Introduction: Final Prototype - COVEX
This device is in charge of storing vials containing Covid-19 vaccines. The main goal of this design is keeping the temperature inside the desired range (2 - 8°C) while keeping its contents safe from impacts and vibrations that might occur during transportation through long periods of time (approximately 8 hours).
This device's manufacturing process is divided in two parts: the container and a system in charge of monitoring the temperature inside of it. Due to this division, the first part will contain the instructions required to manufacture the container and the second part will deal with the construction of the system in charge of monitoring the temperature.
MDP wood: 11 boards 1.5 cm thick with the following measurements:
- 3 units 41cmx41cm
- 2 units 41cmx38cm
- 2 units 32.7cmx30.1cm
- 2 units 30.1cmx 29.7cm
- 1 unit 38cmx38cm
- 1 unit 32.7cmx32.7cm
MDF wood: 9 units of 29cmx30cm, 2 mm thick
Foamy: 1 sheet of foamy
Screws: a pack of 100 wood screws
Velcro: 1 meter
Polyurethane: 750ml polyurethane foam x 2
Dry ice: 2 kg
Hinges: 2 units
Temperature Monitoring System:
Protoboard: a 700 point protoboard was used, but a smaller one may be used in order to reduce the space occupied and the system's weight.
Arduino UNO R3
Batteries and adapter: 6 AA batteries and an adapter for them (see pictures in the manual)
LED: red or similar
5 V Buzzer
Male to Male jumper wires: approximately 20 wires are required, but it is recommended to have more because some might be lost or damaged while stripping.
Temperature sensor: a waterproof DS18B20 sensor was used.
Scissors: optional, but recommended.
Wire Stripper: optional, but recommended.
Resistor: two approximately 100 Ohm resistors are needed.
Step 1: Exterior Box
This step consists mainly in the construction of the exterior box of the system. The result of this step will be a cubic box of five faces, as seen in the second image.
The first step is to arrange each individual piece of wood as shown in the first image. To do this you will have to select one piece of wood to be the base of the box. Then you will have to locate 4 pieces of wood around the base, one for every side. This step will gaurantee that all the sides of the box fit correctly.
Then, one member of the team will have to hold one wall of the box perpendicularly to the base. At the same time, another member will be encharged of applying the glue between this two pieces of wood, the wall and the base. Is recommended to wait approximately 5 - 10 minutes for the glue to be completely dry. Once this time has passed, you will have to attach three screws in the face of the wall, each screw at a distance of approximately 10 cm. You will have to make sure that these screws pass through the wall and the base of the box. You will have to repeat this procedure for each of the 3 remaining faces of the box.
Afterwards, you will have to attach 2 screws between two faces of the box. These screws should 10 cm apart, you must assure that the screws secure correctly this two faces. This procedure must be repeated for the remaining faces of the box.
Step 2: Interior Box
The process followed for building the internal box is the same as the one for the for the exterior box, but in a lower scale. The only difference is that the distance between each screw will be of 7 cm approximately.
Once the interior box is completely built, you will have to select three interior faces of the interior box. One of this faces must be the base of the interior box and the other two must be opposite faces. Then you will have to attach 2 screws on each of the selected faces, these screws must be 3 cm apart from the edge of the interior faces of the box and 5 cm apart from each other. Once this step is done, you will have to repeat it four times, but this time you will need to leave a space of 5 cm between each row of screws. The result of this process is four "rows" of screws that will hold the trays of the device.
Step 3: Application of the Polyurethane Foam
For the realization of this step is really important that all the members involved read and apply the precautions specified in the polyurethane foam can.
First, the exterior box needs to be placed as shown in the figures, with the base touching the floor. Then one member of the team must make a line that passes through the four interior walls of the exterior box. This line must be 5 cm apart from the base of the box and will act as an indicator for the application of the polyurethane foam. This line can be made with a permanent ink marker or tape.
Once this step is done, one member of the team wil start applying the polyurethane foam inside the exterior box. This process shall stop when the polyurethane foam covers the 5 cm indicator. Then, another memeber of the team must place the interior box inside the exterior box, this memeber must assure that there is a space of 5 cm between the faces of the interior and exterior box. After making sure that the internal box is correctly placed, you will have to continue applying polyurethane foam on the missing spaces between the internal and external box. The member encharged of the polyurethane foam application must assure that there are no gaps missing.
Is recommended to wait approximately 24 hours until the polyurethane is fully expanded and dried. After this period of time, is neccesary to cut the surplus of polyurethane formed by the process of expantion. You can use any type of cutting tool for this process, but you have to make sure that the cuts match the edge of the box.
Step 4: Assembling Trays
For the construction of the trays it is necessary to cut the holes where the vials will be placed, these must have a diameter of 25 mm and have a spacing between them of 5 mm, it must be as shown in the image. To join the base to the top, it is necessary to cut one of the boards into strips 3 cm wide and long enough to surround the perimeter of the boards. The cut strips are glued to the boards that will serve as the base, which are the boards without making any cut and should be like the second image, wait for them to be firm and on this the boards with holes are glued and again wait for that I know what. This must be repeated until 3 of these trays are obtained.
For the upper dry ice tray, it is only necessary to carry out the procedure up to the second part, without the need to glue a board on top.
After the polyurethane is cut flush, foamy is glued over the area between the two boxes in such a way that it covers the polyurethane and the edges of each box, as seen in the first image.
For the closing mechanism a velcro strip is used, this is cut long enough to pass through the right side and reach the door. A strip with the two parts is screwed on the right side, with the longest part of the hooks. Only one strip is screwed onto the door with the opposite side to the hooks. This should look like the second image.
