Work03EVolocity
Connected systems for an electric vehicle.
01 · Context
EVolocity is a New Zealand programme where students design, build and race their own electric vehicles. We built two.
The first was car 66, the 2023 race kart. My part was the monitoring system: sensors, an ESP32, the displays and the telemetry going over Wi-Fi and cellular. I also drove it.
The second was the four-wheeled kart we built in 2024. That one I built the entire system for: the central ECU, the sensors, the control box, the battery testing and the steering wheel with the displays set into it.
02 · Architecture
The data path, block by block. Hover or tap a block to see its job.
Inspector
VehicleThe electric vehicle itself. Every signal starts here.
MQTT topics, car 66 · published every 2 s
03 · Decisions
On paper: Wi-Fi on the chip, low cost and plenty of I/O.
MineIt’s easy to program and dumb enough to just do the job, so I never had to worry about firmware. It’s cheap, so a broken one gets swapped, not repaired. And it has analog inputs, which the Pi doesn’t.
On paper: lightweight publish/subscribe messaging made for small devices and flaky links.
On paper: a full Linux computer that can collect messages and run dashboard software.
On paper: visual flows for wiring live data into a dashboard quickly.
On paper: a programmable brushless motor controller with an RS232 port.
MineThe cheap controllers had no features. The Kelly is programmable from a laptop over RS232, so I could set continuous and peak power (we had a 2 kW limit, 3 kW peak), the low-battery cutoff and the regen current. Regenerative braking puts energy back into the battery instead of into heat, and it works at low speed, so the disc brakes only have to do the emergency stop.
On paper: heavier than aluminium, easier to build with school tools.
MineThe plan was metal. Then Tait Electronics funded us on the condition that the kart was eco-friendly, so the frame became wood, drawn up in Fusion 360. Phase one was a basic car that drives with no microcontrollers at all: a 2 kW Kunray motor, the controller, a battery, brakes and a throttle. The control system came after.
04 · Build
Car 66, 2023: the monitoring system went onto the team’s race kart. An ESP32 reading the vehicle, pushing volts, speed and current to four small displays and over MQTT to the Pi.
The four-wheeled kart, 2024: this time the whole electrical system was mine. Chassis drawings, a central ECU, a motor controller and control box, a battery pack tested on bench supplies, and a steering wheel we printed with two displays set into it, so the readings live in the driver’s hands.
I planned it in three phases with my mentor, Thomas. One: a basic car that drives, no microcontrollers. Two: the control system, with voltage, current and temperature monitoring, a dashboard, crash detection and thermal shutdown. Three: autonomy, which was never funded. Everything got tested on a rig before it went near the kart.
Requirements I set for the 2024 system
2023 · Car 66 · the monitoring system
2024 · Four-wheel kart · the whole system
05 · What broke
The Raspberry Pi failed to get onto the internet in the middle of a demo. The vehicle was fine and the ESP32 kept reading and publishing, but the data path stopped at the Pi, in front of people.
The cheap, dumb part of the system did its job. The part that depended on a network connection was the part that failed when it mattered.
06 · Result
EVolocity Canterbury Regional Finals, 2023. Team Trevor, Hagley College.
07 · Today
A touchscreen dashboard in the vehicle: every reading on one screen, with a speedometer. The driver sees the numbers whether or not the link is up, and the network becomes a bonus instead of a dependency.