Infrared Tire Temperature Sensor for Formula Student

Background:

Formula Student the world most established educational engineering competition which uses motorsport to inspire students.

Backed by industry and high-profile engineers such as Patron, Ross Brawn OBE, the competition aims to develop enterprising and innovative young engineers and encourage more young people to take up a career in engineering. The format provides an ideal opportunity for students to demonstrate their engineering knowledge and test and improve their capabilities to deliver a complex and integrated product in the demanding environment of a motorsport competition.

Objective:

The tire temperature acquisition module aims to measure the tire temperature at three points, namely at the inner and outer ends of the tire and in the center. To perform the measurement, the MLX90620 infrared temperature sensor was used, which has the ability to acquire the temperature in 64 points distributed in a 16x4 pixel matrix. This sensor, as mentioned, performs the measurement of the infrared temperature, sends this information to the microcontroller through the I2C communication protocol and the microcontroller in turn, through a CAN transceiver, sends the acquired information to the car's CAN communication bus.

Supplies:

• MLX90620 temperature sensor;

• SPI-CAN MCP2515 transceiver;

• MCP2551 CAN transceiver;

• Voltage regulator 12V-5V MCP1755_5;

• Voltage regulator 12V-3V MCP1755_3;

• Standalone Atmega328P microcontroller.

Step 1: Design

The module is powered at 12V via the car battery. The 12V-5V regulator is used to convert the module's supply voltage to a 5V level to supply the microcontroller and CAN transceivers. Since the temperature sensor operates at a voltage of 3V and not 5V like the other components, a second voltage regulator of 12V-3V was used to supply the sensor.

Tire temperature measurement is performed by the sensor in a 16x4 matrix that is sent to the microcontroller through the I2C communication protocol. The microcontroller was programmed in order to receive this matrix and perform the calculations to convert it into just 3 temperature points considered relevant, namely the ends and the center of the tire. Once the 3 temperature points are calculated, the microcontroller sends these 3 data via SPI to the SPI-CAN MCP2515 transceiver, and this to the CAN MCP2551 transceiver, which provides the information on the car's CAN communication bus.

Step 2: Prototyping

Before proceeding with the manufacture of the PCB, the schematic developed was tested on a breadboard in order to validate it in order to be sure that the module would work as intended. For this, the schematic was mounted on a bench where an adjustable power source was used to simulate the car battery and power the module. In order to validate the correct operation of the sensor, several objects were used as targets of the temperature sensor and a thermographic camera to validate the temperature acquired by the sensor. To validate the information processing by the microcontroller, a second prototype was used to operate as a CAN receiver that allowed us to read the information sent by the module to the CAN bus, verifying the correct functioning of the developed module.

Step 3: Design PCB

Taking intoaccount the application of this module, since it is to be implemented next to the wheel of the car, there was a need to develop the PCB with the smallest possible dimensions. For this purpose, very small sizes were defined for the thickness of the PCB tracks and tracks in order to save space and the components were positioned so as to minimize the free space on the PCB. As a final result, the PCB shown in the figure of dimensions 48x12 mm was obtained.

Step 4: Ordering the PCBs

Now we have got the PCB design and it’s time to order the PCB’s. For that, you just have to go to JLCPCB.com, and click on “QUOTE NOW” button.

JLCPCB are also sponsor of this project. JLCPCB (ShenzhenJLC Electronics Co., Ltd.), is the largest PCB prototype enterprise in China and a high-tech manufacturer specializing in quick PCB prototype and small-batch PCB production. You can order a minimum of 5 PCBs for just $2.

To get the PCB manufactured, upload the gerber file you downloaded in the last step. Upload the.zip file.

PCBs were well packed and the quality was really good.

Link: https://jlcpcb.com/

Step 5: Assembly

As the last step of this process, after receiving the PCBs sent by the manufacturers and gathering all the necessary components, the final assembly of the modules for implementation in the car was carried out, as shown in the figure.