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    This handy mobile bug or cell phone detector, pocket-size mobile transmission detector or sniffer can sense the presence of an activated mobile cellphone from a distance of one and-a-half metres. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorised video transmission.

    The circuit can detect both the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode. The moment the bug detects RF transmission signal from an activated mobile phone, it starts sounding a beep alarm and the LED blinks. The alarm continues until the signal transmission ceases.

    Cell Phone Detector Circuit Schematic

    mobile bug cellphone detector

    An ordinary RF detector using tuned LC circuits is not suitable for detecting signals in the GHz frequency band used in mobile phones. The transmission frequency of mobile phones ranges from 0.9 to 3 GHz with a wavelength of 3.3 to 10 cm. So a circuit detecting gigahertz signals is required for a mobile bug.

    Here the circuit uses a 0.22μF disk capacitor (C3) to capture the RF signals from the mobile phone. The lead length of the capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. The disk capacitor along with the leads acts as a small gigahertz loop antenna to collect the RF signals from the mobile phone.

    and another video from Sufyan Ghori

    Op-amp IC CA3130 (IC1) is used in the circuit as a current-to-voltage converter with capacitor C3 connected between its inverting and non-inverting inputs. It is a CMOS version using gate-protected p-channel MOSFET transistors in the input to provide very high input impedance, very low input current and very high speed of performance. The output CMOS transistor is capable of swinging the output voltage to within 10 mV of either supply voltage terminal.

    Capacitor C3 in conjunction with the lead inductance acts as a transmission line that intercepts the signals from the mobile phone. This capacitor creates a field, stores energy and transfers the stored energy in the form of minute current to the inputs of IC1. This will upset the balanced input of IC1 and convert the current into the corresponding output voltage.

    Capacitor C4 along with high-value resistor R1 keeps the non-inverting input stable for easy swing of the output to high state. Resistor R2 provides the discharge path for capacitor C4. Feedback resistor R3 makes the inverting input high when the output becomes high. Capacitor C5 (47pF) is connected across ‘strobe’ (pin 8) and ‘null’ inputs (pin 1) of IC1 for phase compensation and gain control to optimise the frequency response.

    When the cell phone detector signal is detected by C3, the output of IC1 becomes high and low alternately according to the frequency of the signal as indicated by LED1. This triggers monostable timer IC2 through capacitor C7. Capacitor C6 maintains the base bias of transistor T1 for fast switching action. The low-value timing components R6 and C9 produce very short time delay to avoid audio nuisance.

    Assemble the cell phone detector circuit on a general purpose PCB as compact as possible and enclose in a small box like junk mobile case. As mentioned earlier, capacitor C3 should have a lead length of 18 mm with lead spacing of 8 mm. Carefully solder the capacitor in standing position with equal spacing of the leads. The response can be optimised by trimming the lead length of C3 for the desired frequency. You may use a short telescopic type antenna.
    Use the miniature 12V battery of a remote control and a small buzzer to make the gadget pocket-size. The unit will give the warning indication if someone uses mobile phone within a radius of 1.5 meters.

    ask a question

    271 Responses to "Cell Phone Detector aka Mobile Bug"

    1. i tried out this circuit,but it works only for 50 cms or less.have any suggestions for the improvement of the circuit????

      • vivekchandra says: on March 20, 2014 at 4:51 pm

        hi my self vivek i did this project yes it works based on your spending money on project if u want to work it for long distance u should increase your components frequency in this project

      • Hi I completed this project on pcb but its not working, I tried with 9 volts power supply, cam anyone tell mw , what will be the problume, pl contact me my e mail.
        Ramesh k. Psndey

      • Inder says: on May 3, 2014 at 5:57 pm

        hello hell boy, in my circuit buzzer and led gets ON even if no mobile signal is detected can u solve my problem pls…..
        thanks in advance….

      • sir,capacitor spacing also varies or not

      • Kumar VARMA says: on September 7, 2014 at 4:31 pm

        heyy…this is KUMAR VARMA….and even i am having the same problem with this mobile detector circuit……did your problem get solved????if your problem got solved….can you please tell me the solution for that problem…?

      • Kumar VARMA says: on September 7, 2014 at 4:33 pm

        in my circuit buzzer and led gets ON even if no mobile signal is detected can u solve my problem pls…

      • Pls this cct isn’t working for me at all.
        the LED switch on if battery polarity is interchanged but doesn’t detect anything. Otherwise, nothing happens at all.
        Kindly advice, what can i do to get this resolved?

      • mehak mansoor says: on March 14, 2015 at 8:52 pm

        Is your problem solved?

      • Cyber Warrior says: on January 24, 2016 at 7:12 am

        Yup It Can Resolve By Using Managable Adapter.It is an adapter where we can set different different voltage level.Cost is 50-60Rs

    2. I did the circuit for my project, it worked! mine can detected about 9 feet. But 12V voltage make the circuit become too sensitive, it will trigger even if you switch on your room lamp, so I reduce the voltage to 9V and it work fine! I built it on the PCB.

      But remember to insulate the antenna, I used the middle part of TV antenna’s cable – the white one with insulation.

      Actually the circuit is taken from Electronic For You Magazine from India..

      Bye from Malaysia….

