Drexel Electric Racing Formula SAE EV

Drexel Electric Racing

Drexel Electric Racing is Drexel’ University’s all electric, open wheel, formula style racecar team. We design, build, and race a car in a yearly FSAE competition against other universities.

2022 Redesign

In 2022, Drexel Electric Racing is going to be attending its first FSAE competition. We will be going to Michigan to compete against other teams and present our designs to judges from the automotive industry. 

GLV Breakout

The Ground Low Voltage system is designed to provide power to all the low voltage systems in the car. This board takes 24v from a sealed lead acid (SLA) battery and splits it into 24v fused, 12v, and 5v connections. The 12v and 5v connections are managed by a DC-DC buck converter supplied by Vicor. These DC-DC converters have high efficiency and reliability.



Accumulator and Temperature Monitor

Our battery system features a temperature sensing circuit, but unfortunately the built-in temperature sensors on our battery modules are not compatible with our BMS. For this reason, we built the Temperature Monitor circuit which uses three analog multiplexers to read temperature signals from the 8 segments in each of 6 segments. The data is then collected and read in a Teensy microcontroller with a high-resolution DAC. Data is then sent via CAN to the battery management system.

Shutdown

Our shutdown board takes signals from all safety-critical systems and these signals keep relays open to allow for a 12-volt voltage to pass through the circuit. If one of these signals has an issue, the relay will close, stopping the voltage from running through the circuit and shutting down the car. This circuit keeps the driver safe in case of a system failure. This circuit also has the precharge relay for our car which allows for the car to be turned on by supplying the relays with enough voltage to switch them from their initial normally open state to closed.




Dashboard

The Dashboard circuit is a raspberry pi powered screen and can receive CAN signals from a bunch of different systems in the car. It presents to the driver information about the state of charge of the batteries, temperature, and various other programmable functions. The dashboard can take inputs from buttons that are on the steering wheel, which is connected through a quick-disconnect connector.

Tractive System Active Light (TSAL)

Whenever the car is on, there must be an indicating light at the top of the roll hoop to show that high voltage is present in the tractive system. This is achieved using an optocoupler to maintain isolation between the high voltage and low voltage segments of the car. Then, 24v is used to activate red or green LEDs on the top of the car to indicate exactly what state the car is in.


Pedal Box

The pedal box is comprised of the APPS and the BSE. The APPS is composed of two different linear potentiometers mounted on the acceleration pedal. This is to be done in such a way that the potentiometers have different transfer functions which can be compared and checked against each other. If the APPS finds that the potentiometers disagree on the pedal position by more than 5%, power to the motor is shut down. The BSE is comprised of two different pressure sensors in the front and rear brake master cylinders, and serves much the same function.

BSPD

The BSPD is a digital logic circuit that takes inputs from the pedal box sensors. This is a crucial piece of safety equipment in the case something is significantly wrong with the control system of the car. If the motor is powered, and the brakes are pressed for a significant amount of time this circuit will engage a shutdown. In the case of a “runaway accelerator” or stuck pedal, you’ll be glad this circuit is there to turn off the car after you stomp on the brakes.


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Apr 28,2022
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