I. Solution Overview
An ultra-thin single-point thin-film pressure sensor is selected and attached to the surface of the door handle. By collecting the grip pressure signal, the door handle status is sensed in real-time. The solution focuses on low cost and easy deployment, making it suitable for various fields such as security monitoring, smart home monitoring, and health care.
Core Device Combination:
Core Working Principle: The RP-L110 sensor is a resistive pressure-sensitive element. When no pressure is applied, the resistance is infinite. When pressure is applied, the resistance decreases as the pressure increases. The CMCU-05/05A collects the resistance change and converts it into AD values and pressure values. The wireless transparent transmission board sends the data remotely to the terminal, realizing a complete chain of "sensing - collection - transmission - recording".
Sensor Installation Position Scheme: Attached to the surface of the door handle
When a person holds the handle naturally, the thumb or the crotch of the hand contacts the upper edge area, exerting force naturally. The experimental test uses the upper edge surface, which can be attached to the inside or outside.
II. Measurement Scheme
2.1 Measurement Principle
The sensor is normally in an untriggered state (resistance > 10MΩ). When a person holds the door handle, the sensor senses pressure, and the pressure value changes. According to the pressure value, the strength of the grip can be roughly distinguished based on the force applied by the person opening the door, helping to identify the operator type (e.g., adult/child). A "door opening operation" is recorded when a pressure change is detected.
When the pressure sensed by the sensor exceeds the trigger threshold (threshold is adjustable), the CMCU-05/05A acquisition module will issue an alarm signal (the on-board threshold LED lights up, and a 3.3V high-level voltage signal is output). This can be used to connect a relay to control the switching circuit. (A small experiment where an LED lights up upon door opening will be demonstrated below.)
2.2 Key Parameters
Sensor (RP-L110):
- Sensing Range: 20g~10kg
- Thickness: 0.35mm, flexible structure, can fit curved surfaces
- Durability: Over 1,000,000 cycles
- Operating Temperature: -40℃~+85℃
Single-Channel Thin-Film Pressure Transmitter (CMCU-05/05A):
Wireless Transparent Transmission Board:
- Converts data into wireless signals for remote data transmission
Main Parameters: Uses a 433M wireless RF solution, offering long transmission distance and good wall penetration. In open areas, the measured maximum distance can reach up to 500 meters. With the default antenna, the measured distance is 200 meters. Supports external suction cup antennas and RF antennas to increase the distance.
2.3 Data Collection Process
- Sensor Force Applied → Signal Change
- CMCU-05/05A Acquires → Converts to Pressure Value
- Pressure Value Exceeds Set Threshold → Trigger Recording
- Wireless Transparent Transmission → Remote Terminal Records Timestamp and Pressure Curve
III. Experimental Process
This article mainly explains the experimental process and data interpretation. For those who want to see the actual operation and the full process of the equipment in action, you can jump to the Bilibili video: https://www.bilibili.com/video/BV12ijA6AEoZ/?spm_id_from=333.337.search-card.all.click
3.1 Preparation Before the Experiment
3.1.1. Sensor Attachment: Attach the thin-film pressure sensor to the upper surface of the door handle, and use double-sided tape or adhesive tape to fix the sensor position to prevent displacement.
3.1.2. Lead Connection: Connect the sensor leads to the CMCU-05/05A acquisition board。
3.1.3. Connect the wireless transparent transmission receiver to the computer via USB.
3.1.4. Equipment Debugging: Power on and pair, confirm that wireless communication is normal.
3.2 Experimental Procedure
3.2.1.Threshold Confirmation: Perform a pressure level test on the sensor, select a threshold trigger value, and set the trigger threshold in the software.
3.2.2.Door Opening Test: There is no pressure value before gripping the door handle. Record the pressure value when touching the door handle, and the pressure value when gripping and opening the door handle. Repeat the operation more than 10 times and observe whether the threshold signal is successfully triggered each time.