      • hi Faudzee,
        I tried this circuit. But it wont work for me.. I think the problem is present in the capacitor. Please give me some comments about the capacitor

      • Harshal says: on April 8, 2009 at 5:06 pm

        i designed d same circuit
        it worked but range is too small, it’s only 15 cm.
        what should be done to increase it..

        can ny1 pls tell me detaled working f d ckt along with purpose f each component and design steps 4 same.

        I need 2 prepare project report so plz help..

        otherwise atleast tell me source whr i can get more details @ same ckt.

        w8ng 4 rply…
        hv a gr8 dy byeeeeeeee

      • hey faudzee….can u mail me all d requirmnts documentation!!…lyk wat kinda capacitors 2 b used preferable…and all oder things…
        i will b highly obliged if u do!!…thank u

      • can anyone pls mail me the details for this cell phn detector i want to increase the range my email id is amritaguha15@gmail.com

      • okello says: on May 28, 2014 at 9:35 am

        how please

      • okello says: on May 28, 2014 at 9:36 am

        tell me how please

      • can u pls send me the circuit.. and will it work with the breadboard???

      • hi this is Aditya. i have seen your comment in one of web page about mobile detector circuit. if u don’t mind can you please send me the details of that mobile detector project..
        thank you.

      • @Faudzee did you use exactly same components given here for your circuit? what type of antenna did you use? can you give me any pic of your ckt?
        i’v also assembled the ckt but range is too small. i guess the problem is in antenna. i need to increase the range. pls help me. its urgent. if u support i will be too benefited.

      • can u plz tell me all the details of this project.. how did u made this? nd how u increased the range upto 9 feet.

    3. hello!
      i am ajendra and i work on this program with my friend jaydeep we compleat this program.it is very easy to make
      my contect no. is +91 *9426318602
      by!by!by! friend!

      • hi..
        i have done all circuitary with 10 volt battery…buzzer beeps even no transmission is there or cell phones r switched off….led flashes on switching on power ….can u help me out with this trouble????
        ……contact me at vand.gupta089@gmail.com

      • what antenna used? please give picture of antrenna.

      • PRIYANKA says: on March 25, 2014 at 10:41 am

        hello, i m priyanka and i am working on this project on PCB can u tell me the capacitors used in this project?

      • hi priyanka… the capacitors can be of any type but it is preferable to use ceramic disc capacitors

      • you can use any antenna. even a 10cm long insulated wire will do. copper is the most preferred choice if u r using a wire antenna.

      • sir will you please tell us how the antenna detects the signal and what will it give as output?

    4. sir i got the output for this circuit ,but it works only when the moble in operation .
      I would like to known basic working of IC CA3130 ,and what its function in this circuit

      • i am Patrick says: on May 2, 2014 at 4:33 pm

        i tried the project with alternative IC CA 741 and its fails what can be the problem yet have failed to get ca 3130 or can any body having suply it to me.

    5. I want pcb layout of this circuit to complete the project.
      If you have pcb layout then send me on:-gauravkpatil.973@rediffmail.com
      Please help me.

    6. For details of the circuit, contact me
      Circuit published in Electronics For You magazine from India.

      • abinaya says: on March 19, 2009 at 6:39 am

        i am doin the circuit with my friend and would like to know the basic functioning of ic ca3130. wish to hear from you. bye…….

      • praveen says: on March 30, 2009 at 2:21 pm

        sir im havin problems wid de circuit..de alarm goes off as soon as de circuit is given power..also i wud like to have de design details of de circuit..please help!!!!

      • sir which kind of antenna should be used to improve the range of the instrument

      • harshal says: on April 9, 2009 at 5:37 pm

        sir,will you please tell me all design equations and working of each part,mainly use of capacitor after the antenna and working of ca3130.
        please send me mail on harshal_chimu@rediffmail.com

      • I’m in the U.S.A. I am an electronics engineering student. I was wondering if there is a way for me to get the PCB details for this circuit

      • Ravi Kiran says: on July 20, 2009 at 7:24 am

        Respected sir,
        I am an Engg. student. I am doing the project on mobile bug. can you please tell me the design of the circuit components especially the ic ca3130; and the antenna specifications?
        If you can provide me with any documentation,please kindly forward to my mail ravikiran2mahesh@gmail.com.

        Thanking you in advance,
        Ravi kiran.

      • sir.
        warm greetings!!!
        i need to increase the range of this ckt…..can you pls give me any instruction or any specific component to do this?….you’v said to use a pre-amplifier…..but how it can be assembled…..??? can you give me a component name.?

    7. sushil pangeni says: on March 15, 2009 at 9:15 am

      Even i tried to make the circuit. The first confusion i have is that of the capacitor. I cant find the same capacitors with 8mm lead spacing and 16mm lead length as mentioned in the circuit. Can you please give the model number for the capacitor.

      Somebody please help. Thank You.

    8. hi friends,
      This project will not work for me. It is very difficult to buy the ic3130. I am trying to finish the work. Please give me any comments.

    9. hello sir,i am doin tis project wit my frnd i got the output for this circuit it works even when the mobile is keep at silent mode…
      I would like to known basic working of IC CA3130 ,and what its function in this circuit. Please let me know about tis very soon.

    10. i have lay out digram of mobile bug,contect me 9893130732

      • HELLO, I am student of B.Tech electronics.I need every information abt MOBILE BUG Like PCB LAYOUT,PROJECT REPORTS etc.& how can I extend its radius to bug mobile.Please give me information.My email is MAHESH_6298 @YAHOO.COM & My mobile no. is 9371494051


    12. what type of power supply i must use???