Step 6: Door Installation
This step consists of assembling the device door. For this, it was started by screwing two hinges on the same face of the external box, two screws were used for each hinge. Once this was done, the door was screwed on using the same hinges, two screws were also used for this.
Step 7: Building the Temperature Monitoring System
Next, the instructions on how to build the temperature monitoring system will be presented. The image on top shows the overall appearance and features of it.
Step 8: Adapting the Temperature Sensor
This step is to adapt the sensor in a way that will allow it to be connected to the protoboard.
When looking at the lower end of the sensor (opposite side to the part that will measure the temperature) you will find three small wires coming out of it. One of them will be red, another will be black and the remaining one will be yellow. The purpose of each of them is the following:
- Red: voltage input (3 - 5.5 V)
- Black: ground
- Yellow: signal output
You will notice that the wire's ends will be stripped (the metal is exposed), which isn't suitable for connecting them directly to the protoboard. Because of this, you will need to cut and strip the end of one of the male to male wires and join it to the exposed ends of the sensor wires. Once the ends of both cables are joined, electrical tape must be placed in the place where the wires are exposed.
The image that appears on top summarizes this process.
Step 9: Adapting the Power Source of the Circuit
This step is exactly the same as the last one, but this time will be used to allow the battery adapter to be connected to the Arduino board.
You will find two wires in the battery adapter which have the following purpose:
- Red: voltage output
- Black: ground
The image on top shows the final result of this step.
Step 10: Connecting the Temperature Sensor to the Protoboard
Now that the sensor has been adapted, we can connect it to the protoboard.
Each one of the wires must be connected to a different row and one of the resistors must be connected between the yellow and the red wire. Connecting the resistor appropiately is very important since failing to do so will cause a short circuit that can damage the sensor or be dangerous since the sensor will get very hot.
NOTE: the resistor shown in the image is for illustrative purposes and does not necessarily correspond to the recommended values.
Step 11: Supplying Voltage to the Temperature Sensor
We will use the 5V pin form the Arduino board in order to supply the required voltage to the temperature sensor. This will also be used to power the other components of the circuit.
A cable must be connected to the 5V pin of the board and then the other end must be connected to the row in which the voltage input of the sensor (red wire) was placed in the previous step. This process also has to be done with on if the GND pins of the board, which has to be connected to the ground (black wire) of the sensor.
Finally, another wire must be connected to the signal output of the sensor. This has wire must also be connected to the pin number 12 of the board.
The image included on top allows to see this configuration. The red wire comes from the 5V pin and the black wire comes from the GND pin (note that the wire connecting the signal output of the sensor to the board is missing).
Step 12: Implementing the LED Alarm
This step allows to implement one of the two alarms that will be given in the case that a temperatura outside the desired range is detected.
The LED must be connected to the protoboard having in mind the row in which its longer terminal was plugged (you will notice that one of the ends of the LED is longer). The row in which the shorter terminal was placed must be connected to ground (you may get the ground using the row in which the ground of the temperature sensor was connected). The longer terminal must be connected to one of the terminals of the remaining resistor (the other one was used when connecting the temperature sensor). The other end of the resistor will be connected to a completely unused row of the protoboard and a wire that comes form the pin number 6 of the Arduino board must also be connected to this row.
The image on top shows this configuration. Observe that the blue wire on the right hand side of the picture corresponds to the wire that comes form the pin number 6 of the Arduino board.
Step 13: Implementing the Sound Alarm
The other way in which the user will be notifed when a temperature outside of the desired range is detected is through a sound alarm. This step has the purpose to implement this part of the circuit.
The buzzer must be connected keeping in mind the row in which the voltage input of the device was placed (this is usually indicated on top of the buzzer with a "+" sign). This row must be connected to the pin number 7 of the Arduino board and the other one must be connected to ground.
The image on top allows to see this configuration. Keep in mind that the blue wire is the one that comes form the pin number 7 of the Arduino board.
Step 14: Uploading the Code to the Arduino Board
In order for the temperature monitoring system to work, some code must be uploaded to the Arduino board. This code allows the temperature to be read by the board and the alarms to be activated when necessary.
The Arduino board must be connected to a computed and then the code that contained in the file "Sensor.ino" must be uploaded.
NOTE: this code uses some libraries that do not come by default when the Arduino IDE is installed. Thus, you must downloaded them before trying to upload the code to the Arduino board.
The libraries that must be installed are the following:
- OneWire: the author list begins with Jim Studt and ends with Love Nystrom.
- DallasTemperature: its creators are Miles Burton, Tim Newsome, Guil Barros and Rob Tillaart.
When searching the libraries' names, more than one option may appear, which is why the creators' names were mentioned. Care must be taken when selecting which library will be installed.
Step 15: Connecting the Power Source to the Arduino Board
The last step consists in connecting the battery adapter to the Arduino board. This will allow the circuit to work without the need of being connected to a computer, which is crucial for its practical use.
First of all, the Arduino board must no longer be connected to the computer, and the cable used for this must be completely unplugged. Once this has been done, the voltage output of the battery adapter (red wire) must be connected to the "Vin" pin of the Arduino board and thr ground of the battery adapter (black wire) must be connected to one of the GND pins.
The image on top allows to identify the position of the Arduino's pins mentioned before.
NOTE: some adapters allow to turn on or off the power supply. When connecting the adapter, you must make sure that the power supply is "on"
Step 16: Monitoring System Installation
To install the system it is necessary to screw two velcro strips in one of the corners of the upper part of the device, then the opposite side to the breadboard and to the arduino is glued with silicone. To insert the sensor, a hole is made approximately in the center of the upper part of the device until it reaches the internal part of the device.