3.2.3.Data Recording: Each door opening operation automatically records the timestamp, forming a door opening event log, and confirming that each door opening record is correctly uploaded.
The following data were obtained from actual door handle gripping tests (sensor attached to the upper edge):
- Different handle materials, installation angles, sensor sizes, and other factors will affect the data results.
Ⅳ. Application Scenarios
4.1 Home Security and Daily Monitoring
- Front Door Opening Records: Real-time recording of family members' entry and exit times, can be linked with an APP to push door opening alerts.
- Refrigerator/Cabinet Monitoring: Attach to the compression surface where the refrigerator door frame contacts the cabinet body. Use the compression pressure when the door is closed as the "door closed" signal; if the door remains closed beyond a set time (e.g., 5 minutes), a mobile phone alarm is triggered to prevent cold air leakage and food spoilage.
- Child/Pet Behavior Tracking: Monitor door handles of snack cabinets, study rooms, etc., allowing parents to know if a child has opened a cabinet door during a specific time period.
4.2 Health Care and Elderly Care
Activity Monitoring for the Elderly Living Alone: Record the frequency and time periods of bedroom and bathroom door openings. If no door opening action is detected for 8 or 12 consecutive hours, automatically send an alert to children or the community. Compared to wearable devices, this "unobtrusive monitoring" method is more easily accepted by the elderly and will not fail due to forgetting to wear the device.
Medication Adherence Tracking: Attach to medicine cabinet locks or bottle caps, record the daily time of opening the cabinet to take medication, assisting in determining whether the elderly person is taking medication on time.
4.3 Commercial and Public Spaces
Player Behavior Statistics (e.g., Escape Rooms): Attach to game-specific items, door handles, etc., to sense player progression and item usage in real-time, count the number of uses, and assist in analyzing game completion paths and operating habits.
Office Space Management: Monitor the usage frequency of meeting room doors and pantry doors, providing data support for space utilization analysis
4.4 Education, Research, and DIY
University electronic design teaching: as a typical teaching case for flexible sensing and embedded development, helping students understand the sensor signal chain
Maker project basic module: can be expanded to connect to platforms such as Raspberry Pi and Arduino for developing various interactive devices
V. Application Areas
VI. Application Prospects
6.1 Market Positioning: Differentiated Supplement
The current smart lock market has become mature, but it mainly covers the "lock control" level - achieving advanced functions such as remote unlocking and fingerprint recognition. This solution is not only used for induction monitoring but also for behavior analysis.
- No need to replace the door lock, stick and use immediately
- Controllable cost (total cost of sensor + collector + transparent transmission board is about a few hundred yuan, far lower than that of smart locks)
- Applicable to all doors with handles, not limited to main entrance doors
6.2 Expansion Directions
Multi-node networking: A single host can connect to multiple collection points (main door, refrigerator, medicine cabinet) to build an overall household behavior log;
Pressure curve analysis: The grip force curves of different users vary. Combined with simple clustering algorithms, it can assist in identifying the operator's identity;
Cloud platform integration: Push data to open-source platforms such as Home Assistant and Node-RED via serial port or wireless gateway to achieve linkage with other smart devices.
6.3 Commercial Potential
It has clear commercial value in the elderly care monitoring niche market. Against the backdrop of China's accelerating aging population, the demand for low-cost, unobtrusive home-based elderly care monitoring devices continues to grow. This solution achieves 24-hour uninterrupted door activity monitoring with hardware costs under one thousand yuan, offering a significant cost-effectiveness advantage compared to smart security kits that often cost thousands of yuan.
VII. Summary
This solution takes the RP-L110 flexible film pressure sensor + CMCU-05/05A single-channel pressure collector + wireless transparent transmission board as the core, integrating pressure sensing, threshold judgment, signal output, and wireless return into a concise technical path. Following the operating steps and measured reference data provided in this document, debugging personnel can complete single-point deployment and put it into practical use within 30 minutes.
Core value: Use inconspicuous sensors to address everyday aspects - making every "door opening" meaningful.
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