    13. i done this project.it works,but range is very less,how to increase it?can u please tell me all design equations & detail opration of ca3130 & purpose of capacitor after the antenna.please reply as soon as possible.

    14. hii……plssssss help me.we’re doing this as our mini project.we don’t know wat kind of antenna shold be used to improve the range of this bug.now our circuit will detect mobile signals only to a few cms..pls give a soln to dis problem immediately.we want to submit dis within 2 days.

    15. hi..,im doing mini project on mobile bug..,i want to increase the redius which is now its 1.5m..,i want to extend then wt i ve to do?

    16. sir i am working on this project. i wanna know more details about this.
      i couldn’t get ic ca3130, will simple op-amp work?
      what type of antenna should i use?
      plzzz reply
      if anyone can help……plz help me.

    17. iam also on this project i want its lay out diagram plz can you send me it on my email? i want to precise that iam french speaker and i just try my best to speak and write english. please also tell me all design equations and working of each part,mainly use of capacitor after the antenna and working of ca3130.

    18. hi friends,
      i am doing project. what type of antenna can i use for this circuit. pls send me!

    19. i want to do this project can u give some more information so as to understand it better please

    20. rajnish kumar says: on May 6, 2009 at 7:28 pm


    21. amadi uchenna says: on May 11, 2009 at 6:33 am

      Please My Project is on mobile bug. I wish that you help me with recent update on the project topic. thanks

    22. m nadeem akram says: on May 20, 2009 at 6:04 am

      can u send me detial workig of this circut and student of QAU. i will be very thankful to u.

    23. m nadeem akram says: on May 20, 2009 at 6:05 am

      can u send me detial workig of this circut i am student of QAU. i will be very thankful to u.

    24. Hi, I am doing my semestral project on mobile bug because I found out that it is quite interesting. Can u send me the documentation that are related to the project and updates on this project? Thanks.

    25. i am doin my mini project on mobile detector can you send me the documentation of this project…..?
      and can we increase the range of this mobile detector???

    26. I don’t know about disk capacitor.

      Ceramic capacitor. Is it right?

    27. im doing project on this please send me documentation on this
      i also need cell phone jammer documentation

    28. Are you guys able to do a bit of the work yourself?

      There is a nice schematic posted and it only requires a good hand full of components.

      So get up and do your own work for your own university grade!

    29. hi…
      am doing my miniproject on mobilebug….
      if u hav documentation pls fwd to my mail…
      especially its advantages n applicatns,omer_sohel@yahoo.com

    30. HENRY NDIRIKA says: on June 20, 2009 at 5:02 pm

      please how cAn i know the original TS555CN IC

    31. HENRY NDIRIKA. A.K.A OGIDI says: on June 20, 2009 at 5:06 pm

      ABEG OOO

    32. im doing my project on this please send me documentation on this


    34. plz i need the documentation of mobile bug….im doing my miniproject an mobile bug…plz send it me on abdulmuqeet_19@yahoo.com

    35. KALLED MITCHAEL says: on July 20, 2009 at 2:41 pm


    36. iam doing mini project on cell phone detector.can u able 2 send all documentation regarding this topic

    37. I am going to do a project about cellphone detector.Please send all document and cost about it.


    39. i m doing mini project on mobile detector.pls send me the documentation.my id is krashmirao_89@yahoo.com

    40. i am doing this project could u please forwar me details of the circuit

    41. The documentation is already here you dumbasses! So stop asking for it, your not going to get it!

    42. how to increase the area?what is the frequency range??

    43. hi
      i m doing my btech
      and in our college
      we have to make one mini project
      which can be useful to our college
      this mobile detecter can be useful to me
      but i m not getting enough specification of this one
      so can u plz provide me some stuff
      it will be greatfull to me
      thank u

      • hi…i have just finished this design..it is working properly…if you have any problem consult with me……….

      • Can we increase the range by attaching the RF amplifier instead of antenna???
        Do reply fast..

      • Hi kuldeep im a b.tech(ece) final year student and i want to develop a mobile detector for my minor project.so can you provide me with the details of the mobile detector?Plz contact me at Taran.3087@gmail.com

      • Hye Kuldeep
        I’m BE student..
        I’m also run this project for my final year project..
        My project should being detected when the cellphone are switch OFF and switch ON..
        So I need to share your information about this matter..
        Email me : pau_gbest@yahoo.com.my

        I really need your help

      • balakumar says: on September 1, 2009 at 1:06 pm

        i’m doing project on cellphone detector.i need clear circuit diagram and component required for this circuit.

      • Hi kuldeep,
        Did this ckt really work?What antenna should be used.Can you help me out

      • SIVAMAHARAJAN says: on September 20, 2009 at 7:04 am

        i m doing BE
        and in our college
        we have to make one mini project
        which can be useful to our college
        this mobile detecter can be useful to me
        but i m not getting enough specification of this one
        so can u plz provide me some stuff
        it will be greatfull to me
        thank u

      • pls send me the details and specifications of IC3130 which is used as current to voltage converter in mobile bug project to ramya1490@yahoo.com

      • hey i have just started with this project…i got the 1st half result ie the LED is working but theres some problem with the buzzer circuit…it continuosly sounds even when there is no signal….i think theres some problem with the monostable IC circuit….
        can’t we use a suitable amplifier circuit instead of the IC NE555 circuit?????

        what type of antena is used for this circuit?can u plz specify its name?

        n plz do send me any additional information about this project…???

