Introduction: Brake Light - Formula SAE Car
Formula SAE is a competition for engineering students all around the world, organized by SAE International, that provides the opportunity to students to apply the theoretical knowledge they acquire on the classroom by designing and building an open-wheel prototype. Our team is one of the best teams in Brazil, recently achieving 3rd place overall on the nacional step of Formula SAE, Formula SAE BRASIL.
On this competition all teams must conform to a very strict set of rules, which states that all vehicles, in order do take part in the dynamic events, must have a part that, although simple, is crucial for the teams participation and requires attention in its design and construction, a Brake Light.
This brake light must be operational throughout all of the dynamic events, when the car is on track, under penalty of the team being disqualified from the event, and thus is extremely important that this part, specifically the Printed Circuit Board, PCB, be of high quality, and from this demand arose the necessity of a sponsorship like from JLCPCB, one of the biggest manufacturer of this boards. JLCPCB (Shenzhen JLC 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. Visit their website: jlcpcb.com
Step 1: CAD Design
The part was projected using CAD, and its design is based on the competition rules, which state that it must be rectangular, triangular or near round shape, with a minimum shining surface of 15 cm². The full assembly consist of a base, body, a lid that fits the LEDs and fix them in place, as well as fixing points and supports for the PCB. The image below shows the complete assembly of the brake light.
Step 2: Electrical Diagram
The electronics require only LEDs and resistors, and is actuated by a sensor on the brake lines of the vehicle, that reads the pressure applied on the brakes and triggers the lights. The electronics are powered by the vehicles battery, which voltage ranges from 12V to 13V, and based on this parameters were selected resistors of at least 650Ω. The complete electrical schematic turns out like this:
Step 3: PCB Design
Based on the dimensions of the brake light case and the schematic, the PCB design is developed, and can be seen in the image below, with the dimensions in blue. The board traces have 30th (less then a mm) in width, which is enough to handle the current drained by the components. The components used are 0805 package resistors, and high brightness, 5mm LEDs.