2in1 (BT+3.5mm[AUX]) Speaker System




Introduction: 2in1 (BT+3.5mm[AUX]) Speaker System

About: An electronics hobbyist

We are very much familiar with Speaker Systems which operate either with Bluetooth or with regular 3.5mm Headphone jack[AUX]. But speaker with both Bluetooth and 3.5mm mode are not readily available in market. But I personally wanted it since my mother always use Bluetooth Speakers for playing her songs and I play games on computer using my 3.5mm cable. So I'm presenting here a Speaker system that is capable of running both with Bluetooth and with 3.5mm cable[AUX mode] and you can also make it by yourself. So let's get started.

Step 1: Parts Required

1. LM380 Audio Amplifier IC (1 or 2 pc) [You can also use any other amp too..I'm personally familiar with this LM380]

2. 1 Bluetooth MP3 player module http://ebay.to/2xEDgi1

3. 1 9V battery with clip

4. 3 Slide DPDT switch

5. Perfboard and solder kits

6. Wires

7. 9-12V power supply

8. 4Ohm speaker (1 or 2 as per your requirement)

9. 1 LED

10. 1 3.5mm Headphone Socket

11. 1 DC barrel jack female port

12. Cardboard or wooden enclosure

13. Tapes( single and double sided),Scissors,

14. 1 7805 IC

15. 470uf(2pc),220uF,100Uf capacitor polar

16. 10K metallic shaft potentiometer

Step 2: Basic Understanding of the Working

The Audio Amp used by me is LM380, popular class AB power amp from National Semiconductor.Now you can use any other IC( obviously circuit must be made likewise as per datasheet). I'm here demonstrating with LM380 since it can produce a maximum of 2.5-3W which is enough for home use.http://www.ti.com/lit/ds/symlink/lm380.pdf Check datasheet here.

Now see the Circuit diagram attached here.You can see in the AUX mode the Right and Left audio channels are merged together (mono) and is fed into the non inverting input(2) of the Amp. Now the ground pin is attached to one side of the DPDT switch.So when the persons ON it then it can produce the amplification. The 10K pot is used to adjust the volume and is attached between the right and left inputs and the 2 pin of LM380. It can be better to use a heatsink to LM380 if you use it with 12-15V.( I used with 9V which is enough and does not require heatsink).Speaker can be of 4W.

Now comes the Bluetooth mode. The Bluetooth MP3 player module can actually connect over phone or laptop with bluetooth and then you can play music.It requires 5V input power. The module has a 3.5mm output pin. You can attach a 3.5mm wire with it and connect it with any amplifier. The Amp will then converted to bluetooth speakers! But I want to use the two modes separately, so I came up with my plan. So take the Right and Left audio out channel of the Bluetooth module and connect to the 10K pot. See the Circuit diagram, it will be more clear. Again here the ground pin is attached to other side of DPDT. So overall it means that at one position of the DPDT, it will be in AUX mode and in the other position it will be in Bluetooth mode. So now I can change it as per my requirement.

Now there is one problem. The Same power supply if shared both with the Bluetooth module and Audio Amp, it creates a typical distortion. So I took a small separate 9V battery and used a 7805 as a 5V regulator to feed the Bluetooth module.Again there is a Switch to ON/OFF the Bluetooth module when required. So there are 3 switches, one is the main supply ON/OFF( Power Switch) , BT Mode/ AUX (3.5mm) mode switching, last one for switch ON/OFF the Bluetooth module.

Check out my link for making the 5V supply for the Bluetooth Module.https://www.instructables.com/id/5V-on-the-Go-Powe...

Step 3: Making the Circuit

Every details regarding everything along with Circuit diagram are given in the previous step. So now grab you Soldering Iron and start soldering every components( If you are new to soldering, first practice with breadboard then go for soldering). After connecting everything check if the circuit is working properly or not. Use the external 9V or 12V supply for the main Amp board. Use a multimeter for continuity and polarity testing. Do not ever by mistake give the BT module 9V, it will kill it, always use the 5V regulator to power it up.

Step 4: Building the Enclosure

Here I've taken a cardboard enclosure for making the box. If you are acquainted with wood works you can build a wooden box too. Now cut the back portion of it to reveal the inside. Now make holes for every components. The potentiometer has a Nut, for attaching it with the front casing, the headphone socket must also have one. Attach the 3 switches, DC power jack, the indicator LED and the finally the Speaker itself. Careful while using hot glue, don't use too much or it might melt the plastic of the sockets.Now make a small hole on the top or side for the air to pass out (while the speaker vibrates). Use double sided tapes to attach the 9V battery and tapes to again close the back part. You can use screws too for attaching switches.

Step 5: Paint It!!!

Now as the enclosure becomes ready use poster or acrylic colors to paint it.I used white, you can use any. Attach a circular small lid on the metallic shaft of the pot for giving a decent look. Mark every thing with a black marker. You can attach a handle too on the top. After all it will give it a decent look.

Step 6: Finally..

Now your speakers are ready. It must work, I've given every details regarding it. Now switch between two modes and play. While using the bluetooth module for the first time with your phone the initial pairing might take a while so be patient. Default pass should be 1234 or 0000. Also check the AUX mode, Take a 3.5mm to 3.5mm cable for testing it with your mobile or laptop.Attach a handle at the top using custom made parts.I used metal pieces and screws for that. Give supply voltage and power on main switch and ROCK ON!!!

Given here two videos so that you can watch in action. For any problem please comment down here or mail me at robosanu1@gmail.com. Thank You!

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    5 years ago

    Nice build!

    I like the point that you made it with the stuff you had, or what you can afford and the skills you have!

    It would definittly wood better to use wood, but if this works, it is okay!

    Well done.


    Reply 5 years ago

    Yes it works just fine..there are two videos describing it at the last step..Absolutely it would be best with wood with air tight gaps..but I did not have the required tools right now with me so I managed with cardboard..