      • I have just started with this project…i got the 1st half result ie the LED is working but theres some problem with the buzzer circuit…it continuosly sounds even when there is no signal….i think theres some problem with the monostable IC circuit….
        can’t we use a suitable amplifier circuit instead of the IC NE555 circuit?????

        what type of antena is used for this circuit?can u plz specify its name?

        n plz do send me any additional information about this project…???
        plz send me the details to my id…sonujigsy@yahoo.in

      • can u plz send me the circuit image and its connections as well as the type & number of components used my mail id is

      • hello,kuldeep,i m a final year student,i was asked to increase the range of mobile bug detector to 5m range,how is it possible,kindly mail me,regarding my prob,it wil be a great support to me,dear

      • wil it work for any activated mobile or for incoming or outgoing calls

      • D.Mohankumar says: on January 25, 2010 at 4:32 pm

        It will detect incoming,outgoing,SMS,Video
        signals of an activated mobile phone even in
        the silent mode.Phone should not be in the off

      • i want all info amd circuit od this project…
        for major project purpose

    44. Cell phone detector IS VERY GOOD.

    45. Hi,am working on this as my project.I need the block diagram stage by stage and the write up.Pls send to my e-mail noheem_ashafa@yahoo.com

    46. I just built this and would like to point out that it only triggers when there’s activity on the phone, such as when it’s receiving SMS or about to ring. It doesn’t detect the presence of the phone otherwise.

      • SIVAMAHARAJAN says: on September 20, 2009 at 7:07 am

        i m doing my BE
        and in our college
        we have to make one mini project
        which can be useful to our college
        this mobile detecter can be useful to me
        but i m not getting enough specification of this one
        so can u plz provide me some stuff
        it will be greatfull to me
        thank u

      • hello,frnd,i m a final year student,i was asked to increase the range of mobile bug detector to 5m range,how is it possible,kindly mail me,regarding my prob,it wil be a great support to me,dear

    47. workig very good in a small region

    48. am interested with the circuit,please tell me how in can increase the range and how to detect.

    49. hi myself shreya…2nd yesr BE…..
      intrsted in dis project….want 2 kno all about it..!!
      any via for hw can v increase d range?…i will b highly obliged if i get all d specifications ab t d components and increasin d range…….send it 2 m_simple2001@yahoo.com

    50. Hi,am working on this as my project.I need the block diagram stage by stage and the write up.can i implement dis on orcad????
      my email id is tusharsrk@gmail.com

    51. Hi,am working on this as my project.I need the block diagram stage by stage and the write up.my id is tusharsrk@gmail.com

    52. advantages & disadvantages & application of
      Cell phone detector or sniffer

    53. can any one tell me the principle it works on?

    54. pls am workin on this for a project. hw can i increase the the area covered n if possible nos of fones detected. pls send the write ups to my mail. sofelsbaba@yahoo.com. 10x

    55. HELP!!!!

      need detail abtract, explaining working of each component briefly

    56. please do tell me more about this project plsss,….
      i need help before 6th of oct

    57. please
      send all information related to cell phone detector…

      • hai,risha i have done this mobile bug as my mini project its working if u need specification just mail me

      • cristopher says: on October 12, 2009 at 2:21 pm

        rishi please help me out we need to defened this project tomorrow it is not working can you help me out? i think there is a problem in the antenna what antenna should we use?we obeyed all the instructios here an still it only beeps for a while not that long..please help me T_T

    58. can u tell me how to design the capacitor c3
      i.e. the lead length of the capacitor as 18mm and with the spacing of 8mm between the leads… moreover it’s said that c3 conjunction with lead inductance acts as transmission line….
      and how to increase the working region???

    59. i want a full circuit diagram of mobile phone

    60. hii….
      i m working on dis project , but i need more theory about the components of dis project.

      • helloo i m shyam i want to take ur help in this project ?? will u help me plz??

      • hi! i done this project if you have any doubt then call me this is my no +919510079083

      • hii….
        i m working on dis project , but i need more theory about the components of dis project.

      • hy bdy.. its great to know that u hav done with it … congratulatins but im getting problem with this the ckt is nt workin at all… please send me the documentatn of dsk capacitor and the type of antenna u used…. bye

      • i want this project, but is it easy to assemble? i need your reply.. ynx

      • D.MOHANKUMAR says: on November 26, 2009 at 5:37 am

        Yes.It is an interesting and useful project. Careful construction on a common PCB will give good result.

    61. the ciruit realy worked
      amazing thx for it
      so thxxxxxxxxxxxxx

    62. The project is very nice….

      • issahaku mohammed says: on February 9, 2015 at 2:44 pm

        pl mr sharani i saw your comment on the cell phone3 detector i would like you to guide me through it

    63. hi! i made this project sucessfully.
      if have any doubt then call me on this no +919510079083

    64. Those who sucessfully done this project can u send all the documentation to tmac_yu@hotmail.com so that i can know wad is the problem with my circuit…
      I cant make my circuit run at all…

    65. i need all the info for this project especially on the antenna part and c3…
      i dont quite understand about those….
      PLz help me as im using this project as my final year project…

      do email me at tmac_yu@hotmail.com
      thnx ^_^

    66. i complete whole ckt and all other parts are ready but it is not working

      i m doubtful about c3 disk capacitor
      i have used one but either it disk or other type .{rectangular/thin box type in shape}
      pLz help me as im using this project as my third year project

      plz.send me all documents related this project on my id hirenraval90@yahoo.in

    67. Hi every1 ds is very gud ckt im workin on it bt i thought of making some modifications like expand da distance upto 3meters and expand da frequancy 2 include CDMA frequancy band so if any1 can help me i’ll b really glad and thankful
      plz contact me at refsam@yahoo.com

    68. Hi my self ashok. I have finished this project succesfully. I want to expand its merits like this device detects the switch on mobiles within a meeting room or exam hall. If any one has any suggesion plz contact with me.

