2. Methods

2.      Methods

2.1    Equipment

For the Arduino:
- DHT11 basic temperature-humidity sensor x1
- Arduino Black (Leonardo Model) x1
- USB cable x1

To make the dehumidifier:
- Computer fan (12 cm x 12 cm, 480 V)  x1
- Glue Guns x2
- Tubes x 2 meters
- Nuts and Bolts x1 packet
- Hair Dryer (220 V -240 V) x1
- Duct Tape x1
- Plastic box x1
- Drill x1
- Swiss Army Knife/ Pen Knife x1
- Saw x1
- Screwdriver Set x1

To make desiccant wheel:
- Tin Box (20.6 cm x 20.6 cm x 6.5 cm)
- Flour sieve x2
- Motor x1
- Premium Silica Gel (Drying Agent), 500 gm x2 bottles
- Nuts and Bolts x4
- L-shaped brackets x4
- Aluminium plates 20.5 cm x 2.5 cm
- Wooden blocks x 4
- Wooden Rod x1
- Rubber belt x1


For the testing:
- Digital Thermo-Hygrometer x 2
- Wooden Box (70 cm x 70 cm x 72cm)  x1
- Cling Wrap x 1 roll


2.2    Diagram
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Figure 2.2.1 - Desiccant Wheel

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Figure 2.2.2 - Front view of dehumidifier

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Figure 2.2.3 - Back view of dehumidifier

2.3    Procedures

1) Building the desiccant wheel :
a) Drill a hole in the center of a round tin box.
b) Glue 4 wooden blocks to the base of the round tin box, using hot glue guns, in a spiral pattern around the wooden rod. Paste duct tape around the wooden blocks or any sides to prevent gaps for air to escape or for silica gel to escape.
c) Draw out 4 holes in each of the partitions to be cut at the bottom of the round tin box.
d) Cut out the holes using a hammer, a nail and snips.
e) Using a pen knife, cut out mesh wire from a flour sieve. Trace the outline of the 4 holes cut out using a permanent marker and cut out the outlines. Cover the holes with mesh,cut out from the flour sieve, using duct tape.
f) Fill the 4 partitions in the round tin box with silica gel.
g) Cut out mesh wire from another flour sieve using a pen knife. Place it on top of the round tin box and mark out the position of the wooden rod. Cut out a hole where the wooden rod will be placed.
h) Cover the top of the round tin box with the mesh wire [from o)]. Snip the edges of the wire mesh using scissors and then use duct tape to secure the wire mesh onto the round tin box. Hammer nails into the wooden partitions of the to nail the mesh wire to them.
i) Attach a motor with a disc to a bracket. Place a rubber belt around the disc of the motor and the round tin box.

2) Building the structure :
a) Sketch out a detailed diagram of the structure, inclusive of all the required measurements.
b) Cut out a wooden rod of length 7.5 cm.
c) Drill holes in the center of the bottom of square tin box and the centre of the round tin box.
d) Sandpaper the wooden rod so it reduces in diameter and can slide into the holes in the center of the box easily.
e) Cut out two L-shaped aluminium brackets from an L-shaped aluminium plate and drill holes into the brackets. File the edges of the brackets to make the blunt and less risky.
f) Cut out two metal plates (21.5 cm x 21.5 cm) and drill holes into the ends of each metal plate. File the holes to remove the excess aluminium around it [ safety ] and to make the hole slightly bigger.
g) Secure 2 brackets to each end of the two metal plates using nuts and bolts. Tighten the screws using a vice clamp and a plier.
h) Place the 2 metal plates, with brackets attached to them, on the square tin box and mark out where to drill the holes to screw the brackets to the tin box.
i) Drill holes in the places marked out and hand-tighten the metal plates to the tin box to make sure it fits. Unscrew the metal plates from the tin box once made sure that all the holes are well aligned.
j) Cut out 4 circles, each of diameter 4.5 cm, from the back of the square tin box
k) Place the round tin box, with the motor attached, inside the square tin box and align the 2 holes in the center of the 2 boxes with each other.
l) Insert the wooden rod into the 2 holes and then screw the 2 metal plates (from h)) on the square tin box after inserting the wooden rod into them. Tightly wound a rubber band around each end of the wooden rod and tape the rubber band down to make sure it does not slide out of the rod.
m) Ensure that the round tin box is able to be spun by the motor by switching the motor on.
n) Place the entire desiccant wheel in the center of a plastic box.
o) Place the motor a few centimeters away from the round tin box and mark out the position of two holes in the bracket of the motor on the base of the plastic box. Remove the motor before drilling holes in the  marked-out positions. Replace the motor and screw it to the base of the plastic box.
p) Screw the square tin box to the base of the plastic box by drilling holes in both the tin and the plastic box.  
q) Screw steel protections to the back and front of a computer fan.
r) Place the computer fan on the wall of the plastic box such that it faces the front of the desiccant wheel. Trace and cut out the circle of the computer fan. Screw the computer fan to the plastic box such that the front of the fan faces inside the plastic box.
s) Cut the thin end of a funnel of and replace it with a pipe using duct tape. Attach the mouth of the funnel to the computer fan, making sure to cover the entire front of the fan.
t) Tape the pipe [from 4)] to the left side of the metal plates using duct tape such that all the air is directed to the silica gel inside the desiccant wheel.
u) Attach a hair dryer to the right side of the metal plates using duct tape such that all the air is also directed to the silica gel.
v) Cut out an opening in the box for the wire of the hair dryer and the motor to be lead outside the box. Once the 2 wires have been pushed outside the box, seal the opening using duct tape and cardboard.
w) Cut out 4 holes of diameter 4.5 cm in the wall of the plastic box facing the back of the desiccant wheel using a pen knife.
x) Push 4 pipes through the holes in the plastic box and the back of the square tin box. Make sure the pipes do not touch the round tin box. Secure the pipes by taping them the the plastic box and the metal box using duct tape.

