Green Team Twente – PCB discussion

Green Team Twente

Eurocircuits has been an important partner of Green Team Twente for the last few years. And after Green Team Twente switched to Formula Student last year, our partnership has become even more important. Up until 2022, Green Team Twente has been participating in the Shell Eco Marathon (SEM), with the goal to build the most efficient hydrogen powered car. Whereas in Formula Student, the focus is more on speed and performance. Since we are the only hydrogen powered team at Formula Student, we need some more specialized electronics for the hydrogen system. In this blog, we’ll discuss two of the PCBs: the Fuel Cell Control Unit (FCCU) and the Electronic Control Unit (ECU).

Fuel Cell Control Unit

At the heart of the hydrogen system is the fuel cell. The fuel cell generates power when provided with air (oxygen) and hydrogen. However, some things need to happen before the air and hydrogen can enter the fuel cell. Both gasses need to have certain pressures, flow, temperature and humidity. Since this is a very dynamic situation, an elaborate control system is needed to make sure the entire system is operating as intended. For this purpose, we designed the FCCU (Fuel Cell Control Unit). Its purpose is to monitor temperature, pressure, humidity, and more sensors. And consequently control both actuators like solenoids, relays and valves, and subsystems like the Compressor, DCDC and pressure regulator. To accomplish do all of this, the FCCU supports a lot of I/O. For example, the FCCU has 16 Analog inputs, 10 Digital input/outputs. 6 12/24V outputs, 2 high current output drivers, 2 CAN busses, SPI, I2C and more. Currently more than 80% of all this I/O is used, while the unused I/O is quite useful for temporary sensors or systems.

Electronic Control Unit

The ECU (Electronic Control Unit) is in many ways a twin of the FCCU. It uses the same microcontroller as the FCCU. Which means that it has a very similar software stack. However, it differs in the I/O. While the FCCU is built in mind with flexibility and the ability to expand, the ECU is more purpose built designed. The I/O of the ECU includes Digital pins for the cockpit dashboard, a buzzer for the Ready-To-Drive sound, and more. The ECU is also responsible for the entire cooling system in the car. The hydrogen fuel cell requires a lot of cooling. Therefore, the ECU supports 5 pumps and fans, and more than 5 flow and temperature sensors.

In order to have some data monitoring, we have a system which we call CANota (CAN Over The Air). This is one of the only systems that was also used in the SEM days of Green Team Twente. CANota consists of a server responsible for receiving, parsing and storing messages, and a client in the car responsible for collecting and transmitting CAN messages. With CANota, we have the ability to log and monitor the entire CAN bus in real time. This year, we completely redesigned the client such that it is integrated in the ECU and supports 4G. Giving us the option to drive anywhere, and as long as there is cell service, we will have live telemetry.