      • dmohankumar says: on November 14, 2009 at 5:03 pm

        I am happy to know that you have completed my circuit Mobile bug successfully.

      • Hi …
        One of my customer is in need of such kind of devices in hyderabad if can have such devices ready pls call me on 9030086500

    69. subash chandra poudel says: on November 14, 2009 at 4:02 pm

      interesting project I loved building this worked perfectly.

      • D.MOHANKUMAR says: on November 17, 2009 at 3:45 pm

        Go ahead. Try to construct the circuit perfectly as per the description given. Definitely it will give a good result.

    70. what cn i do to increase the range of the circuit of mobile bug

      • D.MOHANKUMAR says: on November 17, 2009 at 3:42 pm

        With this design maximum range of the circuit will be around 1 meter depending on the output power of the mobile phone.Experimentation is necessary to increase the range.

      • did you find what you needed to increase the range. could you share it please?

    71. hey guys,
      i have implemented the circuit,

      but the problem is, that the LED glows and buzzer sounds even though there’s no mobile phone 1.5 meters near it!

      so i think the activation of LED and buzzer is not depending on the activation of mobiles, it’s constantly ON!!!

      how do i rectify it??
      i m waiting for ur reply…

      • D.MOHANKUMAR says: on November 17, 2009 at 1:43 pm

        I already placed the construction details of the circuit and problems during assembling and trouble shooting methods. See the post.

    72. priyanka(maitreyi college) says: on November 19, 2009 at 8:35 am

      those who have done this plz do a favour and send me all info abt this at vand.gupta089@gmail.com

    73. PLZ…..
      send today because monday is last day for my seminar

      • buddy im also working on this project n searching for ppt .if you find it plzzzzzzzzzzzz forward this to me.if i got it then i will definately send it to u.9971778084

    74. helo

      i m working on dis project , i need more details and theory about the components of dis project. plz i really need it cuz coming wk is my last wk on it..i do appreciate if i wil get it..forward to my mail snowboy3k@yahoo.com

    75. i am student of fybcs plz tell me about this project.i want to do hobby project in college plz send me more information about this project or any one

    76. i can’t get the ic ca3130. can you sugest ic equalent to that.

    77. hi friends
      you can contact me on my id for word document & power point presentation on mobile bug

    78. Hi i m working on this project. i had assembled all the parts properly but it is still not working can anyone help me. when i turned it on, it doesn’t detect any signal . i had checked with my multimeter there is no variation in the voltage across pin 2 & 3 of opamp. I had by mistake remove the connection of capicantance c4 and resistance r2 from the ground then opamp gives an output of 1.9v continuously and also detects the Rf signal over a 10cm range only but 555 ic still doesn’t work. so plz help me.

    79. lookin 4 more project like this to do cuz i need to submit all to schl as a Proposal..pls do mail to snowboy3k@yahoo.com if u knw anyone..thanks

    80. My mobile phone detector is not working.please help.It’s very urgent

    81. I would like a copy of the circuit and instructions on creating it and using it.


    82. sir iam working on this cell phone detector project in my college. But it was not works. so please give me the full details about this circuit. please it’s urgent.

      • D.MOHANKUMAR says: on December 10, 2009 at 4:59 pm

        MOBILE BUG
        Purpose of the circuit
        This circuit is intended to detect unauthorized use of mobile phones in examination halls, confidential rooms etc. It also helps to detect unauthorized video and audio recordings. It detects the signal from mobile phones even if it is kept in the silent mode. It also detects SMS.

        Mobile phone uses RF with a wavelength of 30cm at 872 to 2170 MHz. That is the signal is high frequency with huge energy. When the mobile phone is active, it transmits the signal in the form of sine wave which passes through the space. The encoded audio/video signal contains electromagnetic radiation which is picked up by the receiver in the base station. Mobile phone system is referred to as “Cellular Telephone system” because the coverage area is divided into “cells” each of which has a base station. The transmitter power of the modern 2G antenna in the base station is 20-100 watts.
        When a GSM (Global System of Mobile communication) digital phone is transmitting, the signal is time shared with 7 other users. That is at any one second, each of the 8 users on the same frequency is allotted 1/8 of the time and the signal is reconstituted by the receiver to form the speech. Peak power output of a mobile phone corresponds to 2 watts with an average of 250 milli watts of continuous power. Each handset with in a ‘cell’ is allotted a particular frequency for its use. The mobile phone transmits short signals at regular intervals to register its availability to the nearest base station. The network data base stores the information transmitted by the mobile phone. If the mobile phone moves from one cell to another, it will keep the connection with the base station having strongest transmission. Mobile phone always tries to make connection with the available base station. That is why, the back light of the phone turns on intermittently while traveling. This will cause severe battery drain. So in long journeys, battery will flat with in a few hours.

