Hardware Reference
In-Depth Information
are two parts: a thermistor to measure the temperature and a humidity sensor. A chip in-
side the sensor does all the analog-to-digital conversion. It is really convenient to use with
Arduino and comes with a nice Arduino library.
There are actually two versions of this sensor: DHT11 and DHT22, the second one being
more precise. You can use the version you want; you'll just have to change one line of the
code. Along with the DHT sensor, you will need a 4.7k ohm resistor for the sensor to
work correctly. This is necessary to create a pull up on the data line. We will see how to
insert this resistor in the next section. You can learn more about these sensors at the fol-
lowing URL:
You can also use a sensor of your choice, or even two separate sensors. You can use, for
example, an analog sensor for the temperature and a digital sensor for humidity; it's com-
pletely up to you. You will just need to make sure that these measurements end up in the
correct variables in the Arduino sketch.
To make connections between different components, you will also need a breadboard and
some jumper wires. You will also need a 10 uF polarized capacitor to program the Ardu-
ino board via Bluetooth. Indeed, one of the cool things about this kind of Bluetooth mod-
ule is that it acts as a serial port just like USB, so you will be able to program your Ardu-
ino board wirelessly. A capacitor is needed to do that, as it will be used between the
Bluetooth module and the Arduino board to drive the reset pin and set Arduino into the
programming mode.
The following is a list of all the components that were used for this project:
• Arduino R3 board (
http://www.adafruit.com/products/50
)
• Bluefruit EZ-Link Bluetooth module (
http://www.adafruit.com/products/1588
)
• DHT11 sensor and resistor (
http://www.adafruit.com/product/386
)
• 10 uF capacitor (
https://www.sparkfun.com/products/523
)
• Breadboard (
http://www.adafruit.com/products/64
)
• Jumper wires (
http://www.adafruit.com/products/758
)
Note
Because of this last point, you don't actually have to plug the board via USB. You
can simply use an external power source, such as a battery, to power the Arduino
board.
