reply archu says: August 25, 2012 at 5:04 am

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what is the purpose of Ic7805 anf is r4 is a variable resistor? Reply priya says: August 23, 2012 at 6:48 am helo sir, i am doing the same circuit in bread board. i learned from your previous comments that the filament has to be completly removed and soldered but for bread board circuit how should i connect the filament? plz do help me with positive replies Reply shweta gupta says: August 14, 2012 at 9:51 pm sr plz send me more information about air flow detector Reply D Suseendrakumar says: July 21, 2012 at 8:51 pm Sir, I’m Suseendrakumar doing my engineering course in Madras institute of technology. Can you pls tell the circuitry to connect the output to the air flow meter so as to measure the air flow? Reply esa saveme edwin says: June 27, 2012 at 4:23 am Hi Sir/Madam i am a student of Nigeria Naval Engineering College Sapele and i’m doing a project on this topic air flow detector(design and construction of air flow detector)and this information is very useful to me. so, i request you to please send me more information about this topic to my mail id. Thank you Sir/Madam Reply dops says: July 25, 2012 at 9:07 pm what kind of variable resistor should i use?please help:( Reply jansi says: August 3, 2012 at 10:27 pm hello sir, I am jansi.I am studying 3rd yr(ECE).i m doimg my miniproject on dis air flow dedector topic.sir i want to know more details about this project.i am very eager to know dis.so please send me more information about (principle,construction,each elements work) to my mail ID..thank u sir…. Reply Seetharaman says: June 26, 2012 at 9:48 am Hi Can be used to detect the cooling air flow is sufficient, indicating cooling system is functioning. Can also be used for measuring velocity of moving object > or < than the specified value. you may also go through sept 2nd comment. Reply venky says: June 25, 2012 at 11:57 pm

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sir I want the applications for air flow detector Reply k.anil varma says: May 18, 2012 at 1:15 am please provide the detail information about this experiment and also tel the working and application of this experiment. Reply chinmay says: April 1, 2012 at 2:28 am please provide the detail information about this experiment and also tel the working and application of this experiment Reply ankit panjwani says: March 29, 2012 at 10:34 pm sir, sir can u please send me the internal layout of the connections of this circuit so that i can make a pcb for this circuit. i also want the list of applications about this circuit, or where this circuit is used. Reply Deepak Mulewa says: August 16, 2012 at 8:39 am Sir, will you plzz tell me from where i can get the filament or any other component can can i use other than filament??? plz sir reply me as soon as possible!!!!! Reply Jaack says: March 28, 2012 at 1:42 am aneesh m calicut the air flow circuit can be used in Heating Vent AirCconditioning, detecting movement of cargo, parts, people, animals. Automobile cooling, combustion etc. Whenever you want to detect absence or presence of a gas. Air is just one could be exhaust if cool enough avoid corrosive gases in detector circuit. Do NOT use to detect flammable or explosive gases! Reply phangsh says: March 26, 2012 at 6:52 am Hi.I’m working for my project using this circuit. May I know what are the functions of all those components used for this circuit? Especially for resistors and capacitors. Please reply me as soon as possible. I’ll be very grateful for your help. Reply aneesh m calicut says: March 22, 2012 at 6:46 am sir, sir, i am studying 4th semester B.tech(ece)in MG university, and i m doing mini project on this air flow detector and this information is very useful to me.So, i request you to please send me more information and where the air flow detector is used(list the applications)? about this topic to my mail id. Reply