        AM Radio uses frequencies between 180 kHz and 1.6 MHz. FM radio uses 88 to 180 MHz. TV uses 470 to 854 MHz. Waves at higher frequencies but with in the RF region is called Micro waves. Mobile phone uses high frequency RF wave in the micro wave region carrying huge amount of electromagnetic energy. That is why burning sensation develops in the ear if the mobile is used for a long period. Just like a micro wave oven, mobile phone is ‘cooking’ the tissues in the ear. RF radiation from the phone causes oscillation of polar molecules like water in the tissues. This generates heat through friction just like the principle of microwave oven. The strongest radiation from the mobile phone is about 2 watts which can make connection with a base station located 2 to 3 km away.

        How the circuit works?
        Ordinary LC (Coil-Capacitor) circuits are used to detect low frequency radiation in the AM and FM bands. The tuned tank circuit having a coil and a variable capacitor retrieve the signal from the carrier wave. But such LC circuits cannot detect high frequency waves near the microwave region. Hence in the circuit, a capacitor is used to detect RF from mobile phone considering that, a capacitor can store energy even from an outside source and oscillate like LC circuit.
        Use of capacitor
        A capacitor has two electrodes separated by a ‘dielectric’ like paper, mica etc. The non polarized disc capacitor is used to pass AC and not DC. Capacitor can store energy and pass AC signals during discharge. 0.22 capacitor is selected because it is a low value one and has large surface area to accept energy from the mobile radiation. To detect the signal, the sensor part should be like an aerial. So the capacitor is arranged as a mini loop aerial (similar to the dipole antenna used in TV).In short with this arrangement, the capacitor works like an air core coil with ability to oscillate and discharge current.
        How the capacitor senses RF?
        One lead of the capacitor gets DC from the positive rail and the other lead goes to the negative input of IC1. So the capacitor gets energy for storage. This energy is applied to the inputs of IC1 so that the inputs of IC are almost balanced with 1.4 volts. In this state output is zero. But at any time IC can give a high output if a small current is induced to its inputs. There a natural electromagnetic field around the capacitor caused by the 50Hz from electrical wiring. When the mobile phone radiates high energy pulsations, capacitor oscillates and release energy in the inputs of IC. This oscillation is indicated by the flashing of the LED and beeping of Buzzer. In short, capacitor carries energy and is in an electromagnetic field. So a slight change in field caused by the RF from phone will disturb the field and forces the capacitor to release energy.

        ROLE OF IC CA 3130
        This IC is a 15 MHz BiMOS Operational amplifier with MOSFET inputs and Bipolar output. The inputs contain MOSFET transistors to provide very high input impedance and very low input current as low as 10pA. It has high speed of performance and suitable for low input current applications.
        The prototype version has only limited range of 2 meters. But if a preamplifier stage using JFET or MOSFET transistor is used as an interface between the capacitor and IC, range can be increased.

      • SIDDHANT MITTAL says: on January 8, 2010 at 3:28 pm

        Dear sir,
        I m building a project on mobile bug so plz get me available the details for the report

      • sir,i m working on this project,but i was asked to increase the range uptp 5 metres,n i m not able to get it,kindly grace me,in response to my problem

    83. hi am working on this project….i need detailed discription and block diagrm..and also working of each block….i do have some doughts…? will it work only when we make a call or sending an sms…? will it show any indication whn cell is on within the range..? do reply plz….am in need of reply…plz..do reply..

    84. hi….friends…am working on mobile bug project…i need more info about it and also its working in a clear manner…plz do help me…its urgent…mail me throu rubyroobs@yahoo.co.in

    85. vl d normal opamp work…r should v use only ic ca3130…?help me

    86. if the mobile is switched it will detect or not

      • No. It won’t detect switched off mobile phones.
        It will detect the active phones while there is incoming or outgoing signals ….

    87. sorry, if the mobile is switched off it will detect or not

      • D.MOHANKUMAR says: on December 20, 2009 at 1:18 pm

        The detector will sense the RF signal only if the Mobile is switched on.Even in the silent mode it will work.

    88. vl d mobile bug works widout monostable timer n buzzer?if not,wat is its role in dis ckt..reply me plz….

    89. yasir noaman(comsats) says: on December 22, 2009 at 4:41 pm

      this circuit is projected it is very good circuit and also good project for clases.
      by moification it can be used for the cell phone activated switch,

    90. hi..can you please explain the design on the basis of values of the resistor and capacitors chosen for it..also the purpose of using r1 and c4 in the circuit..

    91. hi am working on this project….i need detailed discription and block diagrm..and also working of each block….i do have some doughts…? will it work only when we make a call or sending an sms…? will it show any indication whn cell is on within the range..? i was asked to increase the range uptp 5 metres,n i m not able to get it,kindly grace me,in response to my problem.

    92. sir,i want more detail about dis project
      the antennae connection details??
      troubleshooting tips??
      my id: bibin.paul.c@gmail.com

    93. sir,
      can u send me the detailed documents with PCB layout, design of the circuit.
      Iam working on this project.
      send me to: gafed05@gmail.com

    94. thank you sir this very usefull in my school but how can i increase range of this

    95. we are constructing the mobile phone detector,so please provide PCB layout of the ckt.
      And please tell me where to connect mosfet transister to increase the range of the ckt.

