Introduction: Monitoring of Temperature and Humidity

Hi everybody. We are a group of four people in engineering school. During the long project 2 of the second half-year we were brought to realize a subject of project in a group among the subjects proposed by the professor. Our choice concerned to the Monitoring of temperature and humidity in the TP rooms with an autonomy of energy. The project consists in measuring the temperature and the humidity for every room thanks to a sensor whom it is necessary to define, the spicy values will be visualize on the platform "Actoboard" then managed on a web site.

The purpose of this project is to create a connected system, of measuring temperature and humidity in a room. This system has to have a low energy consumption, it will thus be necessary to find a compromise between the production cost of the system and the energy consumption of the components which will be used. The communication enters the snootlab card and the akeru waiter will be assured via the protocol Sigfox. The values of the temperature and the humidity can be visualized in the form of curve on the associated platform. The information will be passed on automatically once a the hour what implies that we are going to use 24 send a day on 140 licences days by the standard of the communication Sigfox what makes a total of 96 messages by.

Creation of an Internet site equipped with a laboratory room plan and in which the temperature and humidity values detected by the sensor will be visualized.
We also carry out a study of adding a solar panel to recharge the battery and a brightness sensor. The system designed will be inserted in a housing so that it is easily transportable. Finally, a push button add in order to be able to switch on or off the system.

Step 1: Material Needed

To build this project you will need:

1. PowerBoost 500 Basic - 5V USB :

It allows to provide a feed of 5V with a battery(drum kit) of 3.7V - 1050mAh. The 5V will allow to feed all the system, it will be possible to make an energy control at this level. Cost of the component : 9,35 €.

2. Adafruit Micro Lipo :

Allows to reload the used battery (drum kit). Connect to an USB port of the P.C or via a sector U.S.B. Cost of the component : 5.95€.

3. DHT11, sensor of temperature and humidity:

Allows to measure the temperature and the humidity detected. The measure will be made at least every second, sends him(her,it) will be made only via the permission of the microcontroller who will be used. Use a port(bearing) Pine 8 to pass on(to transmit) the measures to the module Snootlab. Feed 5V via the dough Wine which goes to the regulator. Cost of the component : 5,20 €.

4. Base Shield V2 :

Allows to connect the sensor DHT11.
 Connects to the microcontroller. Cost of the component : 8,30 €.

5. AKERU beta 3.3 :

 Will be used as microcontroller for the system. Send data via the module of the card. Cost of the component: 55 €.

6. Lithium rechargeable batterie

Will be used to feed the system. Fed there 3.7V. Cost of the component 8.60 €.

7. 3W Solar Panel 138X160 :

Will be used to recharge battery. Fed there 5.5V and supplied a power of 3W. Dimensions: 160x138 mm. Cost of the component 12.80 €.

Step 2: Send / Receive Measurements

First of all it is necessary to power the card in 5V and put a resistance of 1 ohm in series with the card in order to measure the voltage at its terminals which is in fact the current consumed by the card.

The measurements are made with an oscilloscope.

Once we receive measurements on the oscilloscope, we must write the sending codes on the Actoboard website. The measurements are sent via SigFox.

Step 3: Recharge the Battery

1. Refill by solar panel:

The battery that powers our system is 6 days. In order to recharge it we think using solar panels that provide 3W in full sun.

Our system consumes a total of 1W and 1W battery, which makes a total of 2W. Our solar panel should provide us with a maximum power of 2W. We therefore test our solar panel to see if it provides us with the necessary power under the ambient light of the TP rooms.

For this test we measure the voltage at the edge of a resistor wired in series with the solar panel. By varying the values of the resistors, one obtains the values of the table that you can see in the photograph.

Conclusion: we will not use the solar panel to recharge the battery because it provides maximum 3mW. We will therefore study a recharge of the battery thanks to the induction charger.

2. Induction refill:

It is desired to implement a wireless power supply, for this purpose:

A transformer is used 230V => 5V 500mA A DC / AC converter is made via a bridge in H = 0 / 5V square signal at the output This square signal is passed in a resonant RLC circuit, in order to have a larger reception voltage. On reception, a coil is recovered which recovers the voltage directly and then a diode bridge is added. Finally, a voltage recharger with a smoothing capacity is integrated to have a 5 V output signal which will allow the battery to be recharged thereafter.

Step 4: Creating a Website

Our system being a connected system, we decided to create a site. You will find above pictures of our codes.

We will not put the link of our site on this tutorial because we have a free trial on bluemix of 1 month. However, if you want to see the values of our monitoring you can click on the link below: