Summary of what was written earlier:

The effect of the breathing light this time is not very satisfactory. It is not recommended to reproduce this project. When I learn how to light the microcontroller, I will come back to optimize this project.

1. Project introduction

This project is based on the operational amplifier LM358 and peripheral circuits to drive 20 LED lamp beads of different colors.

2.Circuit introduction

The main chip is LM358, which is a dual-channel low-power differential operational amplifier. It has the characteristics of single and double power supply. It has high open-loop gain, internal compensation, high common pattern and good temperature stability, and has the characteristics of output short-circuit protection. It can be used in sensor amplification circuit, DC amplification module, audio amplification circuit and traditional operation amplification circuit.

Chip pin definition:

Physical pin location:

Typical applications:

A triangular wave signal generator is formed by LM358 and peripheral circuit. The tride constitutes a common collector circuit, which amplifies the triangular wave signal added to the base, and because the voltage of the base is a triangular wave clamped on the DC signal, the output voltage of the emitter is an upward triangular wave signal, which can control the brightness of the LED lamp and form the effect of breathing.

The potential of pins 3 and 6 of LM358 is fixed. When the potential of pin 2 is lower than the potential of pin 3, pin 1 outputs high level, that is, T1 is turned on and the LED is on. The potential of pin 2 is provided by pin 7. When the potential of pin 5 is higher than that of pin 6, pin 7 Output high level. The interconnected comparator composed of these two op amps switches T1 on intermittently and lights up the LED.

Draw the schematic diagram according to the reference diagram:

Draw the PCB after the schematic is drawn:

The PCB board frame is drawn in the shape of a Christmas tree.

After drawing, you can insert the prepared picture to see the effect of color silk screen printing.

At the same time, adjust the position of the LED so that the LED is placed where you want it to be bright. At the same time, place the components on the back to make the front beautiful and beautiful. The wiring on the front is drawn in the shape of a big tree.

Echoing the own picture, at the same time clean all the silk screen printing positions on the PCB to make the board surface clean.

PCB 3D Preview

3.Physical Display

PCB physical photos

PCB-front

PCB-Backside

Welded physical pictures

Front

Reverse side

Summary of actual problems encountered:

After the board was completely soldered, I found that some of the LED lights were on and some were not. I didn’t know why. I measured the voltage at both ends of the LED and found that the voltage was only 1.6v-2.0v. I also checked the LEDs of different colors. After looking at the driving voltage, I discovered that the driving voltage is also different for different colors.

It can be seen that the driving voltage of orange and red is relatively low and can be lit directly.

The driving voltages of white, blue, and green are relatively high, ranging from 2.6V to 3.6V. All the problems were found. Due to the difference in voltage, some colors of lights can light up normally, while others cannot.

The temporary solution is to remove the current limiting resistor and instead solder a separate resistor in front of each red LED and orange LED to reduce the voltage.

However, it is very troublesome to solder the resistor and LED on the same pad, but in order to achieve the effect of both lights, this is the only way.

When all the LEDs can light up normally, a new problem is discovered, that is, the breathing effect of the LEDs is not synchronized, which should be caused by different driving voltages, because the LM358 is used to realize the rise and fall of the voltage to realize the LED lights. Breathing effect, but because two types of LEDs with different driving voltages rise and fall at the same time, the LED driven by a low voltage will light up first and then turn off, and the LED driven by a higher voltage will turn off again before it starts to light up. As a result, the breathing effects cannot be synchronized, some are fast and some are slow.

In the end, it is better to use a microcontroller to directly drive the LED light, so that it is not affected by the voltage. It is also best to use a WS2812B type RGB light, so that the driver chip is integrated into the light and it can have three RGB colors.

When I learn to drive the WS2812B RGB lamp beads, I will optimize this project again.

At present, it is not recommended to reproduce this project, which is considered a somewhat failed attempt.