The DHT11 temperature-humidity sensors pt 2

Here’s the graphs from my recent experiment, and here’s the data.

Temperature from 11 DHT11 sensors over 22900 data readings for each sensor

Temperature from 11 DHT11 sensors over 22900 data readings for each sensor

Humidity from 11 DHT11 sensors over 22900 data readings for each sensor

Humidity from 11 DHT11 sensors over 22900 data readings for each sensor

min, avg, max and variance of temperature from 11 DHT11 sensors over 22900 data readings for each sensor

min, avg, max and variance of temperature from 11 DHT11 sensors over 22900 data readings for each sensor

min, avg, max and variance of humidity from 11 DHT11 sensors over 22900 data readings for each sensor

min, avg, max and variance of humidity from 11 DHT11 sensors over 22900 data readings for each sensor

and a brief video…

The DHT11 temperature-humidity sensors

So I have loads of these from an old project that you guessed it – I never got round to, but how accurate are these cheapest of cheap things?

Set up an Arduino/RasPi with all the sensors and get it to read them all back – if all in one location then they should all be the same right? Lets see how accurate they are! I’ll run the test for a week (probably longer) with various conditions and then report back.

oh and some code….


// origional code from ladyada, public domain
#include "DHT.h"
#include
#include

DHT dht0(2, DHT11);
DHT dht1(3, DHT11);
DHT dht2(5, DHT11);
DHT dht3(6, DHT11);
DHT dht4(7, DHT11);
DHT dht5(8, DHT11);
DHT dht6(9, DHT11);
DHT dht7(A0, DHT11);
DHT dht8(A1, DHT11);
DHT dht9(A2, DHT11);
//older sensors
DHT dht10(A4, DHT11);
DHT dht11(A5, DHT11);

float temps[12];
float hmids[12];

void setup() {
Serial.begin(9600);
Serial.println("DHT test!");
dht0.begin();
dht1.begin();
dht2.begin();
dht3.begin();
dht4.begin();
dht5.begin();
dht6.begin();
dht7.begin();
dht8.begin();
dht9.begin();
dht10.begin();
dht11.begin();
SD.begin(4);
}

void loop() {
// Wait a few seconds between measurements.
delay(30000);

hmids[0] = dht0.readHumidity();
temps[0]= dht0.readTemperature();

hmids[1] = dht1.readHumidity();
temps[1]= dht1.readTemperature();

hmids[2] = dht2.readHumidity();
temps[2]= dht2.readTemperature();

hmids[3] = dht3.readHumidity();
temps[3]= dht3.readTemperature();

hmids[4] = dht4.readHumidity();
temps[4]= dht4.readTemperature();

hmids[5] = dht5.readHumidity();
temps[5]= dht5.readTemperature();

hmids[6] = dht6.readHumidity();
temps[6]= dht6.readTemperature();

hmids[7] = dht7.readHumidity();
temps[7]= dht7.readTemperature();

hmids[8] = dht8.readHumidity();
temps[8]= dht8.readTemperature();

hmids[9] = dht9.readHumidity();
temps[9]= dht9.readTemperature();

hmids[10] = dht10.readHumidity();
temps[10]= dht10.readTemperature();

hmids[11] = dht11.readHumidity();
temps[11]= dht11.readTemperature();

Serial.print("Temps ");
for (int i=0;i<12;i++)
{
Serial.print(temps[i]);
Serial.print(", ");
}
Serial.println();

Serial.print("humids ");
for (int i=0;i<12;i++)
{
Serial.print(hmids[i]);
Serial.print(", ");
}
Serial.println();

//write data to SD card
File dataFile = SD.open("dhtdata.txt", FILE_WRITE);
if (dataFile) {
dataFile.print("Temps, ");
for(int i=0;i<11;i++)
{
dataFile.print(temps[i]);
dataFile.print(", ");
}

dataFile.print("Humids, ");
for(int i=0;i<11;i++)
{
dataFile.print(hmids[i]);
dataFile.print(", ");
}
dataFile.println(';');

dataFile.close();
}

//Serial.println(t);
}