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You are here: Home / Transmitter Circuits / Modifying a Bluetooth Headset Device

Modifying a Bluetooth Headset Device

Last Updated on May 26, 2019 by Swagatam 22 Comments

In the previous post we learned regarding the internal circuitry of a typical Bluetooth headset, in this post we'll see how a Bluetooth headset unit can be modified or "hacked" in order to make it work for other personalized applications.

In the previous article we learned how to break open a Bluetooth headset device and also investigated the various components enclosed within.

Identifying the Speaker and MIC

Although most of the stages inside the headset appear to be too sophisticated to digest, the two elements which are still quite traditional are: the speaker and the mic, and those are exactly what we are interested in for implementing the proposed hacking procedures, because these two ports basically become the input and the output terminals of the device.

To be precise it's the speaker outputs that is more useful, which could be assumed to be generating analogue audio frequencies in a push-pull format. This analogue signal can be easily translated and converted into a logical signal for operating a toggling device such as a relay.

In the following couple of images we are able to see the speaker wires which could be simply cut and striped at the ends for accessing the processed analogue frequencies for the required modifications.

Integrating with a Bridge Rectifier Network

Once the above operations are made, it's all about integrating the wires with a bridge network followed by an opto coupler stage, as shown below:

The bridge network converts the differential output response from the Bluetooth speaker outputs into a full wave DC, which is further filtered by the 100uF capacitor to produce a clean DC across the opto input.

The DC is converted into a logical content across the collector/ground of the opto transistor. This output may be configured with any standard flip flop circuit for toggling any desired load.

The above toggling could be initiated by activating the Bluetooth headset with a data from a cell phone or any similar compatible device. Each time the speaker responds, the info gets translated into the above discussed toggling effect over a connected relay.

The Flip Flop Bistable Circuit

A flip flop circuit can be seen in the following figure which could be integrated with the above opto output for obtaining the intended relay operations.

Parts List

R3 = 10K,
R4, R5 = 2M2,
R6, R7 = 39K,
R4, R5 = 0.22, DISC,
C6 = 100µF/25V,
D4, D5 = 1N4148,
T1 = BC 547,
IC = 4093,

The above method explains an easy way of hacking a Bluetooth headset for remotely operating a particular appliance, in the next post (yet to be published) we'll learn how to hack a Bluetooth Headset as a wireless home theater system.




Previous: What’s Inside a Bluetooth Headset
Next: Wireless Home theater Circuit using Bluetooth Headset

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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  1. Search Related Posts for Commenting

  2. Asnar widodo says

    great … mr. swagatam.
    next post I hope you hack bluetooth for communications on a motorcyclist which inserted in each helmet

    Reply
    • Swagatam says

      Thanks Ansar, I’ll try to update it soon. I assume it is for left/right turn signalling and brake lights?

      Reply
  3. Muhammad Rawal says

    Sir can you give me some flow code v5 examples

    Reply
  4. Boakye Emmanuel says

    please sir can i use the Bluetooth hand set to replace the cod-less door bell light control system?

    Reply
    • Swagatam says

      yes you can use it…

      Reply
  5. Percival says

    Excellent guide that gives me ideas. The optocoupler could be replaced by an optical fiber link, for controlled devices that are just out of BT range and/or out of sight. That fourth gate could instead look at pin 4 of N2 and operate a state-indicator LED visible at the BT end. See, I have an older Android tablet I want to use to control several remote locks, and it can handle five BT connections at once.

    Do you know of any hacks that discard the BT functions, and just use the rest of the headset as a standalone rechargeable micropower supply for other projects not-BT-related?

    Reply
    • Swagatam says

      Thanks very much!!
      Sorry, but without the BT function the unit would have no other purpose, could you please explain how do you visualize the unit to serve the mentioned purpose with the BT discarded??

      Reply
    • Percival says

      What I meant was, to utilize just the battery and associated charging circuitry within your average BT headset to power small devices that don't need to communicate over BT.

      I was asked by a friend who bought an expensive Green Lantern power ring "toy" when the (not very good) movie came out to find a way to replace the battery in it with something rechargeable. I noticed that there was room inside the ring for the LiPo battery in a BT headset I had opened up to see what was inside, and room to hide a USB charging port on the outside of the ring. Unfortunately the circuit board was a little too big to also fit, but I couldn't figure out which bits I could cut off without disabling the charging circuitry. I got lucky and found a tiny rechargeable that fit but it still required removal to recharge- I wanted to do it without disassembly and reassembly each time the battery needed charging.

      Since then I've thought of several other ways that could be useful, but the chips in BT sets are hard to find data on- Google is spectacularly unhelpful. I was hoping that you might know of a website that collects that sort of information in one place.

      Reply
    • Swagatam says

      OK understood, in that case you could probably try the second circuit from the following article:

      https://homemade-circuits.com/2013/12/usb-automatic-li-ion-battery-charger.html

      you could try SMD parts for making the unit truly compact.

      Reply
    • Swagatam says

      the above circuit is designed by me….but I have no idea regarding the chips used in a BT module

      Reply
  6. VINCENT MWENDE says

    Hi Swagatam,please help me with a circuit design on how to connect ICL7107 with 2 digit 7 Segment display.Thanks

    Reply
    • Swagatam says

      Thanks Vincent, however I am sorry to say this, I have no idea regarding how a 2-digit display may be configured with the mentioned A/D IC.

      Reply
  7. VINCENT MWENDE says

    Thanks Swagatam am waiting and working for the next,

    Reply
  8. VINCENT MWENDE says

    wow,,,,,,thanks so much swagatam………….just like others am really waiting and working for the next.

    Reply
  9. Arif Aleem Shamsi says

    SIR I AM WAITING FOR YOUR NEXT POST. WHEN WILL IT COME. I AM EAGER TO BUILT IT

    Reply
    • Swagatam says

      Arif, actually it's not difficult, you just have to buy a cheap home theater system and connect the speaker wires of the bluetooth headset with the headphone jack of the home theater….and it will start working like a bluetooth controlled home theater system….any music can be played wirelessly through bluetooth

      Reply
  10. Arif Aleem Shamsi says

    WAITING FOR NEXT POST

    Reply
    • Swagatam says

      thanks for reminding, I'll try to post it soon…

      Reply
  11. Arif Aleem Shamsi says

    Wow ! GREAT AND GREAT PRODUCT

    Reply
    • Swagatam says

      you are most welcome

      Reply
  12. moonlite says

    Sir… great … waiting for next

    Reply
    • Swagatam says

      thanks moonlite ! I'll post it out soon.

      Reply


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