Frequently Asked Questions (FAQ)

Product Variants

1. What is the difference between CeilSense Basic and CeilSense Complete?

The CeilSense comes in two variants:

CeilSense Basic includes:

• Hi-Link LD2412 mmWave radar (presence & motion detection)
• BH1750 ambient light sensor (LUX)
• Bosch BMP388 barometric pressure sensor
• 16× WS2812B RGB LED ring
• Wi-Fi, Ethernet & PoE support

CeilSense Complete includes everything from Basic, plus:

• Sensirion SCD41 sensor for CO₂, temperature & humidity measurements

Choose Basic if you primarily need presence detection and ambient lighting. Choose Complete if you want full environmental monitoring including air quality.

2. Can I upgrade from Basic to Complete?

Yes, upgrading is possible! Contact us via our contact page to purchase an upgrade kit. This kit includes:

• Sensirion SCD41 sensor module
• Special thermal isolation plate to maintain proper airflow and keep heat away from the sensor

Important: Simply buying an SCD41 sensor yourself and installing it will not work. The upgrade kit includes a specially designed plate that is required for accurate readings and proper thermal management. The sensor needs this plate to function correctly within the CeilSense housing.

Sensors & Detection

3. What sensors are included in the CeilSense?

CeilSense Basic:

• mmWave radar: Hi-Link LD2412 for presence and motion detection
• Ambient light (LUX): BH1750 (0-65,000 lux)
• Barometric pressure: Bosch BMP388 (300-1,100 hPa, ±0.08 hPa accuracy)
• LED Ring: 16× WS2812B individually addressable RGB LEDs

CeilSense Complete (all of the above, plus):

• Temperature: Sensirion SCD41 (-10°C to +60°C, ±1.5°C accuracy)
• Humidity: Sensirion SCD41 (0-100% RH, ±9% RH accuracy)
• CO₂: Sensirion SCD41 (400-5,000 ppm, ±50 ppm + 2.5% accuracy)

4. How does the mmWave radar sensor work?

The LD2412 emits millimeter-wave radar signals at 24GHz into the environment. When these signals hit a person or object, they bounce back. The sensor detects these returned signals and calculates motion, presence, and distance information. Unlike PIR sensors, mmWave can detect stationary people (like someone sitting, lying on a couch, or sleeping in bed).

5. What is the detection range of the mmWave radar?

The standard Hi-Link LD2412 sensor specifications:

• Maximum detection range: 9 meters (29.5 feet)
• Field of view: ±75° (150° total)
• Detection resolution: 0.2m, 0.5m, or 0.75m configurable
• Single-target tracking: Optimized for presence detection

The CeilSense is designed for ceiling mounting at 2-4 meters height, providing:

• Presence detection diameter: 2-6 meters
• Motion detection diameter: 8-12 meters

mmWave Sensor Options

6. What mmWave sensor modules are available for the CeilSense?

The CeilSense supports three Hi-Link mmWave radar modules:

Feature	LD2412 (Standard)	LD2450 (Optional)	LD6002B (Coming Soon)
Frequency	24 GHz	24 GHz	60 GHz
Max Range	9 meters	6 meters	TBD
Field of View	±75° (150°×150°)	±60°×±35° (120°×70°)	±60°
Target Tracking	Single	Multi (up to 3)	Multi with 3D
Position Tracking	No	Yes (X/Y zones)	Yes (3D)
Best For	Still presence detection	Multi-person tracking	Advanced 3D detection

7. What is the Hi-Link LD2412 sensor?

The LD2412 is the standard mmWave sensor included with every CeilSense. Key features:

• 24 GHz millimeter-wave radar
• 9 meter maximum detection range
• 150° × 150° field of view
• Single-target presence detection
• Configurable sensitivity for moving and still targets
• Perfect for: Detecting if someone is still in a room (sleeping, sitting, lying on couch)

This sensor excels at detecting stationary people, making it ideal for room occupancy detection and light automation.

