PS9888 | Self-Cooling Jacket

Our group consists of Anh, Flora, Christie and Qi Rui. We are a passionate group of people and seek to bring comfort to people via our inventions.

We constantly refine our ideas to create the coolest jacket ever imagined.

Description
This project presents a self-cooling jacket that uses conduction as method of cooling the wearer. There are sensors embedded into the jacket which increases its functionality. Sensors include Flex and Temperature sensors.

Vision
Our project aims to help those engaged in strenuous activities or exposed to the heat. By cooling down the wearer’s body temperature, it reduces health risks associated with heat.

 Initial Phase

Overall design

It contains the battery power supplies, providing power to the ESP32 and logic level convertor which in turn powers the motor driver. The ESP32 micro-controller gets temperature data from temperature sensors and uses that data to regulate the temperature in the cooling system. This is done by varying pulse width modulation signal to a motor driver, which then varies the voltage on the peltiers, with Potential Integral Derivative control. Other sensors include flex sensor. A logic level convertor converts the 3.3V from the ESP 32 into 5V for the motor driver. A telegram bot displays the information. This modular approach allows for the addition of more functions and sensors in the future. 

Cooling system

The preliminary design for the cooling system is as shown. Each peltier is going to be sandwiched between a blower and a copper plate. A peltier is a device that has two dissimilar conductors, causing one side to be cool and the other side to be hot. So, one blower will take in air from the surrounding and pass it through the hot side of the peltier and then releases it to the surrounding again, thus removing the heat. For the cooling, a copper sheet will be cooled by the cold side of the peltier and therefore reduce the temperature of the wearer via conduction.

Final Product

Final Product images/videos with descriptions.

How peltier works

A peltier has two dissimilar conductors, causing one side of the peltier to be hot, while the other side to be cool. By allowing the cooler side of the peltier to cool the copper sheet, conduction and convection currents will cause the temperature of the air in the jacket to be reduced. Heat will be dissipated from the other side of the peltier using a DC fan and heat sink, such that heat would not be transferred to the cool side of the peltier and affect the cooling process.

How is the temperature of the peltier regulated

Temperature sensors will be attached to the hot and cool side of the peltier to monitor the heating and cooling process respectively. The temperature measured of the cool side of the peltier will be used as an input for Proportional Integral Derivative (PID) control. Should the temperature difference between the setpoint and the input be large, the current supplied to the peltier would be increased to enhance the cooling process. The PID coefficients will also be modified to optimise cooling. When the temperature of the input and setpoint is the same, current would be reduced to maintain the temperature of the peltier.

ESP32 

Our ESP32 can perform together with our host MCU, reducing communication stack overhead on the main application processor. It can interface with other systems to provide Wi-Fi and Bluetooth functionality through its SPI / SDIO or I2C / UART interfaces.

Flex sensor

When the substrate is bent, the sensor produces a resistance output correlated to the bend radius—the smaller the radius, the higher the resistance value. This is used in our jacket as a posture correction mechanism, where the user is reminded to sit upright when the curvature of the back reaches the threshold.

Embarking on this journey exposed us to different aspects of making a prototype, such as circuitry, coding, 3D printing, soldering, planning for housing design and many more! Out of it, we acquired many problem solving skills, such as debugging and working out the many problems that came our way.

As we were very interested in creating a smart jacket with many functionalities, we learnt and tested on many sensors such as heart rate sensors, flex sensors, IMU sensor and thermal sensors. We also tried with UV sensors but those sensors were faulty. Overall, it was a challenging yet eye-opening experience!