Humidity/Temperature sensor.  Hooked up to Arduino UNO r3. 

For this blog I am going to use this symbol ( * ),  which denotes a time-saver
A time-sever is information on how-to do something.  
I will use the string literal "ALERT" for something you have to do.


This RHT03 is a Humidity and Temperature Sensor is made by Maxdetect.


Parts for the Project

Parts needed for project: (Besides the RHT03. You have it already, right?).
You can purchase it here.  I only found it at Sparkfun.  I could not find it at Adafruit.
And Amazon has it currently but bundled into a bucket purchase from Sparkfun. (That could be a good way to go; get it all right now ! ) 

  1. Arduino UNO r3.   (Be careful not to buy a Chinese clone)
    You can also purchase directly from the Arduino USA website here.
  2. Breadboard.  (There are many boards on the market to choose from.  I recommend a medium to large size board.  Don't get the really small boards; they are difficult to work with wires and components as you add more electronics. )
  3. Wires.  (You can usually buy wires bundled with an Arduino.).
  4.  You need a USB (Universal Serial Bus) 2.0 A-Male to B-Cable.  (I recommend a 4 to 6 foot cable for projects).
    Places to purchase from:  [I don't get any kickbacks: I am just saving you time on searches.]
    a. Sparkfun. ( Located in Niwot,Colorado they have a wide assortment of...well
    almost everything. )
    b. Adafruit.  ( They too have a great source of supplies and tutorials and are
    competitive with Sparkfun.)
    c. Digikey.  (A Speciality Store for the really smart engineers, like us.)
    d. Amazon.  (Who?)

Quick Facts to know about the RHT03:

  • Output is a calibrated digital signal.
  • Has a single-row of four pins for wire connections.
    1. Pin 1 connects to the 3.3 (Vcc) voltage pin on Arduino.
    2. Pin 2 connects to the Data Signal.   ( It connects directly to the digital pin on your Arduino UNO and a 1 K Ohm resistor.  The signal path in general is; Data-signal to digital signal to 1K Ohm to Vcc   I used Pin 7).
    3. The Pin 3 is NULL: not used.
  • Power supply needed is 3.3-6V DC.

The Project.


[ Safety check: You want to ensure you DO NOT have any static electrical charge on your hands.  So, touch your closest friend or family member. "Zap!"  Discharge complete.  I'm just kidding.  Please...really...simply touch a metal surface area. (I am not responsible.) ]

B. Computer and Arduino Setup.

Alright, turn on the PC.  ( I am using a Windows PC/ WIN 10)
Grab your other hardware: one Arduino UNO.   (No silly, not the card game.)
If you haven't already downloaded the IDE for the UNO do so now here.
    (*)     1. Important info to know about libraries.  The Arduino "libraries" 
                  are something you need to know how to use well.  I know the frustration.  It ate
                  up valuable time working on my project.  The simple process is right
                  here.  ( I now wish it so for all.)   You will find "libraries" in IDE: under sketch->
                  libraries. You will find a main "Arduino" folder on your PC computer in
                 the File Explorer.  In the main folder named Arduino there will be a sub-folder
                 named: libraries.  Something like this;

                      C:\Program Files\Programs(x86)\Arduino\libraries 

The reason I am explaining the library is because you will need to download the RHT03 libraries for both this project and the device at Github:

      (*)  Get the project library code at GitHub here
            1.  Click the green-colored "clone or download" button.
                  ******************* ALERT **************************
                  It will start the zip file download automatically. (Do not open the file. Save it!)
             2.  Even after downloading DO NOT OPEN the zip file.  If you mistakenly open the
                  zip file you will not be able to insert it into the Arduino "library" folder.
             3. Open the Arduino's website link "how to install libraries" and follow
                  the instructions to learn how to install a zip file. 
             4.  Once you have installed the zip file into the Arduino IDE, you will be able to
                   select and open it by performing this simple process: 

                    File-> Examples->Examples from Custom Libraries. 

                    The RHT03-Serial.ino file will now be available. The absolute file address
                     on the PC will be something like the following;


Plug in your USB (Universal Serial Bus 2.0 A-Male to B-Cable) cable.  This cable will make a connection line between your PC USB port and the Arduino USB port.

    NOTE: I first open up on my Windows PC my "device manager" window.  Go to->bottom left corner on your PC window->select (left click) the Windows icon-> (where it says," Ask me anything" type in, device manager and then select the "device manager/control panel". Another window pops up. Look down and find the "ports".   You should already see "COM 1" listed under the ports listing. Your now setup and ready.   Now you are ready to see the COM port automatically pop up under the "ports" listing when you plug-in both your Arduino and PC. Bingo!  I like to confirm the connection between the two devices for a double-check. 

    Notice that when you do this it causes both the Arduino and your PC to "recognize" one another ove the serial connection. You will see another "COM<some number here> port suddenly pop up.  That's the port number you also want to see in the Arduino IDE > under "Tools" -> "port".  If you do not see the port; you might need to update the "driver" or troubleshoot the COM port on your PC. Just select the COM that opened up in the Device manager (double-click it) and troubleshoot.

   Now open up your Arduino IDE. (IDE means integrated development environment: basically a nice place to work with your programming and viewing everything in a graphical presentation.)

1. Important info to know about now.  The Arduino "libraries" are something you need to know how to use well.  I know.  It took away valuable time doing an hour of research to find a simple answer. That answer is right here.