Visualise the Sound: Smart Bluetooth Speakers With Spectrum Analyser




About: Engineer maker and inventor

In this instructable, I would like to explain how to build a powerful smart Bluetooth speaker in a very simple way. The radios made a revolution in the 20th century every NEWS including war alerts were sent through the radio communication only. But the due to the use vacuum tubes during those days, size of radios were very big and most of them are packaged in a huge cuboidal box with 2 speakers. In this instructable, I've tried to give the retro look to my smart speaker. It has following features,

1. OLED display to show Date, Time, Day, Humidity & Temperature

2. Spectrum analyser to visualise the Music frequency Spectrum

3. Powerful sound output with around 10 hours of battery life

4. AUX input

5. TP4056 controlled charging unit

6. Bluetooth connectivity using F6188 Module

7. Hands-free mode to receive calls via Bluetooth

Features are cool, so let's make one...

and please don't forget to vote me in contests.

Step 1: Getting Started

Here are the materials required to build this.

1. Foam sheets

2. 18650 batteries 2

3. Arduino Pro mini

4. OLED display 0.96" I2C

5. PAM 8403 audio amplifier module

6. TP4056 charging circuit

7. F6188 Bluetooth module

8. DHT 11 Sensor (optional)

9. RTC DS3231 Module

10. 2 Speakers (From local electronics store or you can scavenge it from old radio) 2W-3W

11. Wood laminate material sheet

Tools required

1. Soldering Iron

2. Hot glue gun or any strong glue

3. Cutter knife

If you have access to laser cutter then it will be easy to cut everything neatly, especially the wood laminate sheets, because it is very difficult to cut it with the cutter knife as it is brittle.

Step 2: Cutting the Layout

The layout design is easy and you can design the way you want, I have attached my design plan which you can directly print it and paste it on material like foam sheet, cardboard sheet or plywood sheet etc. and directly you can cut it. The design attached has a dimension of 12cmx4cmx4cm. The speaker hole is dependent on your speaker dimensions. My speakers were 3cm in diameter so I made a hole using cutter knife and placed my speaker.

You might have to cut the small portion for charging, AUX input and Switch connections on one of the side faces.

Step 3: Let's Connect Everything

The Bluetooth module is the F6188 module which is good and works very well.

You might need to add a heatsink on top of the module as it heats up sometimes.

The speakers are connected to PAM 8403 module and input to the module is given by the both AUX and Bluetooth module.

You can use female AUX connector with the switching mechanism to toggle between Bluetooth and AUX input.

The battery is connected charging circuit and switch which is inturn connected to PAM 8403 and RAW pin of Arduino Pro Mini.

You can use 2 18650 batteries in parallel to increase the capacity of your speaker

.The OLED display talks to the Arduino pro mini via I2C so the Arduino pins A4 and A5 are connected to SDA and SCL pins respectively

Since we're using the RTC module to display the time and the date we need to connect the RTC module DS3231 to the Arduino in an above-mentioned manner as DS3231 is also an I2C device.

The DHT11 Temperature and Humidity sensor is optional and can be conneted to pin no. 2 of arduino pro mini

Connect the A0 pin of arduino to one of the signals such as audio right or audiio left to see the spectrum of audio.

Step 4: Fixing

Using hot glue gun or petroleum glue fix everything after you finish connecting the circuitary.

You can cut wood laminate plates in the same shapes and stick it over your speakers. This gives the retro or the 20th-century radio look.

Step 5: Working

For the spectrum analyzer, I'm using fix fft library with the help of which I can draw lines on OLED display depending on the frequency variation.

Humidity and temperature data is acquired by DHT 11 Sensor.

Date and Time are acquired by the RTC DS3231 module.

When AUX input is plugged in, the Bluetooth gets switch off automatically by ring switch of the 3.5mm female jack.

This Bluetooth module is detected as BK8000L then you can connect it to play the audio seamlessly. It even has a hands-free mode where you can pick up calls.

The pinout and schematics of Bluetooth module are in the data sheet.

Connect the A1 pin to switch which connects the battery. This ensures that display will be always on in normal mode to display date and time and weather info.

When the switch is turned on it will get into the Speaker mode to display the spectrum visualizations.

Step 6: Let's Test

Finally, we're ready to test our speaker. This speaker will work as a clock, a weather monitor and portable and powerful speakers.

I have attached a GIF animation of all steps for quick reference.

Future enhancements

1. Adding FM radio

2. Adding SD card support and mp3 playing capability

3. Adding a booster circuit to use it as a power bank

Please vote me in contests, thanks a lot for your support.



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    12 Discussions


    1 year ago

    Awesome idea! You might consider mounting it all in a cigar box. You can get them pretty cheap at a smoke shop or online, lots of shapes and sizes, and since they're already put together you would only have to cut your holes.

    1 reply

    Reply 1 year ago

    Oh. Thanks a lot for your suggestion.


    1 year ago

    Hey man not trying to sound mean but its a killer project idea however use all wood instead. Looks sloppy as is but with wood would be pretty good. Your smart with the electronics i know you can build a box for that thing. Good job overall.

    3 replies

    Reply 1 year ago

    Thanks a lot for your suggestion on material. The problem I have is I don't have access to the CNC machines or laser cutter and I had to do everything by hand. While cutting wooden laminates I drilled holes using a hand-drill in circular shape, then poked it out. It took almost half an hour per each hole. If I had access I would have directly used CNC machine or laser cutter to cut out the parts. Also wood will enhance the audio quality by its accoustic properties.


    Reply 1 year ago

    You dont need that fancy stuff. But investing in a drill would be a good buy lol. Harbour freight has cheap tools like the rotory tool would work really well for you and its only about 15 bucks us. Keep me posted on your next build you have the mind of a inventor.


    Reply 1 year ago

    Oh. Thanks a lot. I'll upgrade my tools and definitely make next version look good.


    1 year ago

    Actually use 1x4s its roughly the same thickness as the foam but stronger and you can stain it and clear coat it and even assemble it with hot glue. Costs maybe 3 bucks.

    1 reply

    Reply 1 year ago

    Oh, Thanks a lot for the suggestion. Will use that in next version. Currently, I have limitations in accessibility of materials, So I'll upgrade thisin next version.

    SerS 19

    1 year ago

    VEry good, i really like this idea of using arduino in speaker projects, howeer, i lack some power on those speakers

    1 reply