# Sixth Lichuang Electric Competition #wuli power amplifier

Note: * is required

Please fill it out during the registration stage↓

* 1. Introduction to project functions

On a rainy day, sit in front of the window and use the amplifier you designed to play your favorite music. The romance of engineering students is so simple!

Features

• The input part adopts AUX plus expansion port; aux is the most commonly used interface in audio projects. It is recommended to use shielded audio cables to prevent interference. The expansion port consists of a 2X3 pin header, providing R&L audio signal input, 3.3V800MA and 5V 4A high current output power supply. An external function board can be designed according to the order of the pin rows, such as connecting a Bluetooth module to realize Bluetooth playback or connecting an FM module to listen to radio; a Bluetooth small board has been designed so far.
• Traditional faders are used to control the volume. You can know the set volume at a glance, so you don’t have to worry about lightning strikes at startup due to random adjustments.
• When the power supply is sufficient, it can drive 2X50W speakers, allowing you to achieve a seamless music experience of playing songs on the first floor and enjoying them on the entire floor. ( Only if you own one building, avoid being hammered! )
• There are heat sinks and silent cooling fans installed inside to ensure that in the 40-degree summer, you can still sit in front of the window, play your favorite music, and enjoy the comfort brought by the sunshine in the dog days.
• The 50cm light strip moves with you along with the music, so you won’t be bored while dancing alone.

*2. Project attributes

The word is exactly what it sounds like, this is a power amplifier that belongs to engineers. The ship-shaped version will only be launched on the Lichuang open source platform. Commercial use is prohibited. If you have any other questions, please comment or contact us via private message. The author has no temper and generally does not bite.

If there is any infringement in other cases, please contact us.

* 3. Open source agreement

Follow the GPL 3.0 open source license

Please fill in during the competition stage↓

*4. Hardware part

The hardware mainly consists of 5 parts: amplifier motherboard , WS2812B light strip , front and rear panels and smart card .

The power amplifier mainboard is mainly composed of a pre-amplifier chip , a post-amplifier chip , a power supply chip and an input part .

The preamplifier chip is NE5532; NE5532 is a high-performance low-noise dual operational amplifier. It is similar to many standard operational amplifiers, but it has better noise performance, excellent output drive capability, fairly high small signal bandwidth, and a wide power supply voltage range. This design uses two pieces of NE5532, which are used for the R and L channels respectively, as shown in the figure:

The post-amplifier part uses the TPA3116 chip, which is also owned by TI. It can load 50W stereo or 100W mono, 4.5V to 26V power supply voltage, analog input and other functions. It is a Class D audio amplifier. This chip is also used in many consumer power amplifier products. It is more common in the market. The peripheral circuit is designed strictly in accordance with the official website data manual. What needs to be paid attention to is the output part. Because the output capability of up to 50W is taken into account, a 10uh 5.4A power inductor is used to reduce heat generation while stabilizing the output. TPA3116 will also generate serious heat when working at high power, so the early design needs to leave space to install a heat sink. The specific circuit is shown in the figure:

The power supply part is composed of CJ7812, AMS1084CM-5.0 and AMS1117-3.3, which provides a total of 3 sets of voltages 12V 1.5A / 5V 4.5A / 3.3V 0.8A for the entire circuit, which can provide sufficient power for later connection of various expansion panels, including large Current WS2812B light strip. The schematic diagram is shown in the figure:

The input part mainly uses the AUX interface, which is input by a 3.5mm audio cable. It also has a 2x3p expansion interface, which can be connected to a Bluetooth board, FM radio board, etc. to provide more functions for the power amplifier; as shown in the figure:

The WS2812B lamp strip is designed using multiple WS2812B lamp beads in cascade, and is controlled by ESP12F as the MCU. The DO of the previous lamp is connected to the DI of the next lamp. It is very easy to use and the circuit is also very simple. In Liugong Dalao's simple Below, 60 lamp beads are used, and the PCB board is 50CM long, bringing a very cool visual experience. It should be noted that the WS2812 lamp requires a relatively large current when operating at 100% brightness. The power supply line needs to be designed as wide as possible and an aluminum substrate should be used as much as possible to prevent the lamp beads from overheating.

Both the front and rear panels are designed with PCB, which is mainly cool (JianDan) and the cost is also very low. The front panel is mainly equipped with faders to adjust the volume, LEDs to display the working status, and switches to control circuit switches. It is connected to the power amplifier board through a cable. Below is a picture of the finished product. I personally feel it is pretty good hahaha O(∩_∩)O

The smart card is a golden finger module composed of ESP12F chips. It is inspired by the old TV set-top box. When I was a child (revealing my age o(╥﹏╥)o), the TV set-top box at home needed to be upgraded every year, and then the parents would remove the smart card from the set-top box. Come out and go to a special place to spend money to upgrade. This is also a good way to prevent peeking at TV (escape~). A similar design is adopted this time, so that ESP12F can be connected to the power amplifier through the slot to drive the WS2812 light strip. When the program needs to be updated, you only need to unplug the smart card and insert it into a specially designed burner. Updated, saving a lot of space on the amplifier board. Below are photos of the smart card and burner:

 Attached: The designed Bluetooth expansion card is used to provide Bluetooth input function to the power amplifier. The actual picture is as shown in the figure:

In addition: How can an exposed circuit board be used as a mature product? Engineering people also have aesthetics (shivering...), so I also designed a casing for this product (the modeling technology is really poor, As long as it can be used, it’s good if it can be used (^o^)/~).

Designed using Fusion360

You need to calculate the dimensions when designing the casing. It would be embarrassing if you find out after 3D printing that it cannot be installed...

Problems encountered

With Liu Gong's blessing, the board basically has no problems, works normally, and the required effects are achieved. But what needs to be paid attention to is the power of the speaker. When outputting high power, you must use thicker wires, otherwise the wires will be seriously heated,,,,, and then there will be no sound. . . .

Attachment: In order to enjoy the coolness brought by music in the hot summer, I installed a 12V cooling fan in the final version to enhance heat dissipation.

*5. Software part

The power amplifier board itself does not involve software programming. It can achieve the required functions if there are no problems with the circuit. This design uses a WS2812 light strip to achieve the spectrum effect, so it requires an ESP12F chip and is programmed using Arduino IDE. The program is Uploading as an attachment has several different effects. The program also uses open source projects and is not commercially available. Users must follow the open source agreement.

*6. BOM list

The BOM table will be automatically generated under the schematic diagram, so I won’t go into details here. Chip prices have risen seriously. If you develop a good habit of summarizing components, you can buy fewer components when designing. As witty as me (✪ω✪)

*7. Contest LOGO verification

Semi-finished board, logo screen printing:

* 8. Demonstrate your project and record it as a video for uploading

Actual before and after photos:

Supplement: The audio output interface and power input interface at the rear end both use DC005 round plugs. However, in order to avoid incorrect insertion, the audio output interface uses a 2.5mm wheelbase, while the power input interface uses a 2.1mm wheelbase, so the power input terminal cannot be inserted. to the audio output port to avoid damage to the power amplifier caused by incorrect insertion to a certain extent.

See the demo video at the bottom of the page: ↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓

Recorded with an old mobile phone, the radio effect seems to be very poor, please make up your mind hhh

Videos will be uploaded to bilibili simultaneously. New up owners will have better videos for everyone in the future. Please like and follow: https://www.bilibili.com/video/BV1vP4y1x7RE/