    96. Details of the Project are in the post

    97. i am going to mini project on mobile dector .pls send details and doumentation”how do implement this project? pls needful sir pls……………………

    98. I have selected phone detector as my project.
      send me as much information as available .
      the main problem is coming with
      antenna and c3 capactor.
      I didn’t get the use of this two receiver

    99. C3 is the common 0.22 uf disc capacitor. It is easily available. Antenna can be a small telescopic antenna used in pocket radio.If these are not available in your place,you can procure both the components from junk circuit boards

    100. i want to make a working project on cell phone jammer .can some1 help me…….mail to jaspratapsingh@gmail.com

    101. hello sir,
      i have taken mobile bug as my mini project. i got the components but i am unable to design pcb layout using orcad . if possible please send me the pcb layout . its VERY VERY urgent

    102. thanks sir ur ideas were helpful

    103. hello sir
      i am doing this as mini project. I want to know that whether the lead spacing of 8mm for capacitor can be made through wire or its spacing is from the body of capacitor.

    104. 0.22 disc capacitor is a long lead one. If the leads are short, solder two pieces of trimmed leads of resistor to increase the length. Total lead length must be 18mm from the base of disc and spacing between the leads must be 8 mm to get the required frequency

    105. Sir, I just wanna ask u about the C3 capacitor….u said that the spacing between leads shud be 8 mm…. The problem is 8mm is from the top of capacitor??? or is it the spacing between holes where capacitor is to be mounted is to be of 8 mm ??
      Silly Question….but the Important one !! 😀
      Please mail me the pictorial representation !! Thanx 😀

    106. It is not a silly question. It is important to get desired frequency. As you said 8 mm is the distance between the soldering points and 18 mm is the height of the capacitor leads

    107. pls give me the PCB layout ASAP… THX!

    108. I am making the minor project of “Mobile Bug” Plz send me all the information an layout diagram of mobile bug ,,,
      plz send me all documantation at my email address””guru296403@gmail.com””
      plz plz plz its urgent for me…..
      send me soonn….

    109. please send me the all nokia cell phone circuit diagram and components names

    110. indrani chakraborty says: on February 22, 2010 at 11:57 am

      what is the use of r4,r5,r6,c8,c9 in the circuit of cell phone detector

    111. indrani chakraborty says: on February 22, 2010 at 12:12 pm

      what is the use of r4,r5,r6,c8,c9 in the circuit of cell phone detector. thanks

    112. All these are components around the monostable timer

    113. pls send me links to report on mobile bug

      • D.MOHAN KUMAR says: on February 25, 2010 at 10:47 am

        See the next pages.You will get mail address

      • Sir I am working on this project. I have a problem, the LED turns ON and Buzzer too withour any mobile signal.
        so i reconnected circuit and checked each and every component on the circuit but it still doesnt work. I am bothered about the antenna. What is to be placed in place of antenna. I placed a single stranded wire is that correct??
        plz reply sir as i hve to submit the project tomorrow

    114. i need d details of mobile bug as im doing project on it
      plz help

    115. and how to detect d direction of mobile…

    116. can you provide the complete details about the mobile bug

    117. its really nice project,,,but can i replace any other ic instead of ic3130..it is not availabe in my city

    118. hello, cn u plz giv me d details of d mobile phone detector ckt uses of d components in d circuit???? n also y v use dose particular values of dose components???? is der sum sort of mathaticl calculationz involvd???

      plz rply as soon as psbl

    119. Sir, from our college they told us to do the calculation of the values of resistance, capacitance in the circuit.Can u plz help us???

    120. mohankumar sir,
      i am working on this project,when i mount this ckt on bread board the ic 1 out put at pin 6 wrg is about 168mv when phone off & it increases to 300mv when phone switch on. So i think after pcb mounting it will work but after mounting on pcb it varies 150 to 210mv and ckt not triggred.but i observe that if i removed c3 from ic1 pin3 and touched it with naked hands mens it gets gnd ,buzzer & led will work or ckt triggred. & when i connect it again then it gets off. So i conclude that c3 will not wrking proparly as per your advice i solder it with long leads then also same problem i change 3130 twice then also same problem i have build this ckt twice then also same problem pls give me solution,also some test pts vtgs so that i can find faults
      anyway thanks for such good ckt idea

    121. kaushik piparotar says: on October 7, 2013 at 12:48 pm

      I am working in this project but smoller reng of detected mobile..so help me to long reng of detected and many time no tune on buzzer.
      Plz give infermation about this project.
      Email ID:kaushik.piparotar@gmail.com

    122. i am working on this project but the circuit isnt working… it produces sound without ny signal being transmitted :( help me ASAP

    123. my circuit not work in bread board and pcb plz help me

    124. mobile detector says: on November 9, 2013 at 7:32 am

      hi pls send simple circuit of mobile detector and using parts details also pls send to:ramesh00175@gmail.com

    125. i want to know the parts used in this project, i have a college project work, so it would be great if you give me the process and name of the tools used in this project.
      i will be so thank full to you..

    126. sir i am working on this project. i wanna know more details about this.

    127. helo..can you guys explain about antenna and what item that you guys used it for antenna.

    128. kwame-lah odame-lah says: on February 4, 2014 at 5:58 pm

      Hi am kwame-lah,
      i would want to know if a gps can be attached to this device to pin point exactly where the signal from the hidden phone is coming from.
      If so i would really appreciate it if i could get a block diagram and circuit diagram for the two connections.
      thank u

    129. how can use copper wire instead of telescopic type antenna in hidden active cellphone detector?what should be the diameter of the copper wire to capture the RF signal?please reply soon..
      thanking you..

