PWM实现LED渐变效果及彩灯控制

一、硬件

1. 核心电路设计

连接示例（STM32）：

STM32引脚 → RGB LED
---------------------
TIM3_CH2 → R (PB5)
TIM3_CH3 → G (PB0)
TIM3_CH4 → B (PB1)
GND       → 公共地
3.3V      → 电源输入

2. 电气参数计算

• 限流电阻计算：

  

（示例：V_CC=3.3V，V_f=2V，I=20mA → R=65Ω）

• PWM频率选择：

  

（推荐值：500Hz-2kHz）

二、软件

1. 基础渐变算法

// 定义颜色通道结构体
typedef struct {
   
    uint16_t duty;    // 占空比(0-65535)
    GPIO_TypeDef* port;
    uint16_t pin;
} LED_Channel;

// 线性渐变函数
void linear_fade(LED_Channel* channels, uint8_t num_channels, 
                 uint32_t target_duty, uint32_t step, 
                 uint32_t delay_ms) {
   
    static int16_t direction = 1;
    static uint32_t current_duty = 0;

    for(int i=0; i<num_channels; i++) {
   
        current_duty += step * direction;
        if(current_duty >= 65535 || current_duty <= 0) {
   
            direction *= -1;
            current_duty = constrain(current_duty, 0, 65535);
        }
        ledc_set_duty(LEDC_HIGH_SPEED_MODE, channels[i].channel, current_duty);
        ledc_update_duty(LEDC_HIGH_SPEED_MODE, channels[i].channel);
    }
    vTaskDelay(delay_ms / portTICK_PERIOD_MS);
}

2. 呼吸灯实现（STM32 HAL库）

// 定时器配置（TIM3）
void MX_TIM3_Init(void) {
   
    TIM_HandleTypeDef htim3;

    htim3.Instance = TIM3;
    htim3.Init.Prescaler = 72-1;    // 1MHz
    htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
    htim3.Init.Period = 65535;      // 最大占空比
    htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    HAL_TIM_PWM_Init(&htim3);

    // 通道配置
    TIM_OC_InitTypeDef sConfigOC = {
   0};
    sConfigOC.OCMode = TIM_OCMODE_PWM1;
    sConfigOC.Pulse = 0;
    sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;

    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_2); // R
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_3); // G
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_4); // B

    HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_2);
    HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_3);
    HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_4);
}

// 呼吸灯主循环
void breathing_led() {
   
    uint16_t duty = 0;
    uint8_t dir = 1;

    while(1) {
   
        __HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_2, duty);
        __HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_3, 65535-duty);
        __HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_4, 0);

        duty += dir;
        if(duty == 0 || duty == 65535) dir = -dir;
        HAL_Delay(1);
    }
}

三、进阶功能实现

1. 彩虹渐变算法

// HSV转RGB算法
void hsv2rgb(float h, float s, float v, uint16_t* r, uint16_t* g, uint16_t* b) {
   
    float c = v * s;
    float x = c * (1 - fabs(fmod(h/60.0, 2) - 1));
    float m = v - c;

    if(h >= 0 && h < 60) {
    *r = c; *g = x; *b = 0; }
    else if(h >= 60 && h < 120) {
    *r = x; *g = c; *b = 0; }
    else if(h >= 120 && h < 180) {
    *r = 0; *g = c; *b = x; }
    else if(h >= 180 && h < 240) {
    *r = 0; *g = x; *b = c; }
    else if(h >= 240 && h < 300) {
    *r = x; *g = 0; *b = c; }
    else {
    *r = c; *g = 0; *b = x; }

    *r = (uint16_t)((*r + m) * 65535 / 255);
    *g = (uint16_t)((*g + m) * 65535 / 255);
    *b = (uint16_t)((*b + m) * 65535 / 255);
}

// 彩虹渐变主循环
void rainbow_fade() {
   
    float hue = 0.0;
    while(1) {
   
        hsv2rgb(hue, 1.0, 1.0, &r_duty, &g_duty, &b_duty);
        ledc_set_duty(LEDC_HIGH_SPEED_MODE, RED_CHANNEL, r_duty);
        ledc_set_duty(LEDC_HIGH_SPEED_MODE, GREEN_CHANNEL, g_duty);
        ledc_set_duty(LEDC_HIGH_SPEED_MODE, BLUE_CHANNEL, b_duty);
        ledc_update_duty(LEDC_HIGH_SPEED_MODE, RED_CHANNEL);
        ledc_update_duty(LEDC_HIGH_SPEED_MODE, GREEN_CHANNEL);
        ledc_update_duty(LEDC_HIGH_SPEED_MODE, BLUE_CHANNEL);

        hue += 0.5;
        if(hue >= 360) hue = 0;
        HAL_Delay(10);
    }
}

2. 呼吸灯优化方案

// 正弦波呼吸算法
void sine_wave_breathing() {
   
    float phase = 0.0;
    while(1) {
   
        float duty = (sin(phase * M_PI / 180) + 1) * 32767; // 16位范围
        __HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_2, (uint32_t)duty);
        __HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_3, 65535 - (uint32_t)duty);
        phase += 1;
        if(phase >= 360) phase = 0;
        HAL_Delay(1);
    }
}

四、工程实现要点

1. 硬件保护电路

LED驱动电路设计
----------------
MCU PWM → 电阻 → 二极管 → 电感 → LED
                  ↑
                续流二极管

2. 中断服务程序

// 定时器中断处理
void TIM3_IRQHandler() {
   
    if(TIM_GetITStatus(TIM3, TIM_IT_UPDATE) != RESET) {
   
        TIM_ClearITPendingBit(TIM3, TIM_IT_UPDATE);

        // 动态调整占空比
        static uint16_t duty = 0;
        duty = (duty + 1024) % 65536;
        TIM_SetCompare2(TIM3, duty);
    }
}

3. 低功耗优化

// 进入睡眠模式
void enter_sleep_mode() {
   
    HAL_PWR_DisablePVD();
    HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_SLEEPENTRY_WFI);
}

// 唤醒配置
void EXTI0_IRQHandler() {
   
    if(EXTI_GetITStatus(EXTI_Line0) != RESET) {
   
        EXTI_ClearITPendingBit(EXTI_Line0);
        HAL_PWR_DisableSleepDeep();
    }
}

参考代码 基于PWM的LED渐变效果及彩灯 www.youwenfan.com/contentalf/72808.html

五、扩展应用场景

1. 智能照明系统

// 光照感应控制
void ambient_light_control() {
   
    float lux = read_lux_sensor();
    float target_duty = 65535 * (lux / 10000.0); // 0-10000lux
    ledc_set_duty(LEDC_HIGH_SPEED_MODE, RED_CHANNEL, target_duty);
}

2. 节日灯光秀

// 预设灯光模式
typedef enum {
   
    MODE_STATIC,
    MODE_FADE,
    MODE_BREATHE,
    MODE_RAINBOW
} LightMode;

void execute_light_show() {
   
    static LightMode current_mode = MODE_STATIC;

    switch(current_mode) {
   
        case MODE_STATIC:
            set_static_color(0xFFFF, 0x0000, 0x0000); // 纯红色
            break;
        case MODE_FADE:
            linear_fade(channels, 3, 65535, 1024, 50);
            break;
        case MODE_BREATHE:
            sine_wave_breathing();
            break;
        case MODE_RAINBOW:
            rainbow_fade();
            break;
    }
}