Connecting a race car to the race team

Let’s start from the basics: what is formula student

We are talking about a type of formula racing but with two catches: first of all as can be deduced from the name the teams are made of university students (mainly future Engineers) and secondly we aren’t talking just about a conventional race as every team competes in building not just a small single seater race car but rather a proof of concept product aimed to attract funding for the commercial production.

The target demographic is the “week-end racing enthusiast”, there are some safety requirements and a few limitations, as for the rest it’s up to the team to design and build the prototype, you obviously can’t build the vehicle of hard to source or expensive parts as it needs to be viable and most importantly fit the limited resources available acquired from a handful of sponsors

UniPg Racing Team

The university of Perugia, a city located right in the centre of Italy, founded its racing team in 2011 and mostly competed in the Italian Formula ATA yearly competition hosted at Varano Melegari circuit that attracts teams from all over continental Europe. The team also participated in some events outside of its home turf such as Formula Student Spain. Covid took a hard hit on hand-on group activities, including formula student but during the 2023/24 season UniPg racing bounced back with more than 70 students actively working on the project and reestablishing ties with sponsoring companies.

We were and still are (for the moment) quite under-funded relative to other teams but in this race, money isn’t a requirement as spending is a grading metric where bang-for-buck wins. You need a viable product that stands out, not a fancy paperweight

Telemetry

Telemetry is an important aspect of our project that we wanted to add as an inexpensive feature to market.

With this term we refer to a system composed of 5 PCBs connected to various sensors that allow the pilot to use the vehicle efficiently and allow the team in the box to monitor the health of crucial systems remotely.

Following the rugged KISS design principle, we opted to base all the elements on the Nucleo STM32F446RE boards that allowed for quick development of “shields” specific for any application.

As you can see, we still need to develop and manufacture PCBs, we could’ve gone with DIY chemical etching or cnc routing but that won’t cut it for a commercial product (pun not intended) as we are talking about time consuming (therefore expensive) and dangerous (if not taken seriously and therefore once again expensive) jobs. By offloading the manufacturing, we can save a lot of money overall and even with time running out with JLCPCB we can get the boards delivered by the end of the week, that’s quicker than the components will take to ship! Prototyping with quality PCBs that have a silkscreen and a solder mask becomes a no-brainer as that’s less time wasted looking at a schematic or removing solder blobs.

There is also the issue that generally shields can be made with single layer boards with a couple of assembly tricks and a few jumper bridges. As our boards are at the limit of complexity for such a design, we could make the boards ourselves but when making use of commercial manufacturers such as JLCPCB a two-layer PCB is considered a basic design with no added cost over a single layer board.

Special Thanks to JLCPCB who made our ideas possible, not only by sponsoring us but by providing an essential service for our project’s development quickly and cheaply where other competitors failed.

Some details on the board and interesting design choices

While we can’t provide Gerbers as we are in a competition after all we can talk about some design choices we have implemented. (fun fact you can still request a quote on JLCPCB without having to upload anything or even create an account)

For example, we opted to use THT holes as makeshift vias since boards were still being designed while we were searching for a sponsor. For this reason, while designing on mostly on a single layer we routed traces on the opposite copper face where we expected jumpers, this way there was no need to adapt out design for two layer and you could to if you’re not sure you can make the pcb yourself.

Keep in mind that if you take full advantage of the two layers and their copper pours from the start you can greatly simplify the routing, therefore this design choice shouldn’t be taken lightly.

As for the content of the boards themselves we have 5 different PCBs that each fit in a 60x70mm, having them professionally made allows us to include mounting holes and rounded edges effortless, which in a vibrating environment such as automotive is a must. They all share the same shape that is mostly based on the nucleo board mounted underneath with some clearance for access to the buttons mounted on said board. We can provide an early revision of that nucleo footprint for the good of all makers

All boards share a CAN bus transceiver circuit as the nucleo boards support the protocol but lack the line driving capabilities. Here we went with the choice of implementing both a baked in circuit and an easily swappable module mount for flexibility and redundancy.

All boards also share a reverse polarity protection and overcurrent protection with only UartToCan, the board that handles translation and power for the raspberry pi controlling the dash having a crowbar circuit just in case something happens to the 5v rail making it not 5v anymore and destroying an expensive and important component. We also went with a solderless selector for the regulator selection as the boards are powered by 5v but not bypassing the intermediate 5v LDO already present in the nucleo while costing some voltage allows the boards to withstand the full battery voltage should the regulator fail.

A developing story

To find out more about our team’s progress and check out the actual PCBs ordered from JLCPCB you can follow unipgracing_team on insagram.

On our website other social media links can be found