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Detect stationary humans with the HLK-LD2420 24GHz Radar. Superior to PIR, this mmWave sensor detects micro-motions like breathing. Configurable via Serial/App. Ideal for smart home automation.
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Quality Advantage: The "True-Presence" Upgrade Cheap doppler radar modules often suffer from "ghost triggers" caused by fans or curtains. The HLK-LD2420 uses advanced 24GHz millimetre-wave technology with a highly optimised antenna array to distinguish between a human and random noise. It allows you to configure sensitivity zones and duration thresholds via a mobile app, giving you industrial-grade control in a DIY package. Probots™ Lab Verified, we have tested this module to confirm it reliably detects breathing at up to 2-3 meters and gross movement up to 8 meters, making it the gold standard for modern smart homes.
Key Applications & Projects
True Smart Lighting: Lights that stay on as long as you are in the room, regardless of how still you are sitting.
Security Systems: Hidden detection. Since radar passes through plastic and wood, you can hide this sensor inside a wall or furniture for invisible security monitoring.
Elderly Monitoring: Detect if a person has been in the bathroom for an unusually long time without privacy-invasive cameras.
Bed Occupancy: A non-contact way to trigger "Sleep Mode" automations when you get into bed.
Specifications
Model: Hi-Link HLK-LD2420.
Frequency: 24 GHz (ISM Band).
Modulation: FMCW (Frequency Modulated Continuous Wave).
Detection Type: Human Presence (Motion + Micro-motion/Breathing).
Detection Range: Approx 8m (Motion), 2-4m (Static/Breathing).
Interface: UART (Serial RX/TX) & GPIO (3.3V Output).
Configuration: Bluetooth (via HLKRadarTool App).
Supply Voltage: 3.0V - 3.6V DC (Strict 3.3V recommended).
Dimensions: Ultra-compact form factor (20x20mm).
Antenna: Onboard etched antenna (1T1R).
Project Evolution
Prerequisite: If you have used a standard HC-SR501 PIR sensor, you know its limitations (waving hands to re-trigger).
The Upgrade: Replacing your PIR with the LD2420 transforms your project from "Motion Activated" to "Presence Aware." It’s the difference between a light turning on when you walk in, and a light staying on until you actually leave.
Effort Level: Intermediate. Requires soldering header pins (if not pre-soldered) and using a UART-to-USB converter for initial sensitivity tuning.
Virtual Technician & Wiring Guide
⚠️ Voltage Warning: The LD2420 operates on 3.3V Logic. Do not supply 5V directly to the VCC pin or you will fry the chip instantly. If using a 5V Arduino (like Uno), use a logic level shifter or voltage divider for the RX pin. Probots™ Logic-Safe protocols recommend powering this via the 3.3V pin of your microcontroller.
Pin Mapping:
VCC: 3.3V Power Supply.
GND: Ground.
OT1: Output Pin (High = Presence, Low = Absent).
RX/TX: Serial communication for configuration/data reading.
Mounting: Radar can see through plastic casing (ABS/PLA) but not metal. Do not enclose it in a metal box!
Helpful Tutorials & Resources
Accessories & Compatibility
Included in the Box:
1x Hi-Link HLK-LD2420 Radar Sensor Module
Hardware Compatibility:
ESP32 / ESP8266: Highly Recommended (Native 3.3V logic).
Raspberry Pi: Compatible (3.3V Logic). Requires connecting to UART pins (GPIO 14/15).
Arduino UNO / Nano: ⚠️ CAUTION: Requires a Logic Level Converter. Connecting the 3.3V Radar RX/TX directly to a 5V Arduino will damage the module.
USB-TTL Adapter: Required for direct PC connection to use the "HLKRadarTool" configuration software.
Software Support:
ESPHome: Native "ld2420" component support for seamless Home Assistant integration.
Arduino IDE: Libraries available (e.g., LD2420 by various contributors).
HLKRadarTool: Official Android/iOS App (requires Bluetooth connection).
Frequently Asked Questions (FAQ)
Dimensions:


Probots sells every Electronics Part for your next Project. You can order 10,000+ Electronic Parts Online - Arduino, Raspberry Pi, NodeMCU Development Boards, Sensors, Motors, Motor Drivers, SMPS, Plastic Enclosures etc in India directly on probots.co.in
We delivery electronics components and parts throughout India using standard couriers like Bluedart, Delhivery & India Post.
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This item is covered by a warranty of 7 days from the date of delivery, against confirmed manufacturing defects only, as verified by Probots' own testing and investigation. In case of a confirmed defect, we will replace the item β a refund is issued only if a replacement can't be supplied (e.g. discontinued or out of stock). Transit damage or a wrong item received must be reported within 3 days of delivery.
If the product shows signs of misuse, tampering, physical damage, static discharge, liquid or fire damage, use of unapproved chemicals, or has been soldered or physically altered in any way.
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Probots sells every Electronics Part for your next Project. You can order 10,000+ Electronic Parts Online - Arduino, Raspberry Pi, NodeMCU Development Boards, Sensors, Motors, Motor Drivers, SMPS, Plastic Enclosures etc in India directly on probots.co.in
We offer specialized services for Bulk, Wholesale & B2B Customers like discounted prices, additional shipping options, customised products, etc . Customer with large quantity & regular orders qualify for the specialised discounted rates.
We also offer dedicated sales team to assist you with the order process by providing sales quotations, PI, technical support for choosing products, etc.
Note: Business Orders are processed manually and usually take 1-3 days to process compared to placing the order directly on our website. Please plan your purchases accordingly.
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Probots Electronics is highly regarded for its highly skilled team and knowledgeable staff who provide expert guidance to ensure customers select the right components for their technical projects. The business maintains a strong reputation for prompt service and reliable support, with many clients praising their quick response times and genuine commitment to customer satisfaction.
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