Wemos D1-DHT11(3.3V!)

2022-05-06
汇总起来几个问题：

1. 串口输出设置波特率时，监视窗口也要同样设置。
2. DHT11是使用3.3V! 这么多年，竟然没有注意这个问题。
3. 下载DHT11的函数库。具体用法不述。一般在函数库中会有详细的例程可参考。
4. 利用Wemos D1的WIFI特性，把DHT11的数据上传到云端。这个待试。参考以下试试：https://blog.csdn.net/yangyan0716/article/details/103071253

#include <dht11.h>
//#define DHT11PIN 8
const int dhtPin=8
dht11 DHT11;
void setup()
{
  Serial.begin(9600);
 
}

void loop()
{
  Serial.println();
  int chk = DHT11.read(dhtPin);
  Serial.print("Humidity (%): ");
  Serial.println((float)DHT11.humidity, 2);
  Serial.print("Temperature (C): ");
  Serial.println((float)DHT11.temperature, 2);
  delay(2000);

}

#include <dht11.h>
dht11 th;   // 注意现在th代表 DHT11 传感器
const int pin = 8;  // 请把 DHT11 的 data pin 连到 arduino Pin 8
void setup( ) {
  Serial.begin(9600);
}
void loop( ) {
  th.read(pin);  // 读取 DHT11 传感器
  Serial.print(String("") + "Humidity = "+ th.humidity + " %");
  Serial.println(String("")+", temperature = "+ th.temperature +".C");
  delay(2500);  // 规定至少要等 2 秒再次读 dht11
}

开始输出是乱码。
据说esp8266默认是115200，改参数后，输出如下。看来不是这个参数的问题。

image.png

感觉是端口错误，改为如下D8：

image.png

此时，输出不乱码了。但是数据错误：难道是器件有问题？按理说新买的，不可能啊。

image.png

急病乱投医。试着将输出强制转换为float.还是不行。

image.png image.png

问题弄明白了：

看到一篇，说DHT11连接3.3v, 重新连接后正常!
https://blog.csdn.net/yangyan0716/article/details/103071253

image.png

---

更详细的参数输出，参考以下例程。这个正常的话，下载到相应的库函数导入，运行是没问题的。但我这边出现错误提示。需要做其他事了。这先放一下。

/* DHT Pro Shield - Simple
 *
 * Example testing sketch for various DHT humidity/temperature sensors
 * Written by ladyada, public domain
 *
 * Depends on Adafruit DHT Arduino library
 * https://github.com/adafruit/DHT-sensor-library
 */

#include "DHT.h"

#define DHTPIN D4     // what pin we're connected to

// Uncomment whatever type you're using!
#define DHTTYPE DHT11   // DHT 11
//#define DHTTYPE DHT22   // DHT 22  (AM2302)
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

// Initialize DHT sensor.
// Note that older versions of this library took an optional third parameter to
// tweak the timings for faster processors.  This parameter is no longer needed
// as the current DHT reading algorithm adjusts itself to work on faster procs.
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println("DHTxx test!");

  dht.begin();
}

void loop() {
  // Wait a few seconds between measurements.
  delay(2000);

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit (isFahrenheit = true)
  float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  // Compute heat index in Fahrenheit (the default)
  float hif = dht.computeHeatIndex(f, h);
  // Compute heat index in Celsius (isFahreheit = false)
  float hic = dht.computeHeatIndex(t, h, false);

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
  Serial.print("Heat index: ");
  Serial.print(hic);
  Serial.print(" *C ");
  Serial.print(hif);
  Serial.println(" *F");
}