本帖最后由 newsmanager 于 2015-11-21 00:29 编辑

温控风扇系统搭载树莓派，并可从放置在家居的温度传感器里以恒定的间隔读取数据，且当温度过热时激活高压电路的系统。该系统的原理图如下：

***附件停止解析***

该温控风扇包括：
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[*]树莓派1，B +
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[*]5V继电器
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[*]温度传感器DHT11
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[*]分形设计静音系列 R3 80毫米
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[*]12V DC适配器
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温控风扇的相关代码：
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[*]查看温度传感器值：[mw_shl_code=c,true]
#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#define MAXTIMINGS 85
#define DHTPIN 4
int dht11_dat[5] = { 0, 0, 0, 0, 0 };
float read_dht11_dat()
{
uint8_t laststate = HIGH;
uint8_t counter = 0;
uint8_t j = 0, i;
float result = -1;
dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;

/* pull pin down for 18 milliseconds */
pinMode( DHTPIN, OUTPUT );
digitalWrite( DHTPIN, LOW );
delay( 18 );

/* then pull it up for 40 microseconds */
digitalWrite( DHTPIN, HIGH );
delayMicroseconds( 40 );

/* prepare to read the pin */
pinMode( DHTPIN, INPUT );

/* detect change and read data */
for ( i = 0; i < MAXTIMINGS; i++ )
{
counter = 0;
while ( digitalRead( DHTPIN ) == laststate )
{
counter++;
delayMicroseconds( 1 );
if ( counter == 255 )
{
break;
}
}
laststate = digitalRead( DHTPIN );

if ( counter == 255 )
break;

/* ignore first 3 transitions */
if ( (i >= 4) && (i % 2 == 0) )
{
/* shove each bit into the storage bytes */
dht11_dat[j / 8] <<= 1;
if ( counter > 16 )
dht11_dat[j / 8] |= 1;
j++;
}
}

/*
* check that we read 40 bits & verify checksum in the last byte.
*/
if ( (j >= 40) &&
(dht11_dat[4] == ( (dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF) ) )
{
result = (1.0 * dht11_dat[2]) + ((float)dht11_dat[3]/10.0);
}
return result;
}[/mw_shl_code]
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[*]继电器控制(检查温度阈值和启动/关闭继电器)：[mw_shl_code=c,true]
#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#define RELAYPIN 2
#define TEMPMAX 30

int state = 0;
void controlRelay(float avg_t){
pinMode( RELAYPIN, OUTPUT );
if(avg_t > TEMPMAX-state){
digitalWrite( RELAYPIN, HIGH );
state = 1;
}
else{
digitalWrite( RELAYPIN, LOW );
state = 0;
}
}[/mw_shl_code]
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