Ethan's Projects

The Problem That Started It All

In my office, I have a pc that produced a ton of heat (9800x3d and a 5090), the issue is my apartment does not have individual room AC control so in order to keep the room temp manageable, I have a small fain I run in the windowsill. With home assistant, I had this setup to turn on after it reaches 73F in the room, the issue is though I had to way to detect if the window was closed or open. I had a couple options i could use a switch, but that would not detect when its partially open, as i only open the window just enough for the fan. So i needed something that would measure the distance rather than a binary open/closed sensor.

Initial Research & Exploration

For this application, I need precise distance measurement rather than simple binary detection. While my primary use case is window position monitoring, this sensor design can work for many distance sensing applications.

Commercial Options:

Traditional binary sensors (door/window, motion) only provide on/off status
Purpose-built distance sensors are expensive and often lack smart home integration

DIY Approach:

Time-of-Flight sensors provide precise distance measurement with excellent accuracy
VL53L1X offers extended range (up to 4m) suitable for various monitoring applications
ESPHome provides seamless Home Assistant integration without custom firmware development

The design uses a VL53L1X Time-of-Flight sensor for precise distance measurement. While optimized for window monitoring, the same hardware can be used for garage parking assistance, liquid level monitoring, occupancy detection, or any application requiring accurate distance sensing.

Design Requirements & Constraints

Design Requirements

Core Functionality:

Precise distance measurement for various monitoring applications
ESPHome integration for seamless Home Assistant connectivity
Dual power options: USB-C or 2x AA batteries in series (wires are ugly)
Compact form factor for versatile mounting in different locations

Power Management:

Automatic switching between USB-C and battery power
Long battery life when running on AA batteries
Low power sleep modes when not actively measuring

Integration:

ESPHome configuration for easy Home Assistant discovery
Configurable measurement reporting and automation triggers
OTA updates through ESPHome dashboard

Versatility:

Applicable to window monitoring, parking assistance, liquid levels, occupancy detection
Adjustable measurement intervals and thresholds via ESPHome configuration
Multiple mounting orientations and installation options

Component Selection

VL53L1X Time-of-Flight Sensor:

Extended range up to 4 meters - suitable for various distance sensing applications
High accuracy (±3%) for precise measurement in different scenarios
Narrow beam angle reduces interference from nearby objects
Low power consumption ideal for battery-powered operation
I2C interface simplifies integration and wiring

ESP32-S3 Microcontroller:

Proven WiFi reliability for Home Assistant connectivity
Dual-core architecture for handling sensor and networking tasks simultaneously
Multiple GPIO options for flexible power management and expansion
Excellent ESPHome compatibility with extensive sensor library support
Built-in USB connectivity for easy programming and debugging

Dual Power System Design

Power Source Options:

USB-C: For permanent installations where power is available
2x AA Batteries: For flexible placement where USB power isn’t practical
Automatic Switching: Circuit detects USB-C presence and switches power source

Power Management Considerations:

Voltage regulation from 3V (2x AA) and 5V (USB-C) to 3.3V system voltage
Battery monitoring for low power alerts
Deep sleep modes to maximize battery life when on AA power
Power path switching to seamlessly transition between sources

ESPHome Integration

Configuration Approach:

ESPHome YAML configuration for VL53L1X sensor
Automatic Home Assistant device discovery
Position reporting as distance sensor entity
Battery level monitoring when on AA power

Key Features:

Distance measurement updates at configurable intervals
Deep sleep between measurements for battery conservation
OTA updates through ESPHome dashboard
Diagnostic sensors for WiFi signal strength and battery voltage

Applications and Use Cases

Primary Use Case (Window Monitoring):

Mount sensor on window frame to measure distance to sliding window panel
Determine exact window position for automated fan control
Provides precise position data vs binary open/closed detection
Enables automation based on window opening percentage

Alternative Applications:

Garage Parking: Mount to measure car position for parking assistance
Liquid Level Monitoring: Non-contact measurement of tank levels
Occupancy Detection: Detect presence in doorways or specific areas
Security Monitoring: Alert when objects move into restricted zones

Mounting Flexibility:

Small form factor for discreet installation in various locations
Sensor beam alignment configurable for different mounting orientations
Power option flexibility (USB-C where available, batteries elsewhere)
Weather-resistant design for indoor or covered outdoor installations

Design Challenges

Dual Power Management:

Seamless switching between USB-C and battery power
Voltage regulation from different input voltages (3V AA vs 5V USB-C)
Battery monitoring and low power alerts
Optimizing sleep modes for battery longevity

Sensor Integration:

VL53L1X requires 2.8V logic levels with 3.3V ESP32-S3
I2C communication reliability over varying distances
Calibration for different window materials and colors
Temperature compensation for outdoor installations

Form Factor Constraints:

Compact PCB design to fit window frame aesthetics
Component placement for optimal antenna performance
Enclosure design for weather protection
Mounting hardware for various window frame types

Project Status

This project is currently in the design phase. The goal is to create a versatile distance sensing solution that can be deployed for various monitoring applications with flexible power options.

Current Progress:

Component selection completed (ESP32-S3 + VL53L1X)
Power management approach defined (USB-C + AA battery dual power)
ESPHome integration strategy planned
Form factor requirements established for versatile mounting

Next Steps:

Schematic design and PCB layout
Enclosure design for various installation environments
ESPHome configuration development with configurable thresholds
Prototyping and testing across different use cases

ESPHome Configuration Approach

Sensor Configuration: The VL53L1X will be configured in ESPHome using the appropriate sensor platform, providing distance measurements at regular intervals with configurable update rates.

Power Management: ESPHome’s deep sleep functionality will be utilized to maximize battery life when running on AA batteries, with wake intervals optimized for the window monitoring use case.

Home Assistant Integration: ESPHome automatically handles Home Assistant discovery, creating entities for window position, battery level, and device diagnostics without manual MQTT configuration.

Home Assistant Integration

ESPHome will automatically create entities in Home Assistant for:

Core Entities:

sensor.distance_measurement - Distance reading in centimeters
sensor.distance_battery - Battery percentage (when on AA power)
binary_sensor.threshold_triggered - Configurable distance threshold status
sensor.distance_signal_strength - WiFi signal strength for diagnostics

Automation Examples:

Window Monitoring: Turn on/off fans based on window position
Parking Assistance: Alert when car reaches optimal parking position
Security: Notify when objects enter monitored zones
Level Monitoring: Track liquid levels in tanks or containers
Occupancy Detection: Detect presence in specific areas

Design Goals

This general-purpose distance sensor aims to provide: