#816 DHT11 Unified Sensor Library Test
Using the Adafruit Unified Sensor Library to log temperature and humidity from a DHT11 sensor.
Notes
This is a test of the Adafruit DHT Sensor Library with the unified sensor framework.
See LEAP#301 DHT11 Basics for an introduction to the DHT11 sensor, and LEAP#815 DHT11 Sensor Library Test for an example using the Adafruit DHT Sensor Library without the unified sensor framework.
Circuit Design
I am using a DHT11 that is mounted on an adapter board that includes pull-up resistor for the data line, and a decoupling capacitor, similar to “New Temperature and Relative Humidity Sensor DHT11 Module with Cable for arduino Diy Kit” (aliexpress seller listing).
The schematic below shows the relevant components if a mounting module is not used. Designed with Fritzing: see UnifiedSensorTest.fzz.
Demonstration Script
The DHT11 uses a single-wire two-way communications protocol.
The Tester.ino sketch simply outputs current readings to the console.
Requires the following Arduino libraries:
It is based on the DHTtester.ino example.
#include <Adafruit_Sensor.h>
#include <DHT.h>
#include <DHT_U.h>
const int DHT_PIN = 2;
const int DHT_TYPE = DHT11;
DHT_Unified dht(DHT_PIN, DHT_TYPE);
DHT dht_functions(DHT_PIN, DHT_TYPE); // only needed to access computeHeatIndex
uint32_t delayMS;
void setup() {
Serial.begin(115200);
dht.begin();
Serial.println(F("DHT11 Unified Sensor Example"));
sensor_t sensor;
dht.temperature().getSensor(&sensor);
Serial.println(F("------------------------------------"));
Serial.println(F("Temperature Sensor"));
Serial.print (F("Sensor Type: ")); Serial.println(sensor.name);
Serial.print (F("Driver Ver: ")); Serial.println(sensor.version);
Serial.print (F("Unique ID: ")); Serial.println(sensor.sensor_id);
Serial.print (F("Max Value: ")); Serial.print(sensor.max_value); Serial.println(F("°C"));
Serial.print (F("Min Value: ")); Serial.print(sensor.min_value); Serial.println(F("°C"));
Serial.print (F("Resolution: ")); Serial.print(sensor.resolution); Serial.println(F("°C"));
Serial.println(F("------------------------------------"));
dht.humidity().getSensor(&sensor);
Serial.println(F("Humidity Sensor"));
Serial.print (F("Sensor Type: ")); Serial.println(sensor.name);
Serial.print (F("Driver Ver: ")); Serial.println(sensor.version);
Serial.print (F("Unique ID: ")); Serial.println(sensor.sensor_id);
Serial.print (F("Max Value: ")); Serial.print(sensor.max_value); Serial.println(F("%"));
Serial.print (F("Min Value: ")); Serial.print(sensor.min_value); Serial.println(F("%"));
Serial.print (F("Resolution: ")); Serial.print(sensor.resolution); Serial.println(F("%"));
Serial.println(F("------------------------------------"));
delayMS = sensor.min_delay / 1000;
}
void loop() {
delay(delayMS);
sensors_event_t temperature_event;
sensors_event_t humidity_event;
dht.temperature().getEvent(&temperature_event);
dht.humidity().getEvent(&humidity_event);
if (isnan(temperature_event.temperature)) {
Serial.println(F("Error reading temperature!"));
return;
}
if (isnan(humidity_event.relative_humidity)) {
Serial.println(F("Error reading humidity!"));
return;
}
float heat_index_c = dht_functions.computeHeatIndex(temperature_event.temperature, humidity_event.relative_humidity, false);
Serial.print("Humidity: ");
Serial.print(humidity_event.relative_humidity);
Serial.print("%\t");
Serial.print("Temperature: ");
Serial.print(temperature_event.temperature);
Serial.print("˚C ");
Serial.print("Heat index: ");
Serial.print(heat_index_c);
Serial.println("˚C ");
}