Seeed Studio MR24HPB1 Human Presence Radar
Introduction
This document focuses on the use of the radar, the issues that need to be addressed at each stage to minimise design costs and increase product stability, and improve the efficiency of project completion. From hardware circuit reference design, radar antenna, and housing layout requirements, how to differentiate between interference and multi-functional standard UART protocol outputs.
The radar is a self-contained space sensing sensor, consisting of RF antenna, radar chip and high speed main frequency MCU together with a module that relies on a stable and flexible superior algorithm architecture core to solve the user’s various scenario detection needs, which can be equipped with a host computer or host computer to flexibly output detection status and data, meeting several groups of GPIOs for custom development.
Principle of Operation
The radar transmits a millimetre wave signal in the 24 GHz band, the measured target reflects the electromagnetic wave signal and demodulates the transmitted signal, which is then amplified, filtered, and processed by ADC to obtain the echo demodulated signal data. The amplitude, frequency, and phase of the echo signal are decoded in the MCU unit, which ultimately enables the measurement of target parameters (breathing, movement, micro-motion, etc.) and scene evaluation.
Hardware Design Considerations
The radar needs to have a rated supply voltage of 4.9 – 6V and a rated current requirement of 200mA or more under normal operating conditions. The power supply must be designed for a supply ripple of ≤ 100mv.
- The power supply can be designed with the following circuit in mind.
Wiring Diagram
Antenna and Housing Layout Requirements
- PCBA: The radar needs to be kept ≥ 1mm higher than the other components. Housing construction: need to maintain a distance of 2 – 5mm between the radar antenna face and the housing face.
- Housing detection surface: non-metallic housing, needs to be flat and straight to avoid curved surfaces, which can affect the performance of the entire swept surface area.
Static Protection
Radar products have electrostatically sensitive circuitry and are susceptible to electrostatic hazards; therefore, they need to be adequately protected from static electricity during transport, storage, work, and handling. When handling the radar sensor, please wear anti-static gloves if possible.
Functional Disturbances
Unoccupied state, abnormal output occupied. Under normal conditions, the radar will accurately detect the presence of a sitting or sleeping body and provide information on falls, breathing, vital signs, etc.
- The radar scanning area is large: the doorway and the boarded wall next door. Movement is detected.
- Adjustment method: reduce radar sensitivity, and radar provides scene setting.
- The radar underneath is facing a running air conditioner or fan.
- Adjustment method: the radar position so that it is not directly in front of the air conditioner or fan.
- Shifting objects caused by air conditioning winds.
- The radar is not fixed; vibration causes false alarms. Avoid supporting shaking and vibration.
- Occasional moving objects such as pets, birds, etc.
- Power supply interference results in occasional false alarms.
Try to keep the power supply current stable and reduce ripple.
Manned Status, Abnormal Output Unoccupied
Radar determines the presence of a human body by sending and receiving electromagnetic waves. The closer you are to the radar, the more accurate it is.
- The human body is out of radar range.
Radar scanning range with adjustment of mounting angle. Radar measurement ra.In different environments with different electromagnetic wave reflection areas, the scanning area will vary slightly.
- False output due to metal occlusion
Excessively thick desks and chairs, metal seats. It will block the electromagnetic wave penetration and cause misinterpretation.
- Differences in scanning angles
The radar does not scan the torso area. This can lead to false positives.
- Radar sensitivity is too low.
The radar offers parameter adjustment to increase sensitivity for improvement.
Function Point Descriptions
| Functions | Status change time/function explanation |
| DP1: occupied/unoccupied | No one to occupied, report within 0.5s Manned to unoccupied, no status output in 1-2 minutes or so |
| DP2: Some people are stationary / some people are active | Static dynamic switching, reporting within
0.5 seconds |
| DP3: Someone close to the device/someone moving away from the device/someone moving without direction | Status output once every 2 seconds |
| DP4: Body movement amplitude parameter 0 – 100 | Data output once every 5 seconds Reference (description of output of body motion amplitude parameters) |
| DP5: Sensitivity setting 1 – 10 steps | Default scene mode, adapted to 10 positions of adjustment |
| DP7: Scene modes (bed, bathroom, hotel, bedroom, office, default mode) | Adapted to different scenarios according to the size of the area |
| DP8: No false alarm confirmation prompt |
Body Movement Amplitude Parameters
| 0% | None | Environmental unmanned |
| 1% | Stationary (sleep) | Only breathing without body movement |
| 2% – 30% | Micro-Movements | Only minor head or limb movements Movement |
| 31% – 60% | Walking/fast body movements | Slower body movements |
| 61% – 100% | Running/close-range big moves | Rapid body movement |
Description of the Agreement
- Interface level: TTL
- Baud rate: 9600bps
- Stop bits: 1
- Data bits: 8
- Parity: None
Communication Commands and Parameter
Frame structure definition
| Starting Code | Length of data | Function codes | Address code 1 | Address code 2 | Data | Check Code | ||
| 0X55 | Lenth_L | Lenth_H | Command | Address_1 | Address_2 | Data | Crc16_L | Crc16_H |
| 1 Byte | 1 Byte | 1 Byte | 1 Byte | 1 Byte | 1 Byte | n Byte | 1 Byte | 1 Byte |
Description of the frame structure
- Start code: 1 Byte, fixed to 0X55.
- Data length: 2 bytes, low byte before, high byte after. Length = Data Length + Function Code + Address Code 1 + Address Code 2 + Data + Checksum.
- Function code: 1 Byte
- Read command: 0X01
- Write command: 0X02
- Passive report command: 0X03
- Active report command: 0X04
- Address code: Address code 1
- indicates the function classification, and address code 2 indicates the specific function.
- Data: n Byte
- Checksum: 2 bytes, low byte before, high byte after.
Address Assignment and Data Information
24G Bio-aware radar interface contentÂ
| Function Code | Address code 1 | Address code 2 | Data | Notes | |
| 1 | Read command 0x01 | Marking search 0x01 | Device ID 0x01 | — | — |
| 2 | Software version 0x02 | — | — | ||
| 3 | Hardware version 0x03 | — | — | ||
| 4 | Protocol version 0x04 | — | — | ||
| Radar
Information Search 0x03 |
Environmental status 0x05 | — | — | ||
| 11 | Signs parameters
0x06 |
— | — | ||
| 12 | System parameter search 0x04 | Threshold gear 0x0C | — | — | |
| Scene setting 0x10 | — | — | |||
| 16 |
|
|
Threshold gear 0x0C | Enumeration range1~10 | Corresponding to 1 2 3 4 5 6 7 8 9 10 gears (default 7). The higher the gear, the more |
Description
- The read/write command is for the upper computer to send commands to the radar.
- The report command is for the radar to send information to the upper computer.
- Fall sensitivity is 1~10, default is 4; the higher the level, the more sensitive it is.
Historical Version Update
| Revision | Release Data | Summary |
| V1.0_0212 | 2020/02/12 | First draft |
| V1.1_0319 | 2021/03/19 | Readjustment |
| V1.3_0628 | 2021/6/28 | Add Human sensitivity explained and fall sensitivity explained |
| V1.4_0906 | 2021/9/06 | Human sensitivity revised from 0-9 to 1-10 |
Customer Support
- Website:Â www.seeedstudio.com
- Ph:Â +86-0755-86095676
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