Angel Sanchez Llamas
← All projects
Completed · in daily use

Vehicle Reverse Sensor

A custom ultrasonic proximity sensor I designed and installed in my own car. I validated an outlier-rejection algorithm through experiments, and the system has run reliably for more than two years.

Type
Personal project
Focus
Circuit design, signal filtering
Date
Feb 2024
Photo: sensor installed on vehicle
−65%
Erroneous distance readings after outlier rejection
2+ yrs
Of real-world daily operation
3.3 V
Steady supply from a buck converter

The problem

My car had no reverse sensor. Cheap ultrasonic sensors produce noisy readings, and in a car, false alarms quickly make a sensor useless.

Design decisions

Buck converter for a stable 3.3 V supply

Question
How do I power 3.3 V electronics from a car's electrical system, which varies?
Method
Integrated a buck converter into the custom circuit.
Outcome
A steady 3.3 V supply, and the system has stayed working for 2+ years.

Outlier rejection on distance readings

Question
How do I stop spurious readings from triggering false alerts?
Method
Developed an outlier-rejection algorithm and tested it experimentally by comparing readings before and after.
Outcome
65% fewer erroneous distance readings.

Build

Photo: circuit / schematic
Sensor circuit with buck converter.
Plot: raw vs filtered readings
Raw and filtered distance readings.