关于NTC温度传感器电路中接的其它电阻和电容的作用 请问图中电阻R3和电容C1有何作用。这是一个用单片机和热敏电...
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C1\u8de8\u63a5\u4e0e\u7535\u6e90+\u4e0e\u5730\u4e4b\u95f4\uff0c\u663e\u7136\u662f\u6ee4\u6ce2\u7684\u4f5c\u7528\u3002
R3\u4e32\u63a5\u5728\u6676\u4f53\u4e09\u6781\u7ba1Q2\u7684\u96c6\u7535\u6781\u4e0a\uff0c\u662f\u4e09\u6781\u7ba1\u7684\u8d1f\u8f7d\u7535\u963b\uff0c\u51b3\u5b9a\u4e86\u4e09\u6781\u7ba1\u5bfc\u901a\u65f6\u7684\u7535\u6d41\u3002
\u7535\u8def\u5de5\u4f5c\u539f\u7406\uff1a
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R2，用于分压，输出Vadc=Vcc*NTC/(NTC+R2)，输出电压
/ NTC温度对应的ADC值查找表
// R25=10k,B=3950,Rup=10k,ADC=12bit
static const uint16_t cNTCTable[] = {
3887, 3874, 3860, 3845, 3830, 3813, 3796, 3778, 3760, 3740, // -29~-20
3720, 3698, 3676, 3653, 3629, 3604, 3578, 3551, 3524, 3495, // -19~-10
3465, 3435, 3403, 3371, 3337, 3303, 3267, 3231, 3194, 3156, // -9~0
3118, 3078, 3038, 2997, 2955, 2913, 2870, 2826, 2782, 2738, // 1~10
2693, 2648, 2602, 2556, 2510, 2464, 2417, 2371, 2324, 2278, // 11~20
2231, 2185, 2139, 2093, 2048, 2002, 1957, 1913, 1868, 1825, // 21~30
1781, 1739, 1697, 1655, 1614, 1574, 1534, 1495, 1456, 1419, // 31~40
1382, 1346, 1310, 1275, 1241, 1208, 1175, 1143, 1112, 1081, // 41~50
1052, 1023, 994, 967, 940, 914, 888, 863, 839, 815, // 51~60
792, 770, 748, 727, 707, 687, 668, 649, 631, 613, // 61~70
596, 579, 563, 547, 532, 517, 502, 488, 475, 462, // 71~80
449, 436, 424, 413, 401, 390, 380, 369, 359, 350, // 81~90
340, 331, 322, 314, 305, 297, 289, 282, 274, 267, // 91~100
260, 253, 247, 240, 234, 228, 222, 217, 211, 206 // 101~110
};
// NCT温度表数目
#define NTC_TABLE_COUNT (sizeof(cNTCTable) / sizeof(cNTCTable[0]))
// NTC温度表起始温度
#define NTC_TABLE_T_FIRST (-29)
/*-----------------------------------*/
// 二分法查NTC温度表
static uint8_t NTC_SearchTable(uint16_t adc_val)
{
uint8_t s_idx, m_idx, e_idx;
uint16_t m_val;
// 检查数据合法性
if (adc_val > cNTCTable[0] || adc_val < cNTCTable[NTC_TABLE_COUNT - 1]) {
return 0xff;
}
s_idx = 0;
e_idx = NTC_TABLE_COUNT - 1;
// 二分法查找
while (s_idx + 1 < e_idx) {
m_idx = (s_idx + e_idx) >> 1;
m_val = cNTCTable[m_idx];
if (adc_val < m_val) {
s_idx = m_idx;
} else if (adc_val > m_val) {
e_idx = m_idx;
} else {
return m_idx;
}
}
return s_idx;
}
// 测量NTC和固定电阻分压
uint16_t NTC_ADCConv(void)
{
uint16_t val;
// Enable ADC1 clock
CLK_PeripheralClockConfig(CLK_Peripheral_ADC1, ENABLE);
ADC_DeInit(ADC1);
// Initialise and configure ADC1
ADC_Init(ADC1, ADC_ConversionMode_Single, ADC_Resolution_12Bit, ADC_Prescaler_1);
// ADC_CLK=2MHz, SamplingTime=8us
ADC_SamplingTimeConfig(ADC1, ADC_Group_SlowChannels, ADC_SamplingTime_16Cycles);
// Enable ADC1
ADC_Cmd(ADC1, ENABLE);
// Enable ADC1 Channel 14
ADC_ChannelCmd(ADC1, ADC_Channel_17, ENABLE);
// Start ADC1 Conversion using Software trigger
ADC_SoftwareStartConv(ADC1);
while (ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
val = ADC_GetConversionValue(ADC1);
ADC_Cmd(ADC1, DISABLE);
CLK_PeripheralClockConfig(CLK_Peripheral_ADC1, DISABLE);
return val;
}
/*-----------------------------------*/
// 初始化
void NTC_Init(void)
{
// PB4, ADC1_IN14
GPIO_Init(GPIOB, GPIO_Pin_1, GPIO_Mode_In_FL_No_IT);
}
// 取得温度
// 参数：返回温度整数部分，返回温度小数部分
// 返回：是否获取温度成功
uint8_t NTC_GetT(uint16_t adc_val)
{
// uint16_t adc_val;
uint8_t idx;
uint8_t tempreature;
const uint16_t *pt;
int8_t *t_z;
uint8_t *t_f;
// adc_val = NTC_ADCConv();
idx = NTC_SearchTable(adc_val);
if (idx == 0xff) {
return FALSE;
}
pt = cNTCTable + idx;
*t_z = idx + NTC_TABLE_T_FIRST;
*t_f = (*pt - adc_val) * 10 / (*pt - *(pt + 1));
tempreature = *t_z+*t_f;
return tempreature;
}
测试出来的温度值一直是20.就指教哪里错了我的电路图和你的电阻NTC是反的
绛旓細R2锛岀敤浜庡垎鍘嬶紝杈撳嚭Vadc=Vcc*NTC/(NTC+R2)锛岃緭鍑虹數鍘
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