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vimala says: March 13, 2012 at 12:57 am Hi sir, i am studying 2rd B.tech(ece), and i m doing mini project on this air flow detector and this information is very useful to me.So, i request you to please send me more information about this topic to my mail id. Thank You. Reply rama says: February 22, 2012 at 6:51 am Hi sir/madam, i am studying 3rd B.tech(ece), and i m doing mini project on this air flow detector and this information is very useful to me.So, i request you to please send me more information about this topic to my mail id. Thank You. Reply avaneesh says: January 30, 2012 at 11:46 pm Hi sir, I am student in University of pune, i am studying in B.E.(electronics) ,if you can give more information about the rest of the circuit, the function of each resistance, and the function of the capacitor, and if there any hints or notes, because iam trying to make a project semilar to this one. You can send them to me by an email. and any modification pls suggest me Thank you. and any project on temperature sensor . Reply vigneshwar says: January 28, 2012 at 6:40 am where the air flow detector is used(list the applications)? Reply Min says: December 17, 2011 at 11:42 pm hello sir, its me again. I’m sorry if I asked to much but is it possibly for you to share with me the picture of the circuit? Reply seetharaman says: December 16, 2011 at 12:13 pm Hi Min Tungsten has got a good Positive temperature coefficient (alpha) and will not get oxidized easily hence it is preferred. Reply Min says: December 15, 2011 at 9:40 pm Thanks, but one more question, I can just do it without the tungstan wire right?? Reply Seetharaman says: December 15, 2011 at 9:40 am Hi Min please refer to 26th Oct comment. Reply Min says:

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December 14, 2011 at 10:30 pm I am doing this circuit for my project but It doesn’t work. I really want to do this for my project. My only problem is the Filament, I still don’t know how to connect the filament to the board for testing. Please help me. Reply Shalini says: October 26, 2011 at 9:50 am i’ll try that sir

thanks a lot for your prompt and positive replies!

Reply seetharaman says: October 26, 2011 at 9:38 am Hi Shalini you can use it as it is but it will be bulky you carefully remove the filament including its end connecting stiff wire, and solder the filament through the stiff wire to a small pcb (a standard straight line one or a dotted one – veroboard). now your sensor is ready for use. infact you require a tungstan wire which has a good positive temperature coefficient, which is more suited for the project. since you do not get them freely in the market the simple above procedure is given. you can use a small radio bulb(as small as possible so that it can sense the temperature change big bulbs will take a loger time as they have inert gas filled in, 6 volt 300mA bulb) without breaking it. Reply Shalini says: October 26, 2011 at 1:04 am Thanks a lot sir! But how do i connect the filament in the circuit. Pls help cause i’m pretty clueless about how to do it. After breaking the glass, how do I connect it in the circuit? Only the glass needs to be broken? not the other bulb attachments like the base also? Reply seetharaman says: October 25, 2011 at 4:37 pm Hi Shalini you can use the 40watt bulb filament by carefully breaking the glass. this can be best done by keeping the bulb in a thick plastic cover and carefully giving a hit with a sharp tool. now carefully take out the filament and use it. the pot is for the flow level set adjustment. LED will come on when air flow sets in. to ckeck the operation first without any air flow adjust the pot such that the LED just goes off. now slowly bolw air on the filament the LED will come on, indicating the circuit is functioning. Reply Shalini says: October 23, 2011 at 7:01 am Sir, also how do I use the filament specified in the given circuit? It’ll work properly no? I’m relying on it for my project. So awaiting a positive reply… Reply Shalini says: October 23, 2011 at 6:59 am Sir, what is the purpose of the var. resistor (100k – R4)? what resistance do we have to set it to while monitoring the air flow? Pls reply asap… doing a project that needs to be submitted in the next 4 days Reply Harison says: August 8, 2011 at 4:31 am Its a nice work am also doing a project work on the air flow detector. pls if you can send its design to me thanks.

