Mobile Bug is Scoring

My most attracted circuit is Mobile bug published in Electronics for You few years back. More than 500 students selected the Mobile bug as their project in Electronics Engineering. Some intelligent students have modified the circuit very interestingly and some have constructed the circuit with professional touch. See how Erna Tamizi from Malaysia constructed the Mobile Bug with professional touch and  recorded the Video to show its working.

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Steve Brown says an inspiring comment on my Mobile Bug circuit published in EFY……….. 

Congratulations on developing such a simple detector for mobile phone detection.
It has clearly created a lot of interest since you first published in 2008 and i am sure
you must be getting tired of responding to queries and questions about it.

Just wondered if you had carried out further work to make the design work at a lower
battery voltage e.g 3 – 5V (Li Po etc) and make it more band-limited to reduce pick-up
from DECT and WiFi LAN at around 2.4GHz. The limitation will probably be the CA3130
which is only guaranteed down to 5V but i know it will probably work down to 3 – 4V.
The NE555 can easily be replaced with an LMC555 which will operate down to 1.5V.
The design should also work for the CA3140 op-amp. Is there a low voltage equivalent
that can work equally as well as the 3130/3140?

I have read your extended explanation of how circuit works and was a little bit confused
by the need for the both 5-inch antenna AND the 0.22uF capacitor. I assume the 5-inch
anntenna collects the RF signal (tuned partly by the 22pF caps) and the 0.22uF acts as
a tuned resonator at GHz frequency?

Anyway, thanks once again for publishing your design and allowing people to experiment
with electronics. I am sure you have made one or two enterprising individuals quite wealthy developing this idea into a commercial bug-detector product….. Through e-mail.

5 responses to “Mobile Bug is Scoring

  1. Mohankumar D,

    I’m working on the final design of the faculty of electrical engineering.
    The proposed work would be a detector circuit coupled to a circuit Blocker cellular (3G, GSM / CDMA and DCS).
    Detector and blocking cell


    Detect and block unauthorized use of cell phones in prisons case, evidence rooms, contests, theaters, cinemas, via a control cell.

    The blocker can block the signal, but does not identify the user.
    The detector picks up the signal, but not automatically prevents the connection is complete and in the case to avoid their misuse (This link can lead to crime for example).
    Since the two together, perfectly controlling the misuse of the phone (which detects the signal is being sent, facilitating the identification of the user and automatically blocks the signal)
    Blocker was purchased from a manufacturer of mobile phones on the market, mounted the detector circuit and coupled the same cell through a relay.
    The project works like this, the blocker remains switched off and the detector circuit detects the signal from the phone, the same output to power the piezzo_buzzer (bell), was fed a relay. A contact (NO) would make the seal and another (NA) replaces the button (on / off) of the blocker.
    The project was tested and the circuits work very well, without interference from each other.

    Please find attached photos of the project.

    Figure 8 – Circuit blocker with the phone still on / off switch attached to it.

    Figure 9 – Circuit of the cell without the blocker on / off switch and already connected cable instead.

    Figure 10 – Circuit detector coupled with relay

    Figure 11 – detector circuit coupled to the blocking circuit.

    I’m asking help on some outstanding issues that are missing to complete the job:
    -I need a circuit (DIAGRAM) blocker cellular (3G, GSM and CDS), for myself I could mount it and replace the manufacturer.
    -I also need the PCB in the detector cell size, since the site is blocked and I could not print.
    -I also wanted to increase the range of the detector to 10m (as you would that change?).

    I ask please help to complete the work and permission to use the circuit of the detector at work, as well as all documentation.

    From already thank you for your attention and await response.

    Good morning,
    I’m Marcelo, Brazilian electrical engineering student 10 p, m working on your cell phone detector project. I did the assembly of the circuit and it worked, but the working distance was only 15 cm. kindly tell me how do I increase the distance of work, you could also send me more details about the antenna and capacitor C3. About C3 doubt about the lead terminal spacing of 18mm and 8mm.
    I thank you for your attention and await response. I’m saying that the detector will have to work with 5th 6m in ação.Gostaria please to send me a jammer project, in order to garner the two circuits and conclude our work.
    We, here in Brazil, imprecionados you with your work, your designs are great, since we are already very thankful for providing aid so important to science and development of people who are interested in electronics.