Easy Portable Bluetooth Speaker

Watch the video for a better understanding.

Speaker 4-8ohm 30w 4 inch full range link

Bluetooth module link or amazon

BMS link

tda2030a

4 x 18650 batteries

dc-dc isolation converter link

5v regulator (lm7805 or similar)

1/2 inch plywood, accidentally got 3/4 inch.

resistors (100k, 4.7k,150k)

diodes (1n4007)

ceramic capacitors (100nf or 220nf)

electrolytic capacitors (1uf, 4.7uf, 2000uf, 100uf)

perf board

18650 batt case

Switch

Speaker 4-8ohm 30w 4 inch full range link

Bluetooth module link or amazon

BMS link

tda2030a

4 x 18650 batteries

dc-dc isolation converter link

5v regulator (lm7805 or similar)

1/2 inch plywood, accidentally got 3/4 inch.

resistors (100k, 4.7k,150k)

diodes (1n4007)

ceramic capacitors (100nf or 220nf)

electrolytic capacitors (1uf, 4.7uf, 2000uf, 100uf)

perf board

18650 batt case

Switch

Now the first schematic is the amp it self, but to power the Bluetooth module, use the second schematic where the 5v voltage regulator would connect to the Vin and Gnd pins of the converter and +vo and -vo connect to the Bluetooth module.

Before I get into how it works, the potemtiometer in the schematic can be omitted, since we can change volume with our phones.

The three 100k resistors create a voltage divider which offsets the input (music) to half of the supply voltage,this is done so that the music wave can swing fully up and down, which mimics use of a dual supply. The 150k and 4.7k resistors set the amps gain which in this case is 33 since (150/4.7) +1 = almost 33. The 2 diodes clamp the output of the amp to the supply rails, this is used so that output doesn't swing too high or too low. The 1 ohm resistor on the output can be omitted but the 100/220nf cap should hang off the output, the 2000uf cap is used for dc blocking.

I used 4 18650 batteries in series to power the amp which gives me a nominal voltage of around 14.8v, the BMS I bought came with zero instructions, so I didn't trust it enough to charge the batteries, but I looked at the PCB and it does have the charge ic's to charge the batts. There wasn't a connection diagram but I connected it like this and it worked. The only reason I used the BMS is for its short circuit and over discharge protection. I charged them with my lab supply.

B0 --> ground

B1 --> 3.7v

B2 --> 7.8v

B3 --> 11.1v

B4 -- 14.8v

P- and P+ are the outputs and charge inputs

Now the most challenging part, the woodworking job. I used 3/4 inch plywood but I suggest 1/2 inch. I started with a big hole in the center then jigsawed the thing till the speaker fit nice. A big problem I had was the hole I cut was too big for me to create a proper curve with the jigsaw, so I suggest drilling a smaller hole where your jigsaw blade can just fit.

Now to finish it off I used more wood pieces on sides and bottom and just screwed them together, but I used two plastic pieces for a look inside of all my hard work and it wasn't because I was too lazy to cut more pieces of wood.