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Reply samson Awaje says: August 8, 2011 at 4:26 am Sir, please i may also need its application and significance thanks. Reply samson says: August 8, 2011 at 4:24 am Hi, Its a nice work. am also doing a project work on air flow detector. Please if you could help me with its design. Reply hemant tewatia says: July 18, 2011 at 11:11 pm sir,can u tell, what improvement we done in air flow detector any addition can we done??? Reply priya says: June 27, 2011 at 1:15 am please do explain the working of each component in air flow detector ckt…the connection is simple n works really good….please send the information to my mail…. Reply ankit rathore says: February 8, 2011 at 9:48 am actually i want to make air flow detector as my minor project so can u plz provide me PCB arrangement for this;; Reply M.SHIRISHA says: December 15, 2010 at 7:40 am also explain in detail about application in boiler furnace Reply M.SHIRISHA says: December 15, 2010 at 7:39 am can u list any other industrial applications of the circuit……..we are asked to give industrial applications Reply M.SHIRISHA says: December 15, 2010 at 7:38 am sir can explain in detail about application of air flow detector in boilerfurnace………… can u list any other industrial applications of the circuit……..we are asked to give industrial applications Reply M.SHIRISHA says: December 15, 2010 at 7:34 am Thanks a lot for ur response…. i got output for the circuit ………but filament is very sensitive it is easily getting damaged…….can u suggest any other component in the place of filament …… Reply

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fozia says: October 24, 2010 at 8:24 pm You can send them to me by an email. Thank you Reply fozia says: October 24, 2010 at 8:22 pm hi sir The project seems to be quite interesting and I would surely try this project this semester.Could you please explain me the project in a bit more details. If you can give more information about all the componantst, the function of each resistance, and the function of the capacitor, and if there any hints or notes,& how it works with datasheets. Reply selorm agbo says: October 6, 2010 at 2:21 am I am student in knust, iam studying biomedical engineering,if you can give more information about the rest of the circuit, the function of each resistance, and the function of the capacitor, and if there any hints or notes, because iam trying to make a project semilar to this one. You can send them to me by an email. Thank you Reply mc says: September 13, 2010 at 10:00 am hi sir.. may you pls help us upgade ths circuit by putting different levels of required air flow Reply seetharaman says: September 8, 2010 at 12:01 am Any low noise operational amplifier will do to give the required gain and off set. 725, 308, 071, 3140 etc. the output of this ic can be fed to a 3 1/2 digital display normally comes with 0 to 200mV DC FS. Reply sus says: September 7, 2010 at 10:05 am can i please know which ic an i use to get the analog out put from the filament to be converted to a binary digital output or directly to 7 seg display. Reply seetharaman says: September 2, 2010 at 9:16 am Hi SHIRISHA practical application in boiler furnace air flow measurement, will enable total combustion of oil, coal or gas. air flow measurement through any air duct. for temperature and pressure measurement you have to add suitable sensors like RTD pressure transducer etc. to add digital indication you can use the analog value availabe at the filament through amplification, can be calibrated to velocity of air flow by comparison Reply shirisha says: September 2, 2010 at 8:29 am

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Thanks for ur response sir ……. can u give practical applications of this circuit in industries……….. i also want to extend this project….like i want to include numerical indication of air flow level…. can include any other circuit to detect temperature or pressure in this can you send me circut Reply seetharaman says: August 25, 2010 at 10:07 am Hi Shirisha please go through my march12th comment, that will give you the idea on the principle of operation. air flow meters are of different type. measurement with rotating vane speed is anemometer, and hot filament type is the above one. both are fairly accurate if properly calibrated. Reply shirisha says: August 24, 2010 at 10:23 pm i also want to extend this project….like i want to include numerical indication of air flow level…. can include any other circuit to detect temperature or pressure in this can you send me circut Reply shirisha says: August 24, 2010 at 10:19 pm sir can i also know about application of this projec in industry ….more over how this instrument is different form other air flow detectors….i also need advantages,disadvantages and precaution to be taken… dont mind please answer to my questions Reply shirisha says: August 24, 2010 at 10:00 pm hello sir i am shirisha from gnits……i am doing mini project on air flow detector …….i need complete information about working of this circuit and funtioning of each componenent placed …… Reply seetharaman says: June 26, 2010 at 10:16 pm Hi Rupak the standard method is to use a rotating blade anemometer. this uses the principle of cooling due to air flow on a heated wire. as the air flow increases the cooling is greater. as it is a matalic wire with positive resistance temperature coefficient the value of resistance of the filament (sensor) is measured to indicate the flow. Reply Rupak says: June 26, 2010 at 1:09 pm sir, the project seems to be quite interesting and I would surely try this project this year.Could you please explain me the project in a bit more details Reply adeel says: April 18, 2010 at 3:10 am thanx for giving the information of this project… Sir…! we are doing a project on air-flow detector…and we need to demonstrate and give the presentation to our Externals in the University…