    130. This circuit worked for me.

    131. Xtian Chukwuemeka says: on March 6, 2014 at 9:34 pm





    132. How can iknow the antenna that detects EM signals from cellphone
      in a certain distance range(in meters).please send me reply.

    133. Please Sir, Send me all of the required components, the solder and the soldering iron and the pcb and then drive to my house and tell me how to build it while you do all the work please, its for a project so I can jam cell phones for the mob, i mean.. school. please sir send me the schematic and your life story and your … okay, sorry but it always cracks me up how people don’t want to do any work themselves and just be thankful that an awesome design like this is made freely available thanks to your hard work. :) So thank you very much for sharing this with us. Excellent circuit. I’ve built several different field strength meter designs over the past few weeks and I’m excited to try this one next. Best regards.

    134. please mail me the design equations

    135. Hi to everyone,I am doing this circuit as my mini project I am facing a problem that the buzzer and led is ON when the battery is connected but without any mobile signal. Can anyone help out pls…
      my email id is cinderjeet@gmail.com


    137. please Mr i need your help
      i have find ca3140 instead of ca3130 is it the same ?
      in the datasheet nothing will differ
      but i builded my project and it doesnt work and i dont know why?
      a need a quick answer plz
      thnk u

      • hi Ravan, Use ca3130 only. Circuit won’t work without it.

      • ca3130 is an op-amp. all op-amps does the same thing but their operating frequency ranges are different. i tried this project and it worked for me. i was facing the same problem when i did it the first tym. check if all connections are correct or not and whether all components that should be grounded are properly grounded.

    138. sir,will you please tell me all design equations and working of each part,mainly use of capacitor after the antenna and working of ca3130.
      please send me mail on eljudgeadex@gmail.com

    139. Hi,

      I am looking for a guy in Hyderabad who can make this for with little modification

      please contact me at my email id kishandewangan@gmail.com

      Many Thanks in Advance!!

    140. how can i get the 12 v battery

    141. Sir,
      I am Third year(T.E) engineering student studying in electronics and telecommunication branch from the university of Mumbai.
      i am working on the cell phone detector circuit. After mounting the circuit on breadboard , the buzzer rings and LED is glowing even when the mobiles are switched off .
      I need a solution to rectify this problem at the earliest as my date of finalizing the project is approaching. Please contact me as soon as possible. My contact details are as follows:
      Contact number:1) +91-9699969951
      Thanking you,

      warm regards,
      (Jigar B. Mehta)

    142. You can also use this circuit with 9v battery and capacitor c5 of 47p is not required to be connected.!

    143. i tried the above circuit .my cicuit is working even when i remove the antenna .but when rps is switched of led stops glowing i cnt find the reason for failure i want to submit my project in one week please give me some suggestios so that i can get my project succeeeded.

    144. Is there any one in Chennai to do this project.i am not from ece so i want some one’s guidance.

    145. i tried this circuit but it didnt work so please send me a suggestion pls .many people posted that they got output so pls help me send me your suggestions @durgharam16@gmail.com

    146. Need this kind of devices in hyderabad pls contact us rays techno solutions by shop.in

    147. this circuit is not working for me.led is not glowing and no buzzer sound.anyone plz guide me to finish this project.

    148. This project is 100% working…. jus remove d 47pF capacitor and u r done…. Awesome project… But trying to increase the range… Can anyone help????

    149. how to increase the range of mobile detector

    150. Sir,
      I am working with this circuit.i found difficult in preparig the pcb layout.you provide the layout, but i can’t open it.please. tell me how to open it…thanks…

    151. Can’t open .pcb file..please hellp…..

    152. I built this circuit on a pcb and it works fine.And it’s range is around 6-7 feet.

    153. I built this circuit on a PCB…it is working…Thanks…

    154. Sir…can you tell me which type of antenna can I use instead any expensive one..? Can I use slant telescopic antenna..??

    155. Best article…all info is vry useful…thnkz alot…!!

    156. sir,i m working on this project,but i
      was asked to increase the range
      uptp 5 metres,n i m not able to get
      it,kindly grace me,in response to my

    157. Can anyone tell me how to connect a whip antenna on the PCB in this project. Please tell me the connections…

    158. its not working and what type of anteena should i use

    159. i have done this project earlier..actually i want to increase the range of my device actually i need range of 10 meter radius….or else range of a class room for 70 students…
      please would u help me…

      its so mandatory guys… ..

      help me!! out guys

    160. Abubakar Suleiman says: on October 5, 2015 at 9:32 pm

      I need latest update of the circuit if available

    161. led and buzzer gets on even if no mobile phone is present
      what to do now????
      reply asap….

    162. I have made this ckt and it is working. but it is only up to 15-20cm.what should I do for increasing the distance.

    163. I tried this with my daughter for a science project but couldn’t get it to work. I tested the transistor, capacitors and resistors with a multimeter and they were good, except that I couldn’t test the pico capacitors since the multimeter isn’t that sensitive. So I replaced the pico capacitors and the CA3130 and NE555 just to be sure, and it still doesn’t work. Any recommendations? I using a CA3130E but as far as I can tell that should still work. Any help or ideas would be appreciated!

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