on video Super Effect LED Buzzer Circuit For Bicycle | Horn - electrical and electronics technology degree

Super Effect LED Buzzer Circuit For Bicycle | Horn

In this project, we are going to make a digital bicycle horn with customizable sounds, we can produce up to 4 different sounds, and each track is saved on a micro-SD card in .mp3/wav format, we have 4 button inputs for Playing sounds, each button is assigned to each track in the micro-SD card. Also, it has a rechargeable battery, you can charge the battery with USB C, I also include a battery recharge indicator LED on the back side, and there is a small switch for ON/OFF. It is made from readily available components and completely 3D printable body parts.

Modeling in Autodesk Fusion 360

Used Fusion 360 to plan and design my project. The main body is designed to hold the battery and electronics without needing screws—it just snaps into place. To make sure everything stays secure, I used some hot glue. The button pad is also completely 3D printed including the button caps. I found some accurate models of the modules online. That made the design process much easier, all design files are given below

I 3D printed all of this in PLA+ from Numakers. I used black and orange filament. which is a great combination. 0.2mm layer height and 100% infill, if you don't have a 3d printer you can find online 3d printing services

Before assembling we need to preset the voltage on MT3608, if you buy a new module you need to turn the potentiometer around 20 times or more in a counterclockwise position and then once you get the regulated voltage at the output you can use the module. Connect your battery to VIN+ and VIN- and set the voltage to 5v. Measure it from the OUT+ and OUT- using a multimeter after that remove the battery input

MP3-TF-16P always comes with a header pin pre-soldered but we need to remove it for this project, it is not easy if you don't have the right tools, I used a combination of desoldering pump and plier for removing the header pins. Try not to damage related components from the PCB. This tutorial helps me a lot

I always like to upload the code to the microcontroller before assembly. Here we are using a tiny Xiao SAMD21 from the Seeed studio, It carries the powerful ATSAMD21G18A-MU which is a low-power microcontroller.

After adding Xiao board to IDE we need to install the library for MP3-TF16P, a useful tutorial for installing the library link

Now we can start the assembly.All components are placed in the side wall for utilizing the space and easy wiring

Speaker Unit Assembly

Step 1

Remover the 2 charging status led

Step 2

Connect wires for 2 LED +ve terminals is common, and one -ve for red and -ve on blue

Step 3

Connect the led wires to the BMS

Step 4

Push down the BMS and LED through the 3D print using a nose plier. Don't damage the led

Step 5

We need to wire up the battery to the BMS, connect the +ve terminal of the battery to the B+ of BMS and -Ve to the B-, soldering place the battery on a 3d printed slot

Step 6

Solder two wires to the power switch, push in the power switch to the 3d printed slot

Step 7

Connect the BMS OUT+ to the VIN+ of MT3608 and VIN- to the second terminal of the power switch, you can insert MT3608 into the 3d printed slot

Step 8

Pre-soldered the wires for the xiao with an appropriate length of the wire

Step 9

Strip down 20mm of wire from the 5-core wire

Step 10

Run the wire through the hole in the main body

Step 11

Connect the 5 core wire to GND, D0,D1,D2,D3 pins of the xiao

Step 12

Push down the wire and xiao into the 3d printed slot and glue the 5-core wire and xiao with a hot glue gun

Step 13

Connect the VUSB and GND of Xiao to the +VOUT and -VOUT of MT3068 respectively. After that, we can connect Xiao and MP3-TF-16P. Xiao D6 and D7 to RX and TX pin of MP3-TF-16P, xiao VUSB, and GND to the VCC and GND of MP3-TF-16P. Also, solder two wires from MP3-TF-16P for the speakers.

Step 14

After completing the wiring we can glue the MP3-TF-16P to the 3D-printed slot

Step 15

Connect the speaker

Step 16

Place the speaker inside the main body and align the screw holes

Step 17

Insert the speaker grill into the front cover

Step 18

Screw in the front cover to the main body with M3*12mm

Step 19

Insert a m3 nut into the slot in the mounting point

Step 20

Put the bicycle mount to the main speaker body and tighten it with M3*20mm screws

Step 21

Insert the m3 nut into the mount

We just completed assembly of main speaker unit