An Arduino Temperature/Humidity Monitor

I wrote a brief post a while back about my new Smraza Arduino kit. In all the projects that accompanied the kit, I finally came across one that looks useful to me -- a temperature/humidity monitor. Here are views of that breadboarded up and working.

Next up is to get it working with an Arduino Nano, then I'll see about packaging it up into a hard-wired, enclosed unit that I can put to permanent use in the house.

It's too bad that the DHT-11 sensor's range only goes down to 0°C; I'd like to have a unit for outdoor temperature sensing as well.

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Update -- WEDNESDAY, APRIL 18, 2018

I got the monitor to work with an Elegoo Arduino Nano from Amazon.

At first, I could not get the Nano to accept an upload; I'd get an error every time I tried. I fiddled and monkeyed about with the software, not really knowing what I was doing, then out of nowhere it started to work properly. Pure voodoo.

Anyway, now I can get on with designing a power supply and packaging arrangement.

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Power Supply Built -- WEDNESDAY, MARCH 13, 2019

See this post for the regulated power supply that I made from a 9V AC adaptor and an LM317L three-terminal regulator.

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A Finished, Packaged Temperature/Humidity Monitor

Here's a view of the unit installed and working.

The enclosure is an enamelled steel storage bin that I got from the dollar store. The bin is about 5 1/2" square by 4" deep. That's a generous size that makes for relatively easy prototype construction. I added 3mm threaded inserts and screws at either side for lid fastening. The unit is attached to the wall by a couple of 3/4" steel corner braces.

The DHT-11 sensor is attached to the plenum of the house's furnace, so I can observe conditions right at the exterior of the furnace plenum. I thought that might be a little more interesting than monitoring living quarters temperature and humidity. Here's a view of the sensor.

For a sensor mount, I used a small rectangle of aluminum sheet. The DHT-11 is glued to the aluminum with CA adhesive.

Here's a bare-bones schematic of the Arduino/display interface.

And here's a schematic of the DHT-11 wired to a 1/4" stereo phone plug.

Here are two views of the monitor's innards.

Messy, eh? Getting from a nice neat schematic to a functioning piece of gear is quite a journey.

Anyway, following is the code:

/*
   Author: SMRAZA KEEN
   Date:2016/6/29
   IDE V1.6.9
   Email:TechnicSmraza@outlook.com
   Function:
*/
#include <LiquidCrystal.h>
#include <dht11.h>
dht11 DHT;
const int dht11_data = 6;
int temp = 0;
int hum = 0;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
int inPin = 6;
int val = inPin;

void setup()
{
  int inPin = 6;
  lcd.begin(16, 2);
  lcd.print("  Rouge River ");
  lcd.setCursor(0, 1);
  lcd.print("   Workshop   ");
  delay(2000);
  lcd.clear();
  Serial.begin(9600);
}
void loop()
{
  DHT.read(dht11_data);
  temp = DHT.temperature;
  Serial.print("Temperature=");
  Serial.print(temp);
  Serial.println(" degrees Celsius");
  hum = DHT.humidity;
  Serial.print("Humidity=");
  Serial.print(hum);
  Serial.println(" percent");
  lcd.clear();
  lcd.print("Hum=");
  lcd.print(hum);
  lcd.print("%");
  lcd.setCursor(10, 0) ;
  lcd.print(" Rouge");
  lcd.setCursor(0, 1);
  lcd.print("Temp=");
  lcd.print(temp);
  lcd.write(0xDF);
  lcd.print("C");
  lcd.setCursor(10, 1);
  lcd.print(" River");
  delay(500);    
}

Note the following:

• I left in the original author's name, of course, so no one can accuse me of plagiarism. I have made changes, though.
• I've deleted all comments, aside from the opening one with the author's name. I find that most comments in Arduino code aren't all that helpful; mostly they just clutter up the code.
• I changed the start-up herald to read "Rouge River Workshop", and the running logo to read "Rouge River". Those items are easily changed to read whatever one might wish.
• The code outputs the temperature and humidity readings to the serial monitor, as well as to the 1602 liquid crystal display.

So there we are, a halfway useful Arduino project. I'd like to get hold of a DHT-22 sensor; that would enable construction of an outdoor conditions monitor. We'll see.

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Update -- SUNDAY, MARCH 17, 2019

I modified the code to report Fahrenheit temperature as well as Celsius. Here it is:

/*
   Author: SMRAZA KEEN
   Date:2016/6/29
   IDE V1.6.9
   Email:TechnicSmraza@outlook.com
   Function:
*/
#include <LiquidCrystal.h>
#include <dht11.h>
dht11 DHT;
const int dht11_data = 6;
int temp = 0;
int hum = 0;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
int inPin = 6;
int val = inPin;

void setup()
{
  int inPin = 6;
  lcd.begin(16, 2);
  lcd.print("  Rouge River ");
  lcd.setCursor(0, 1);
  lcd.print("   Workshop   ");
  delay(2000);
  lcd.clear();
  Serial.begin(9600);
}
void loop()
{
  DHT.read(dht11_data);
  temp = DHT.temperature;
  Serial.print("Temperature=");
  Serial.print(temp);
  Serial.println(" degrees Celsius");
  hum = DHT.humidity;
  Serial.print("Humidity=");
  Serial.print(hum);
  Serial.println(" percent");
  Serial.print(temp*9/5+32);
  Serial.println(" degrees Fahrenheit");
  lcd.clear();
  lcd.print("H=");
  lcd.print(hum);
  lcd.print("%");
  lcd.setCursor(8, 0) ;
  lcd.print("RRW");
  lcd.setCursor(0, 1);
  lcd.print("T=");
  lcd.print(temp);
  lcd.write(0xDF);
  lcd.print("C");
  lcd.setCursor(8, 1);
  lcd.print(temp*1.8 +32);
  lcd.write(0xDF);
  lcd.print("F");
  delay(500);    
}

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