Wheel Speed Module 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 module aims to read one/two digital signals and process thesignal in order to obtain the instantaneous speed of the wheel to later send the value to the CAN communication bus of the formula. In the module developed as it is to be integrated in a vehicle to compete in the formula student event, the whole system was designed with the aim of being as compact as possible.

Supplies

• AT90can128
• MCP2562
• MIC5209
• MCP2221A
• Micro USB Port

Step 1: Design

The module is powered by the vehicle's 12V battery in which the current will pass through a diode for protection and the 12V to 5V. For the CAN bus communication, the tranceicer MCP2562 was selected because it allows the selection of the logic communication voltage with the microcontroller.

2 smd leds were added in order to debug the module in which one led is dedicated to the 5V power and the other one to the CAN 0 bus.

Since this project presents a need for microcontroller with some processing capacity to achieve the objective of writing in the CANbus. For this, the AT90CAN128 microcontroller was selected, which satisfies all needs.

Step 2: Prototyping

Before proceeding with the manufacture of the PCB, the developed schematic was tested on breadboard in order to validate it to make 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 and a CAN module to send information and simulate the vehicle's communication bus.

Step 3: Design PCB

Taking into account the application of this module, since it is to be in the formula type vehicle, there was a need to develop the PCB with the smallest dimensions possible. For this purpose, very small sizes were defined for the thickness of the PCB tracks (0.18mm) and tracks (0.35-0.7mm) in order to save space and the components were positioned in order to minimize the free space on the PCB. As a final result, the PCB shown in the figure was obtained with the following dimensions 45x24 mm.

Step 4: Ordering the PCB

We choose the JLCPCB because offers fast, high-quality service at reasonable prices.

1. To order visit https://jlcpcb.com/RAT

2. Click quote now button 3. Click on the “add your gerber file” button and upload your gerber files Now you can set your parameters and customizations, such as quantity and PCB colour;

4. Click “SAVE TO CART”;

5. Go ahead and type your shipping address, choose the shipping method;

6. Process to submit your order and payment;

7. The PCBs our team ordered came within the week.

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.

Then is welding carefully every component to the PCB and test to evaluate if everything works fine :)