Standard model rocket flight controllers are functional, but designing and building your own from scratch is a highly rewarding way to learn embedded systems, circuit design, and telemetry logging.
The Architecture
For the Phoenix-1 avionics bay, I selected the ESP32-S3 microcontroller. It provides high processing speeds, dual cores, built-in flash, and built-in Wi-Fi and Bluetooth which are invaluable for ground testing and wireless data retrieval.
The sensor package consists of:
- BMP390 barometric pressure sensor (for altitude tracking and apogee detection).
- BMI270 6-axis IMU (for accelerometer and gyroscope readings to measure flight tilt and rotational stability).
- MicroSD Card Slot connected via SPI for raw data logging at 100Hz.
Power Delivery & Pyro Channels
Operating in a high-vibration environment requires stable power. I designed a dual-stage regulator system to step down a 2S LiPo battery (7.4V) to 3.3V for logic, isolating the microcontroller from transient noise. The pyro channels for deploying the drogue and main parachutes are triggered using logic-level N-channel MOSFETs (IRL3705N), protected with optocouplers to prevent any noise from the high-current black powder matches from resetting the processor.
Lessons Learned
During our first ground test, we realized that the high vibration during motor ignition could momentarily shake the MicroSD card loose in standard push-push holders, causing logging failure. For future revisions, we are moving to an onboard SPI NAND flash chip soldered directly to the board, which offers absolute shock resistance.