Temperature Sensor
For EK131 I created this project. The motivation for doing this project was to gain an understanding of some of the skills and processes that will be used in applied engineering. The main skills applied in this project were 3D modeling, 3D printing, wiring, measuring current and voltage, and coding in c++. The aim of this project was to make a functional box that is able to sense the temperature and display it on the screen along with the buzzer playing a sound and a light flashing if the temperature is between 22 - 24 degrees celsius. The report is made to describe the process of making the box along with the design elements of the box.
Design process of room temperature monitor
Madeline Malloy U36399505
Summary:
The purpose of this report is to describe the making of the temperature sensing box. The creation and steps of making this box deeply inline with the class work and home work of this course. We began the process by making a 3D model of the box on Onshape. We then proceed to cut holes into the box, laser cut the mounting plate, and 3D print the battery holder. Finally we created wiring and code for the arduino and placed it into the box. In the end I created a box that is functional and matches most of the initial design. The buzzer and LEDs are placed in a straight line perpendicular to the side of the switch. With this project we have shown how to find the temperature using the temperature sensor, how to display temperature using the LCD screen, and create a song using a buzzer.
Design Elements:
Components
ABS enclosure (view figure )
Arduino board
Switch
Buzzer
Temperature sensor
LED
Mounting plate
Battery holder
2 resistors
Variety of 22 AWG and jumper wires
Precision measurements
Refer to Figure 1
Purpose of Arduino Board
The purpose of the Arduino Board is for control and to convert analog signals to digital signals. We wouldn’t be able to implement our code the way we did without the arduino board.
Wiring diagram
Refer to Figure 2
Solder LED and resistors together
Switch connected by spade connector
The buzzer was soldered onto a board and the wires were attached to the board
LCD screen used jumper wires
Nothing was soldered to the arduino board (however ends of wires were soldered to make interesting them easier )
Shrink tubing was used to cover all soldered parts. When LEDs were replaced when they were burnt out they had shrink tubing wrapped around them and electrical tape to make sure no parts were exposed.
Specify wire gauge
Jumper wires 28 AWG (226 mA) was used for data and 22 AWG for power. While the maximum current drawn in their circuit is less than 100 mA, the maximum current for those wires can handle from the ampacity table is 920 mA. The jumper wires could cause issues with the arduino. The 22 AWG wires are good for power and for the Ardino because it fits nicely, and the core handels a good amount of current for this circuit. The green LED has a resistor in series that's 1000 Ohms, and the red LED has a resistor that's 220 Ohms. The operating current for the green LED is 9v/1000 Ohms and the red is 5v / 220 Ohms.
Internal power supply
The 9-V battery was used because it had enough power for what we were doing, and its shape was easy to work with. Along with this the arduino accepts voyages between 6-20V. 9V is safely in this range. The charge capacity of a standard disposable battery is 1200 mAH. 1200 mAH/ 77.2mA so this should work for around 15 hours and 30 minutes. This is a good option if it’s something you will only turn on once in a while. You can power the device externally by plugging it into your computer.
Code
Reference Figure 3.
Specifications of prototype
The battery provides 9.2V. The total current drawn is 77.2mA. The comfortable range of the temperature sensor is room temperature. The temperature range of the sensor is -40 to 125 degrees Celsius. The operating voltage of the circuit is 5v. The green LED is brighter than the red LED and using KVL we can see that red has less current going through it so despite having less resistance the red LED is dimmer. As stated before the operating time with one battery should be around 15 hours and 30 minutes.
Evaluation of Results
Box was successfully made. The temperature sensor tends to give a number that's less than the temperature of the room. I question if the temperature sensor touching the box is making it colder. Possibly insulating it somehow could increase the accuracy of the results. The box size was convenient for wiring but is larger than other thermometers and is impractical. There is also unused space at the top making the box taller than it needs to be. To improve the design we could possibly make a way to easily remove the battery from the box without removing the top. Or possibly making the box attach to an outlet. This is because the battery life makes it impractical to have the box on all the time. Along with this the weight of the box is a bit high, but shouldn’t be an issue if mounted on a stable wall. Overall for a temperature sensor it does its job.
Supporting materials