8. What is the Hi-Link LD2450 sensor?

The LD2450 is an optional mmWave sensor you can install yourself. Key features:

• 24 GHz millimeter-wave radar
• 6 meter maximum detection range
• 120° × 70° field of view (azimuth × elevation)
• Multi-target tracking: Up to 3 people simultaneously
• Zone-based detection: X/Y coordinate tracking
• 0.75m resolution
• Perfect for: Tracking multiple people, zone-based automations

Choose the LD2450 if you need to:

• Detect and track multiple people in a room
• Create zone-based automations (e.g., different actions for different areas)
• Know the approximate position of people in a space

9. What is the Hi-Link LD6002B sensor?

The LD6002B is a next-generation 60 GHz radar module currently in development. Expected features:

• 60 GHz millimeter-wave radar (higher frequency = more precision)
• 3D human presence detection
• FMCW radar technology (Frequency Modulated Continuous Wave)
• Detects: Movement, micro-movement, and stationary humans
• Distance and speed calculation
• Perfect for: Advanced 3D detection and positioning

Software support for the LD6002B is being developed and will be available in a future firmware update. The sensor can be installed directly into existing CeilSense hardware.

10. Can I install a different mmWave sensor myself?

Yes! The CeilSense is designed to be modular. You can replace the standard LD2412 with an optional LD2450 sensor yourself. The LD6002B will also be installable once software support is released.

Note: When installing a different sensor, you'll need to flash the appropriate firmware variant for that sensor.

11. Can the CeilSense detect multiple people?

• LD2412 (standard): Single-target detection only. It detects presence but cannot distinguish between one or multiple people.
• LD2450 (optional): Yes! Can detect and track up to 3 people simultaneously with X/Y coordinate zones.
• LD6002B (coming soon): Yes, with 3D positioning capabilities.

12. Does the mmWave sensor detect through walls or ceilings?

Yes, mmWave radar at 24GHz can penetrate certain materials like thin drywall and wood. This means it might detect movement in adjacent rooms. You may need to adjust the sensitivity settings through:

• The device's web interface (access via IP address or hostname.local)
• Home Assistant device page
• HLK Radar Tool app

13. Will the sensor detect pets or other moving objects?

The mmWave sensor may detect larger pets or other moving objects like rotating ceiling fans. To minimize false detections:

• Position the sensor to focus on human activity areas
• Adjust the mmWave sensitivity settings
• Configure detection zones (with LD2450)
• Consider the field of view when mounting

CO₂, Temperature & Humidity (Complete Only)

14. How accurate is the CO₂ sensor?

The Sensirion SCD41 CO₂ sensor (CeilSense Complete only) has an accuracy of ±(50 ppm + 2.5% of reading). It measures CO₂ levels from 400 to 5,000 ppm, which covers typical indoor environments. This sensor is ideal for monitoring air quality and automating ventilation.

15. What can I do with CO₂ measurements?

You can create automations such as:

• Turn on ventilation or open windows when CO₂ levels exceed a threshold (e.g., 1000 ppm)
• Send notifications when air quality becomes unhealthy
• Control HVAC systems based on real-time air quality data
• Use the LED ring to display a visual warning when CO₂ is too high (e.g., red glow)

16. Why do my temperature readings seem inaccurate?

Every installation is unique! Several factors can affect temperature readings:

Installation variables:

• Ceiling material: Some ceilings retain more heat than others
• Insulation: Well-insulated ceilings may trap warm air around the sensor
• Airflow: Limited airflow in the ceiling cavity causes heat buildup
• Mounting depth: How deep the sensor sits affects air circulation

LED ring heat: The LED ring generates heat during operation, which can affect temperature, humidity, and CO₂ readings. To minimize this:

• Reduce LED brightness during continuous operation
• Use cooldown intervals between LED effects
• Avoid prolonged high-brightness LED animations

Calibration: Because every situation is different, you can calibrate the sensors to match your specific environment. Apply temperature offsets in ESPHome to correct for consistent differences between the CeilSense reading and a reference thermometer.

👉 See our Calibration Guide for detailed instructions on how to calibrate temperature, humidity, CO₂, and other sensors.