3) Building the sensor system:
a) Connect a relay to the desiccant wheel, fan and hair dryer each. Afterwhich, the three items are to be connected to the Arduino using the relay.
b) Connect the arduino-based hygrometer to the same Arduino.
c) Code the Arduino so that it fits all the requirements such that the dehumidifier works automatically.

4) Putting together the entire set-up:
a) Place the entire set-up in a wooden box along with a hygrometer that faces the front. Paste cling wrap on the opening of the wooden box to make sure it is airtight. Cut two holes in the cling wrap and lead the two pipes that blow out hot air from the hair dryer to the outside of the box.
b) Record the humidity level shown on the hygrometer every 15 minutes. Write the results down in a table. Compare the humidity level in the box with the normal humidity levels. If the relative humidity in the wooden box is lesser than the latter, the experiment is a success.

2.4    Risk Assessment and Management
Figure 2.4.1 - Risk assessment matrix

- The sharp blades of the fan.
  • Likelihood : 1
  • Severity : 2
  • Risk : 2
  • This is highly unlikely to occur as the fan compressor will be inside the whole set up. But, while installing the fan compressor inside the dehumidifier the person might get a small cut or a big one which will hurt them. Hence, it will be best to take precautions while placing the fan compressor inside the dehumidifier.


- Hot glue guns
  • Likelihood : 2
  • Severity : 1
  • Risk : 2
  • The glue gun will be used often to stick things together and connect objects. Since glue guns are hot, they can be dangerous if not handled with care. Even though they may easily cause harm to us, the potential severity of harm is not high. Therefore, it will not be very risky. Nonetheless, we will still take precautions and not leave the glue gun unattended and look after ourselves.


- Drilling holes into the metal pieces
  • Likelihood : 3
  • Severity : 2
  • Risk : 6
  • We have to be cautious while drilling the holes into the metal container as we might drill our hands in the process. In order to safely carry out this process, we went to the factory itself to build out desiccant wheel as they have the right equipments and safety gears. We also were supposed to wear goggles for protection of the eyes from the debri of the metal from going into our eyes.


- Sawing of wooden pieces
  • Likelihood : 3
  • Severity : 2
  • Risk : 6
  • We have to be cautious while sawing the wooden parts. Since the saw may cut our fingers or the wooden parts may scratch us. Therefore, we should be very cautious when sawing. While sawing the wood, we used the metal stand to secure the wood in position to allow it to cut properly. We were also told by the employee on how to saw the wood properly. During the sawing of the wood, we were also told to wear goggles for safety purposes so the dust from the wood will not go into our eyes.

2.5    Data Analysis

After building the dehumidifier, we will place it in an airtight wooden box, along with a hygrometer. The hygrometer will allow us to observe the change in relative humidity every 15 minutes. The data will then be recorded in a table. The relative humidity of another room will also be observed and recorded down at a 1 hour interval. The relative humidity of the two set-ups will be then compared. The box in which the dehumidifier will be placed is Box A while the box with only the hygrometer placed inside, which is the control, is Box B. We will conduct 3 experiments (Experiment 1, 2 and 3). Each experiment will be done twice (Experiment 1a, 1b, 2a, 2b, 3a and 3b) to ensure that all the experiments conducted were fair, accurate and reliable.

Using the data collected, we will plot a table of the relative humidity of each room at the 15 minute intervals. Afterwhich, we will compare the two results to find out if the relative humidity in the room with the dehumidifier had decreased and by how much. This will allow us to find out if the dehumidifier works in such a way that it fulfills all of its goals. We will also observe whether the dehumidifier is able to switch on and off automatically according to the respective levels of relative humidity.

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