A Hand Held Thermo-hygro Meter Based on Arduino With MATLAB Live Data Plotting Feature

Hi friends, in this instructable I would like to introduce you to a good instructable which is needed in any home, i.e. a thermo-hygro meter which not only give you average temperature and relative humidity of any indoor space but the variation of these two parameters in any time duration which depicts the variation to see how these parameters change and enable us to draw conclusions for ourselves about the degree of the comfort of our environment. The only thing that is perhaps a little bit difficult to provide is MATLAB software which should be installed on your PC or laptop, in my case I used MATLAB version 2015b, I think other MATLAB versions could be used and I have tried it on 2013 version successfully , the reason I used MATLAB is its powerful GUI which enable one to publish the results and graphs even for scientific purposes. Another thing, I used Arduino UNO in this project and I am sure other types of Arduino could be utilized, albeit UNO is the most popular type and many hobbyists could easily work with it, as you know Arduino is not only open source but there are thousands of documents and educational videos produced for it and is ideal for DIY projects. Last but not least this device work with a rechargeable battery so a charging jack is incorporated in this project, I have tried my best in order to explain clearly this project to enable other people to make it at home.

The materials used in this project could be bought easily because apart from Arduino Uno other components are available in most electronic or hobbyist shops and also could be purchased in Internet, the Arduino Uno should be bought from a reliable sources because I have bought some colones of that which are not giving right results while it could work apparently without a problem.So the bill of materials are as follows:

1- A cylindrical box say a body cream container with the dimensions big enough for a Arduino Uno in my case I was lucky because my nephew gave me an empty box of CS supplements which is big enough to contain an Arduino Uno, in fact the shear largeness and good appearance of this box encourage me to do this project!

2- A piece of PVC pipe with enough diameter (say 1.5 inches) to contain a 9 V battery and its holder (which is a piece of electrical duct), this pipe could be painted to any color to look good and compatible with the container color in my case green.

3- A cap, in my case I've used a plastic milk bottle cover suitable for capping 1.5 inch PVC pipe.

4- One Charging socket jack.

5- One small SPST switch

6- One 9 V Clip on Type Battery Snap Connector Lead Wire Plastic Head

7- One rechargeable 9 V battery

8- Breadboard jumper wire pack

9 - A small piece of perforated board (1 inch* 1 inch)

10- A 16 x 2 Characters LCD

11- DHT11 Humidity & Temperature sensor

12- 5 k and 10k resistors

13- Arduino UNO

14 - A-to-B USB cable

We need two software 1) the software to drive Arduino UNO and 2) the software to drive MATLAB and plot the live data

1- The soft ware to feed the Arduino should be uploaded through Arduino IDE and is included

2- The software to plot the live data are also attached here.

First you should upload the Arduino software to the Arduino, and after the completion of project you could first make a script file in MATLAB and after the installing Arduino in your PC or laptop find the name of serial port in the device manager of your computer and then correct the script file and replace the serial port number in the program, I recommend to check this two software when you are testing your circuit in bread board stage to correct in early stages of the work and after soldering correction would be difficult and time consuming.

The tools needed for this project are as follows:

1- A Soldering Iron

2 - A drill

3 - A cutter

4- glue

Making this project has two part first which are as follows:

1- Mechanical part would be as follows:

• Cutting the pipe and making a proper hole in it for the SPST switch and painting it if is needed
• Cutting a circle in the perimeter of the container equal to the diameter of the pipe
• Cutting a rectangle equal to the LCD
• Cutting a circle equal to the diameter of the charging jack on the cap
• Installing the battery holder in the pipe(when it is dried after painting) and fixing it with glue
• Stop assembling the rest of mechanical parts to finish the electronic parts.

2- Electronic part is explained in following paragraphs:

• Using bread board and other components i.e. Arduino, DHT11, resistors, LCD, 9 V battery and jumper wires follow the diagram that is provided, first ensure that the circuit is functioning correctly before trying to assembling it inside the pipe and cylindrical box.
• Use perforated board to solder all parts which were connected together on the bread board, you can solder pins on the perforated board in order to be able to connect them to Arduino, DHT11 and LCD by jumper wires later during assembly.
• Try to assemble the Arduino,DHT11, LCD and perforated board inside the box and assemble SPST switch , battery and charging jack inside the pipe.
• Now continue mechanical assembly by 1) making a hole for the charging jack on the cap, and insert the hooked up components inside the pipe and box, and ultimately connect them together and glue the pipe to the box for final touch.
• Now the position of the Arduino USB input is fixed you can carefully cut an opening on the side of the box for USB cable insertion, try your best to make a neat and accurate rectangle.
• Try to make holes carefully on where the DHT11 sensor is located to enable the free exposure of the sensor to environment.

Now the Thermo-hygrometer is ready for test and connection to computer, by switching on and off you can measure the temperature and relative humidity on the LCD, but when you connect it to the PC or laptop and start MATLAB, and run the MATLAB script then you see the plot showing the variation of temperature and relative humidity on line for any time duration as per the diagram you see here. You can change the appearance of the graph and other things as it pleases you. Remember when the Thermo-hygrometer is switched on and you connect it to the PC or laptop only data is transferred and the power of Arduino is provided by battery but when it is switched off both power and data is provided by the PC. If you have humidifier at home you can test this device with your humidifier and see the temperature and relative humidity variation and draw relevant conclusion.

Arduino is a nice micro-controller with hundreds of applications, the aim here was to show how compact and applicable but in the same time accurate instrument can be built at home by simple and cheap components, you can use other more accurate temperature and humidity sensors like DHT22, instead of DHT11, also it is possible to use other kind of sensors for building interesting and applicable instruments like this as an DIY project and not only enjoy but learn a lot of scientific facts by yourself.