Sensy-One S1 Pro Multi Sense mmWave Multisensor | LD2450

Multifunctional Presence and Air Quality Sensor for Home Assistant

The Sensy-One S1 Pro Multi Sense is an open-source presence and environmental sensor specifically designed for Home Assistant. This compact sensor combines advanced mmWave presence detection via the Hi-Link LD2450 radar module with comprehensive air quality monitoring, ambient light and UV sensing, an RGB status light, and a built-in buzzer for alerts. The device runs on ESPHome firmware and integrates automatically with Home Assistant via BLE Improv (automatic Bluetooth pairing) or a wireless access point when Bluetooth is unavailable.

Connectivity and Protocols

The S1 Pro uses Wi-Fi and Bluetooth Low Energy (BLE) thanks to the ESP32-C3-MINI-1-N4 module. The sensor communicates via ESPHome and works seamlessly with Home Assistant without additional hubs or dongles. Thanks to automatic Bluetooth pairing, the device is instantly recognized by HA, so you don't need a separate configuration app. The sensor sends presence, position, and motion updates every 30 milliseconds, ensuring real-time responsiveness in your automations.

Platform compatibility

Fully optimized for Home Assistant via ESPHome, the S1 Pro is primarily intended for HA users and features its own Zone Editor integration with heatmap functionality . Its open-source firmware allows you to customize the sensor to your needs, including adding additional add-ons, adjusting zones, and setting triggers for scenes and automations.

Nutrition and Energy

The sensor operates on 5V USB-C and has a standard USB-C port on the bottom for mounting. Optionally, you can use the S1 Pro Female USB-C Add-on to position the sensor upright, or the S1 Pro Male USB-C Add-on to connect directly to a wall adapter without a cable. Power consumption is low thanks to the ESP32-C3.

mmWave Presence Detection

The Hi-Link LD2450 radar module offers 24 GHz mmWave detection with a range of up to 6 meters, a 120° horizontal field of view, and a 70° vertical range. The sensor detects up to three people simultaneously and reports their position, speed, and movement in real time. You can set up to 3 detection zones (expandable to 10 in a future update) and 1 exclusion zone to ignore movement from fans or 3D printers. Each zone has adjustable presence delay and motion thresholds, and reports the number of targets, occupancy, and motion activity per zone.

Air quality with Bosch BME688

The built-in Bosch BME688 sensor is the world’s first gas sensor with artificial intelligence and measures estimated CO₂ levels, gas resistance, Air Quality Index (IAQ, a measurement value between 0 and 500), estimated VOC (volatile organic compounds) levels, humidity, temperature, and air pressure. The BME688 detects VOCs (volatile organic compounds), sulfur compounds (an indicator of bacterial growth), and other gases such as carbon monoxide and hydrogen in extremely low concentrations. The sensor uses a heated element that reacts to chemically reactive gases and creates a unique fingerprint by measuring at different temperatures. The S1 Pro incorporates Bosch features such as the accelerated 4-day calibration, which ensures air quality measurements become more accurate more quickly after a move. The BME688 offers ±3% accuracy for humidity, ±0.5°C for temperature (0-65°C), and ±0.6 hPa for air pressure (300-1100 hPa).

Optional CO₂ sensor ( SCD40 Add-on )

For high-quality CO₂ measurements, the S1 Pro supports an optional ** S1 Pro CO₂ Add-on ** with Sensirion SCD40 module, which can be connected to the front via a plug-and-play connector without soldering. The SCD40 measures CO₂ with professional measurement technology and offers an accuracy of ±50-100 ppm between 400 and 2000 ppm. The module also reports temperature and humidity. The SCD40 utilizes altitude compensation via the BME688 pressure values, which improves CO₂ accuracy at different altitudes and weather conditions. Unlike the BME688, which estimates CO₂ via VOC measurements, the SCD40 provides true CO₂ concentrations for accurate air quality monitoring.

Automatic Sensor Compensation

The S1 Pro automatically compensates for sensor heating and housing influences through advanced humidity and temperature correction. This ensures accurate measurements without manual calibration, even with temperature fluctuations. Both sensors (BME688 and optional SCD40) always remain perfectly aligned.

Ambient light and UV sensing

The integrated Lite-On LTR-390UV sensor measures both illuminance (lux) and UV index (UVI). This enables smart lighting control based on natural light and provides insight into sun exposure. The sensor responds quickly and accurately, which is useful for adaptive lighting that tracks daylight levels or for automatically closing blinds in high UV conditions.