17. What is the barometric pressure sensor used for?

The Bosch BMP388 barometric pressure sensor (accuracy ±0.08 hPa) can be used for:

• Weather prediction and trend monitoring
• Altitude calculations
• Integration with weather stations
• Triggering automations based on atmospheric pressure changes

Light Sensor (LUX)

18. What can I do with the ambient light sensor?

The BH1750 light sensor measures ambient light from 0 to 65,000 lux. Common uses include:

• Automating lights based on natural daylight levels
• Adjusting smart blinds or curtains
• Creating "lights on at sunset" automations
• Monitoring light conditions in specific rooms

19. Does the light sensor work when mounted in the ceiling?

The light sensor works best when it has direct exposure to the ambient light you want to measure. Since the CeilSense is mounted flush in the ceiling, it measures the light reaching the ceiling level, which may differ from floor-level light. Keep this in mind when creating light-based automations.

LED Ring

20. What is the RGB LED ring used for?

The 16× WS2812B LED ring can be used for:

• Visual alerts (e.g., high CO₂ levels shown in red, presence detected)
• Status indicators (e.g., startup sequence with rainbow animation, connectivity status)
• Ambient lighting effects
• Custom notifications triggered by Home Assistant automations

21. Can I customize the LED ring colors and effects?

Yes! Through Home Assistant and ESPHome, you can fully control the LED ring:

• Set individual LED colors
• Create custom animations
• Trigger specific colors/effects based on sensor readings or automations
• Adjust brightness levels

Note: Extended LED operation generates heat that can affect sensor readings. Use cooldown intervals or reduce brightness during intensive use.

Power & Connectivity

22. What power options does the CeilSense support?

The CeilSense offers three power options:

• PoE (Power over Ethernet): 48V (802.3af compliant) — single cable for power and data
• Mains power: 110-240 VAC with internal EU-designed circuit and galvanic isolation
• USB-C: 5V ⎓ 1A

23. What is the power consumption?

• Standby: 1.2 W
• Active: up to 2.5 W

24. Can I use PoE for both power and network connection?

Yes! Using PoE (802.3af compliant) allows you to power the CeilSense and provide network connectivity through a single Ethernet cable. This is the cleanest installation option as you only need to run one cable to the ceiling.

25. Does the CeilSense support both Wi-Fi and Ethernet?

Yes, the CeilSense supports:

• Wi-Fi: IEEE 802.11 b/g/n (2.4 GHz), WPA/WPA2
• Ethernet: RJ45 10/100 Mbps with PoE support

The device ships with Wi-Fi firmware by default. If you want to use Ethernet/PoE, you need to flash the Ethernet firmware first via the quick-start page.

Installation

26. What ceiling cutout size is required?

The CeilSense requires a 68 mm diameter cutout, which fits standard Ø70 mm downlight cutouts. The total sensor height is 60 mm, with a flush depth of at least 48 mm required in the ceiling cavity.

27. At what height should I mount the CeilSense?

The recommended mounting height is 2-4 meters above the floor. This provides optimal detection coverage for both presence and motion sensing.

28. Can I use the CeilSense outdoors?

No, the CeilSense is rated IP20 and is designed for indoor use only. Exposure to high humidity, rain, or extreme temperatures could damage the device.

Home Assistant Integration

29. How do I connect the CeilSense to Home Assistant?

The CeilSense connects via ESPHome:

1. Power on the device
2. For Wi-Fi: Connect to the CeilSense hotspot (password: ceilsense) and configure your home network
3. For Ethernet: Connect via RJ45 (must have Ethernet firmware installed)
4. Home Assistant should automatically discover the device under Devices & Services
5. If not discovered, add the ESPHome integration manually using the device's IP address

30. How do I adjust the mmWave radar sensitivity?

Sensitivity adjustments can be made through:

• Home Assistant: Navigate to the CeilSense device page and adjust the sensitivity entities/sliders
• HLK Radar Tool app: Use the official Hi-Link app for fine-tuning (available for iOS and Android)

This allows you to reduce false positives or increase sensitivity for more precise detections.

👉 See our Calibration Guide for detailed instructions on adjusting mmWave sensitivity.

31. What automations can I create with the CeilSense?

You can create a wide variety of automations:

• Turn on lights when motion is detected
• Turn off lights when a room is unoccupied (after a delay)
• Adjust ventilation or HVAC based on CO₂ levels (Complete only)
• Control smart blinds based on light levels
• Send alerts for air quality issues
• Display LED ring alerts for various conditions
• Log and track environmental data over time
• Zone-based actions with LD2450 (e.g., lights on only in certain areas)

32. Is the CeilSense compatible with other smart home platforms?

Yes, it is compatible with any system that supports the ESPHome API. This includes Home Assistant and other platforms that can integrate with ESPHome devices.

