Welcome to IEEE-SEECS

Wireless Bluetooth Speakers

By Behlol Nawaz

During the Fall 2014, the third year electrical engineering students of SEECS (BEE-4) studied their second compulsory electronics course, Electronic Circuit Design (ECD), an advancement of the devices and basic circuits studied in the first electronics course towards circuit design and analysing more complicated and practical circuits.

Due to the nature of the course, students were assigned with a semester project to make them learn something new and create something different. The course instructor, Dr. Hammad  M. Cheema, had set some interesting requirements. Each group of students had to design and construct a useful device, using a Bluetooth Low Energy (BLE, aka Bluetooth 4.0) chip and an Android application. Most of the students used RFduinos for this purpose. RFduino is a very useful microcontroller board with a BLE chip, compatible with coding similar to Arduino’s.

The results were great. Students came up with some very useful, innovative projects solving a number of problems faced by users in daily life. In a series of blog posts, IEEE-SEECS Publications Team will be covering a few projects, their motivation, the basic design and the problems students faced in designing them. Here’s the first in the series, the wireless speakers.

Project name: “BLE controlled Speakers”.

Students: Muneeb Zafar, Abdul Moeed Zafar and Muhammad Alp Arsalan.

            Ever been to a friend’s house and wanted to play your phone’s playlist on his awesome sound system? But you either have to copy songs from your phone’s memory or use the auxiliary port and tie up your phone with the system. Both are kind of a hassle and not very convenient. The creators of this project had faced such a situation and felt the solution they had in mind would fit perfectly with the project requirements.

            What if you had a small device that could be connected to any speakers, connect your phone to it via bluetooth and play songs from the phone, completely wireless?

The Design:

            The overall design of BLE controlled Speakers consisted of an Android music application that communicated with the bluetooth device. The music application had to convert the audio file being played into signals that could be transmitted via bluetooth. Then the device had to process the signal and produce an output for a simple audio jack.

            Unlike other projects, this one did not use an RFduino board. Instead it used a separate bluetooth module’s breakout board (BC217) interfaced with an Arduino Nano. The BC217 did the bluetooth communication and signal processing. The rest was handled by the Arduino Nano. The choice of nano among other Arduino boards was for saving power.

Wireless BluetoothSpeakers.jpg

Illustration 1: Basic Design

Challenges:

            One of the main problems the project members faced initially was that the RFduino board recommended by the instructor was not designed for audio and hadn’t been used for that purpose before. Making it work would be, in the words of one of the students, “a project on its own”. So they were allowed to use a bluetooth chip that had some signal processing functionality on board so that they wouldn’t be starting from scratch. They decided to use “BC127”, a bluetooth 4.0 module with processing for some audio codecs integrated into it.

Wireless-speakers

Illustration 2: BC217 breakout board

Final product:

            The final device demonstrated had a range of 25-30 meters outdoors and about 2 normal sized bedrooms indoors. The music output at the speaker side was crystal clear. One extra feature added was that speech spoken into the phone’s microphone could also be played by the speaker, just like the music. The students who worked on this project said that the first improvement they could make would be reducing the hardware’s size. With the proper tools, the BC217 module itself could be used, rather than the entire breakout board. (In the picture below, the module itself is the small shining part on the red PCB, which as a whole is the breakout board).

WirelessBluetooth Speakers

Illustration 3: The final hardware product

By eliminating the use of the breakout board and using SMDs for the other devices will greatly reduce the overall size of the final product. IEEE-SEECS wishes them good luck in doing so.

Follow the blog for more ECD, DLD and Final-Year Projects coming up soon.

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