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When developing a solar car, a high quality and reliable electrical system is of crucial importance. The electrical system brings a solar car to life and allows it to move, harvest energy, and provide the necessary control and monitoring systems that the drivers and strategists need to race the car as fast and efficiently as possible. Due to our partnership with Eurocircuits, we never had to worry about the quality of our printed circuit boards because we know that they take quality control very seriously. Additionally, the PCB Visualizer environment checks the manufacturability of our designs, which could prevent costly mistakes. Finally, the fast delivery times and the budget that Eurocircuits provides to us, allowed us to make prototype versions which helped to verify and optimise our designs before ordering a final version.
At Top Dutch Solar Racing we aim to develop anything we can in house, partly to increase our performance but mainly because we think it’s very fun, valuable, and rewarding. By doing this, we can have an influence on as many parameters and specifications as we want. Many companies tend to make compromises to maximise their profit and keep costs down, which often results in products that are not designed to be as efficient as they could be. For our cars, we prioritise efficiency heavily over cost, which is why we are often better off designing our own electrical parts, which has the added benefit of us learning a lot along the way. A lot of our designs are inspired by open-source projects, and we value such projects a lot at Top Dutch Solar Racing. A recent example of this is the motor controller that one of our team members has developed for our most recent car (Green Spirit), which is based on the open source VESC project. By developing our motor controller in house, almost our entire electrical system, including the electric motor and the battery pack, have been developed in house by students. The telemetry system that allows for wireless data communication between the solar car and the strategy car is the only missing piece of the system that is yet to be designed in house. Hard working people who design something amazing and decide to make it open source and share it with the entire world to experiment with, is something that has inspired our team throughout its existence. Which is why one of our team members who developed the maximum power point trackers (MPPT’s) for Green Spirit has decided to launch his design as his own open-source project!
Open Source VESC Based Motor Controller
In Top Dutch Solar Racing’s first car (Green Lightning), the motor controller was still a part that was bought. While searching for and trying different controllers for our new motor/car, we realised that there are no controllers available on the market that really meet all our needs and wishes we had. This was largely due to our supply voltage and efficiency requirements. That’s when we decided to try a different approach and take up the challenge of designing our own motor controller!
While researching this topic, we soon realised that it would be really hard to design the hardware and software in just one year. So, while looking for different options we found out about an open-source project that featured the hardware and software of a motor controller, called VESC. With software that is highly contributed to by a large community and features an easy-to-use tool, we could get all the features and specifications we wanted by designing our own hardware. We concluded that making a design based on this project would be the best option to complete such a project within a limited time. With this idea we went to the drawing table and started prototyping. This resulted in a controller that consists of two PCBs that are stacked on top of each other. One part being the logic board which is a 6-layer PCB that takes care of the processing part of the controller and does all the measurements and calculations. The other part being the power board which is made from an aluminium substrate board that takes care of the power switching and is mounted directly onto a heatsink that passively dissipates the generated heat to the fresh air in the wheel well. After a few prototypes and lots of testing the project can be concluded as successful as it was used in the 2021 Moroccan Solar Challenge to climb the Atlas Mountains without any problems!
Open-Source Maximum Power Point Tracker
The idea to develop an MPPT started back in 2017, based on open-source hardware. The conclusion was quickly drawn that custom hardware needed to be developed for the solar car. Sadly, the project needed to be discontinued in 2019 because of the time pressure associated with building a solar car. Luckily there were good alternatives readily available.
The project was continued in 2020, after competing in the Bridgestone World Solar Challenge for the very first time as a team. Now there was enough time again, the MPPT was developed for the next car. It made its debut in the Moroccan Solar Challenge in 2021. Employing GalliumNitride transistors, the MPPT had a high efficiency of more than 99 percent. With that, improving upon the MPPTs that were used as a backup in 2019.
Eurocircuits helped a lot during the development of the MPPT. Over the years, 5 prototype versions have been built, and Eurocircuits played a huge role in reducing the development cycle time, by providing excellent tools for making a first-time-right design, having a quick turnaround time, and even the capability to assemble prototypes.
Right now, the design can be found for free on GitHub, to serve as a reference design or to help other teams compete in the world solar challenge. To hopefully get more people interested in the design of high-efficiency power electronics.