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so pls provide me the complete informations about the project with diagram & the picture of this project Air Flow Detector…! Thanx… Reply seetharaman says: March 21, 2010 at 9:54 pm Hi Ireti The IC 7805 forms a 60mA constant current source feeding the filament. The voltage drop across it is compared by the comparator IC and the ouput is produced. Normally cold bulb filament resistance is low(a positive temperature coefficient material) as it gets heated up the drop across the filament increases due to which the LED goes on. when the filament senses air flow the heat is removed hence the resistance falls down, due to which the LED goes off. If you want the operation other way, air more than a particular flow to indicate by LED going on, interchange comparator ICs inv and non inv port (4 & 5) Reply ireti says: March 21, 2010 at 1:10 pm Hi sir, I am student in oou ago iwoye ogun state Nigeria, i am studying physics with electronics ,if you can give more information about this air flow detector circuit, the function of each resistance, and the function of the capacitor, and if there any hints or notes, because am to make a project on it. You can send them to me by an email. Thank you Reply shashidhar h says: March 19, 2010 at 4:46 am what is the need of IC7805 in this circuit? Reply vishal says: March 5, 2010 at 5:55 am sir i want to know whether this circuit can also indicate the direction in which air flows? Reply eyesheild says: February 11, 2010 at 12:57 am hi sir thanks to all give for information Reply Ashwini says: January 29, 2010 at 6:56 am What is the output voltage of this circuit? Reply Seetharaman says: January 16, 2010 at 9:30 pm Hallo Usama and Manish IC1 is a constant current source of 60mA for the filament. IC2 is a comparator. With the present circuit the LED will become dim with higher air flow. To make it brighter with higher air flow interchange inv and non-inv inputs of IC2. or alternately return the LED to ground instead of plus 12Volt. IC2 can be replaced with TL071. Happy assembling and enjoy Reply John says:

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November 18, 2009 at 12:09 am This is a simple but useful circuit, thanks for making it freely available. That said I expected the circuit to function in reverse, instead of the LED dimming when airflow is detected I assumed it would brighten. Any suggestions on how to modify the circuit so that the LED brightens with air movement? I tried reversing the input signal to the comparator and it does work but the output barely lights the LED. Reply usama says: November 9, 2009 at 2:37 am i want the simple diagram of this circuit will you give mee plzz?? Reply manish gaur says: August 22, 2009 at 1:01 am hello, give me some more information about this project Reply gurmeet says: August 18, 2009 at 5:45 am pls sir/madam….!! we are doin a project on air-flow detector!! and we need to give a good presentation to our teachers….!! so pls provide me with the informations about the project!! Reply admin says: August 18, 2009 at 10:43 pm I think this wind meter circuit http://www.circuitstoday.com/wind-meter is better for a project. Reply akshatha says: August 12, 2009 at 2:12 am pls sir/madam….!! we are doin a project on air-flow detector!! and we need to give a good presentation to our teachers….!! so pls provide me with the informations about the project!! Reply solomon says: June 22, 2009 at 10:19 am it is good for air flow sensor and i says thanks more on your advice Reply kbrom says: May 31, 2009 at 9:54 pm project for air flow detector &the fuction of each components & how it works with datasheets Reply Mohamed Anany says: January 22, 2009 at 11:19 pm Hi sir, I am student in Cape Breton University, iam studying electronics and control systems,if you can give more

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information about the rest of the circuit, the function of each resistance, and the function of the capacitor, and if there any hints or notes, because iam trying to make a project semilar to this one. You can send them to me by an email. Thank you Reply Brighton Zibengwa says: June 14, 2008 at 6:38 am inclusion of track lay-out will b greatly appreciated by students aspecially. those who take electronics as a hobby Reply

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