Visual and Auditory Feedback

On the back of the board is a WS2812B RGB LED that projects light onto the wall. This allows you to provide visual feedback for presence, alerts, or mood lighting via Home Assistant automations. The sensor also has a built-in Huaneng MLT-8530 buzzer that produces 80–90 dB of sound at 2.7 kHz, ideal for notifications, alerts, or presence confirmations. Both functionalities are fully configurable within ESPHome and Home Assistant.

Physical and Installation

The enclosure is custom-designed to minimize interference with mmWave signals and maximize airflow for accurate sensor measurements and cooling. High-quality enclosure with a sleek, professionally finished surface.
Dimensions: 50 mm high, 35 mm wide, 25 mm deep.
The sensor has a standard USB-C port on the bottom, a plug-and-play connector on the front for the CO₂ module (SCD40 add-on), and a plug-and-play connector on the back for USB-C add-ons (Male/Female modules).

Mounting options (Add-ons)

The S1 Pro supports several optional mounting adapters for flexible placement. The S1 Pro Corner Ball Mount Add-on allows you to precisely position the sensor at 90-degree angles, while the S1 Pro Standard Ball Mount Add-on allows for tight mounting on any wall surface. Both ball mounts offer full pan and tilt capabilities for perfect sensor alignment. For portrait mounting, use the S1 Pro Female USB-C Add-on to position the sensor upright when the bottom is not accessible. The S1 Pro Male USB-C Add-on allows direct connection to a wall adapter without a cable. For precise CO₂ measurements, the S1 Pro CO₂ Add-on is available with the Sensirion SCD40 module, which simply connects via the Mezzanine connector on the front.

Software and Updates

The S1 Pro runs on ESPHome firmware , which is fully open-source and accessible via GitHub. Updates are delivered wirelessly via Home Assistant or ESPHome, without requiring physical access to the sensor. The community and manufacturer offer active support via Discord, GitHub, and YouTube, including a web-based Zone Editor for easy configuration of detection zones without programming knowledge. The firmware is regularly updated with new features and accuracy improvements. All firmware releases are documented on GitHub with detailed changelogs and installation instructions.

Environment and Sustainability

Intended for indoor use in standard living and working spaces. The BME688 operates electrically between -40°C and +85°C, with full accuracy between 0°C and 65°C at 10-90% relative humidity. The SCD40 (optional) operates optimally at room temperature and normal humidity. The enclosure is designed for maximum airflow to maintain sensor accuracy and extend component life. Not suitable for humid or dusty environments such as bathrooms or workshops without additional protection. The resin enclosure is durable and heat-resistant. The BME688 complies with European safety standards.

Performance and Responsiveness

The mmWave sensor sends updates every 30 milliseconds , ensuring highly responsive presence detection. The BME688 reports at intervals configurable in ESPHome, typically every few seconds to minutes depending on your preference. The BME688 has a response time of approximately 8 seconds for humidity changes and less than 1 second for gas detection in continuous mode. The SCD40 (optional) measures CO₂ levels every 5 seconds by default, but this can be adjusted. The LTR-390UV responds quickly to light changes for real-time lighting control. The Wi-Fi connection via the ESP32-C3 provides low latency and stable communication with Home Assistant, even with frequent updates from multiple sensors simultaneously. The accelerated 4-day calibration allows for faster adaptation to new environmental conditions.

Air Quality Index (IAQ) Classification

The BME688 with Bosch software provides an Air Quality Index (IAQ) ranging from 0 (clean air) to 500 (heavily polluted), with a resolution of 1. The index automatically adjusts to typical environments and reports air quality in 7 categories: Excellent (0-50), Good (51-100), Lightly polluted (101-150), Moderately polluted (151-200), Heavily polluted (201-250), Severely polluted (251-350), and Extremely polluted (>351). The sensor detects VOCs from paint, new furniture, garbage, cooking odors, exhaled breath, sweat, and other VOC sources . The BME688 detects sulfur compounds with 95% accuracy, indicating bacterial growth or decayed organic materials. The sensor has an internal deviation of ±15% IAQ after calibration and a long-term stability of ±1% IAQ drift per year under normal indoor air conditions.

Security and Privacy

The sensor operates entirely locally, without a cloud connection, guaranteeing your privacy and security. Firmware updates are optional and entirely under your control.

Package Contents

You get the S1 Pro Multi Sense sensor as standard with built-in mmWave, BME688, LTR-390UV, RGB LED, and buzzer. The sensor has a USB-C port on the bottom and two plug-and-play connectors for add-ons. Five add-ons are sold separately: **S1 Pro CO₂ Add-on** (SCD40 module), **S1 Pro Female USB-C Add-on**, **S1 Pro Male USB-C Add-on**, **S1 Pro Standard Ball Mount Add-on**, and **S1 Pro Corner Ball Mount Add-on**. A USB-C power cable is not included; you will need a standard USB-C cable and 5V adapter.