33. Can I use multiple CeilSense devices in my home?

Yes! You can have multiple CeilSense devices connected to the same Home Assistant instance. Each device appears as a separate entity with many configurable options, allowing you to monitor and automate different rooms throughout your home.

Firmware & Updates

34. How do I update the CeilSense firmware?

There are two ways to update:

1. Via Home Assistant: Enable the Update entity (e.g., "CeilSense Firmware"), check for updates, and install. You can also enable auto-update.
2. Via ESPHome Dashboard: Click Install/Update on your device

Updates are delivered OTA (Over-The-Air), so you don't need physical access to the device.

35. Can I customize the CeilSense firmware?

Absolutely! The CeilSense runs ESPHome, which means you can:

• Adopt the device in ESPHome Dashboard
• Modify the YAML configuration
• Add custom sensors, automations, or integrations
• Deploy changes OTA

36. How do I switch between Wi-Fi and Ethernet firmware?

See our Network Configuration guide for detailed instructions on:

• Switching to Ethernet
• Switching back to Wi-Fi
• Ethernet requirements
• Firmware Type selector

Quick summary:

• WiFi → Ethernet: Connect Ethernet cable first, then use the Firmware Type selector in Home Assistant
• Ethernet → WiFi: Must flash via USB-C (selector won't work)

36b. What are the requirements for Ethernet/PoE?

• DHCP: Your network must provide IP addresses via DHCP
• Same VLAN: CeilSense must be on the same network/VLAN as Home Assistant
• No firewall blocking: Allow communication between CeilSense and Home Assistant
• PoE (optional): 802.3af compliant PoE switch or injector

See Network Configuration for full details.

37. How often does the CeilSense report sensor data?

The reporting frequency can be customized through the ESPHome YAML configuration. Default behavior:

• mmWave sensors: Report immediately on change (presence/motion state)
• Environmental sensors: Report every 60 seconds by default
• Light sensor: Report every 60 seconds or on significant change

You can adjust these intervals to balance responsiveness with network bandwidth.

Security & Privacy

38. Is the CeilSense secure?

Yes, the CeilSense communicates over your local network using encrypted traffic with the ESPHome API. This provides a secure, local connection without requiring cloud services. No sensor data is ever sent to external servers, ensuring your privacy.

39. Does the CeilSense require an internet connection?

For normal operation: No. The CeilSense works 100% locally. All sensor data stays on your local network between the CeilSense and Home Assistant.

The only external communication is for firmware update checks:

• The CeilSense periodically checks ESPHome/GitHub to see if a new firmware version is available
• This only checks the version number — no sensor data is transmitted
• You can disable this by adopting the device in ESPHome and removing the update component

Internet is NOT required for:

• Presence/motion detection
• Environmental sensor readings
• Home Assistant automations
• Any day-to-day functionality

What Makes CeilSense Special

40. What makes the CeilSense stand out from other presence sensors?

The CeilSense offers unique advantages:

• Elegant ceiling integration: Fits standard 68mm downlight cutouts for a clean, invisible installation
• Multiple power options: USB-C, 110-240V mains, or PoE — whatever suits your installation
• Modular mmWave: Choose from three different radar sensors (LD2412, LD2450, or upcoming LD6002B)
• Complete environmental monitoring: CO₂, temperature, humidity, pressure, and light (Complete variant)
• Visual feedback: 16 RGB LEDs for status indication and ambient effects
• Fully local: No cloud required, works with ESPHome and Home Assistant
• Dutch quality: Designed and developed in the Netherlands

Warranty & Support

41. What is the warranty for the CeilSense?

Please refer to our Warranty and Support page for detailed warranty information. If you experience any issues, our support team is available to assist with troubleshooting or replacement.

42. Where can I get help if I have problems?

• Check the Troubleshooting guide
• Visit our support page at smarthomeshop.io
• Contact us via email or our website
• Join our Discord community for peer support