Usage scenarios

The S1 Pro is ideal for Home Assistant users who want to combine reliable presence detection and air quality monitoring in one compact device. Thanks to mmWave technology, the sensor detects presence even when you are sitting still, unlike PIR sensors. Perfect for automatically switching lights on and off, ventilation based on CO₂ levels or air quality index, and adaptive lighting based on daylight. The BME688 warns of elevated VOC levels from cooking, cleaning products, off-gassing from new furniture, or overcrowding. The optional SCD40 module offers accurate CO₂ measurements with altitude compensation for healthy indoor air, ideal for bedrooms, offices, and classrooms. The modular add-ons allow for flexible placement, from corner to vertical mounting.

Plus points

• Seamless integration with Home Assistant via ESPHome and automatic Bluetooth pairing
• Advanced mmWave detection (LD2450) with multi-target tracking, positioning and configurable zones
• Bosch BME688 AI gas sensor with air quality index, VOC and sulfur compound detection
• Bosch software with accelerated 4-day calibration and automatic compensation for accurate measurements
• Optional high-quality CO₂ sensor (SCD40) with altitude compensation for accurate measurements
• Five modular add-ons for flexible mounting and accurate CO₂ measurements without soldering
• Fully open source with active development, regular firmware updates and extensive documentation
• Web-based Zone Editor for easy configuration without programming knowledge

Negative points

• Limited platform support outside of Home Assistant; no native integration with Google Home, Alexa, or Apple HomeKit

Manual and support

• You can find the manual here
• Need support? The Sensy-One team is active on Discord and happy to help!

Frequently Asked Questions

Does the S1 Pro Multi Sense work with Home Assistant?

Yes, the S1 Pro is specifically designed for Home Assistant and integrates automatically via Bluetooth pairing or a wireless access point. The sensor runs on ESPHome firmware and is instantly recognized by the HA without any additional configuration.

How do I connect and install the S1 Pro?

Connect the sensor to a 5V USB-C power supply via the port on the bottom. Upon initial use, the sensor creates a wireless access point or uses automatic Bluetooth pairing to connect to your Wi-Fi and Home Assistant. Follow the instructions in the HA app or connect via 192.168.4.1 in your browser. Mounting is possible via the standard USB-C port, or with optional ball mounts and USB-C add-ons. For zone configuration, use the web-based Zone Editor, no programming required. There's now also a custom integration that makes setting up your zones even easier: the Sensy-One Zone Editor with Heatmap functionality.
TIP: Also check out the S1 Pro Github page for new updates and manuals

What network protocol does the S1 Pro use?

The sensor uses Wi-Fi (2.4 GHz) and Bluetooth Low Energy (BLE) via the ESP32-C3 module. Communication with Home Assistant occurs via ESPHome over Wi-Fi, and BLE is used for automatic pairing.

Does the S1 Pro support Matter?

No, the S1 Pro does not support Matter. The sensor is fully focused on Home Assistant via ESPHome and does not offer native Matter support.

What is the range of the mmWave sensor?

The Hi-Link LD2450 radar module has a range of up to 6 meters , a horizontal field of view of 120°, and a vertical range of 70°. The sensor detects up to three people simultaneously and reports position, speed, and movement every 30 milliseconds.

What is the difference between the BME688 and the optional SCD40 CO₂ sensor?

The BME688 estimates CO₂ levels by converting VOC (volatile compounds) measurements using Bosch software. This is suitable for general air quality monitoring. The SCD40 (optional add-on) measures real CO₂ concentrations with professional technology and offers an accuracy of ±50-100 ppm, ideal for accurately monitoring CO₂ levels in bedrooms, offices, and classrooms. The SCD40 uses altitude compensation via the BME688 for accurate measurements at various altitudes and weather conditions.

What add-ons are available for the S1 Pro?

Five add-ons are available: the S1 Pro CO₂ Add-on with the Sensirion SCD40 module for precise CO₂ measurements with height compensation, the S1 Pro Female USB-C Add-on for portrait mounting, the S1 Pro Male USB-C Add-on for direct connection to a wall adapter, the S1 Pro Standard Ball Mount Add-on for mounting on any wall surface, and the S1 Pro Corner Ball Mount Add-on for positioning at 90-degree angles. All add-ons connect via plug-and-play connectors without soldering.

How do I update the firmware on the S1 Pro?

Updates are handled wirelessly via Home Assistant or ESPHome. Download the desired firmware version from the GitHub releases page and follow the instructions in the repository. After an update, it may take a few days (approximately 4 days) for the BME688 air quality measurements to recalibrate. For a factory reset, you can use the official ESPHome Web Wizard via USB-C connection to your computer.