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The Useful Sensors Person Sensor is a compact, pre-programmed camera-and-microcontroller module that detects nearby faces and sends structured results to another board over I2C. A host such as an Arduino, Raspberry Pi Pico, Raspberry Pi or Micro:bit reads the sensor, then decides whether to wake a display, move a servo, switch a relay, mute a microphone or send an alert. It is an input device for a maker project, not a standalone computer.
What the Person Sensor does
The module combines an image sensor with a small microcontroller. Its firmware handles the face-detection work internally, while the host receives data through a standard I2C hardware interface. Useful Sensors documents outputs that can include:
- How many people are detected.
- Where detected faces are relative to the sensor.
- Whether a person is facing the device.
- Identity and confidence information where supported by the sensor’s output.
This arrangement keeps image-processing implementation details inside the module. Your program works with detection data instead of handling camera frames or running a machine-learning model on the host.
The board uses a Qwiic-compatible I2C connector. A Qwiic cable carries power and the I2C signals to a compatible controller, reducing wiring for prototypes.
#1 Best Overall
- ACCURATE PEOPLE COUNTER SENSOR: Infrared beam technology registers a visitor only when the beam is physically interrupted — over 98% accuracy with minimal false counts from lighting changes, air movement, or shadows. A reliable foot traffic counter for retail doors and entrances.
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Documented size, software and interface
| Item | Documented information |
|---|---|
| Module type | Pre-programmed camera and microcontroller for nearby-person and face detection |
| Interface | I2C through a Qwiic connector |
| Example software | Arduino IDE, Python, CircuitPython and C/C++ |
| Official example hosts | Arduino, Raspberry Pi Pico, Raspberry Pi and Micro:bit |
| Dimensions | 19 mm × 16 mm, as listed in Make:’s December 20, 2024 review |
| Review price | $10 in that Make: review; current price, stock and seller should be checked before purchase |
Dimensions and price above describe the review sample and review date, not a permanent specification or guaranteed current retail price.
How a typical build is arranged
A practical project has four layers:
- Person Sensor: supplies presence, position and other documented face-related values.
- Qwiic/I2C connection: links the sensor to the controller.
- Host controller: runs your code and makes decisions.
- Output hardware: a display, LED, servo, relay, motor, audio circuit or network module that performs the action.
Keep the responsibilities separate: the sensor reports what it detects; the host applies thresholds, timing and safety rules; the output device performs the response.
Choosing Arduino, Pico, Raspberry Pi or Micro:bit
All four platforms appear in the official examples. Choose according to the rest of your project rather than treating one board as universally best.
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| Host | Programming path | Best fit | Check before building |
|---|---|---|---|
| Arduino | Arduino IDE with C/C++ libraries and I2C support | Fast, deterministic control of LEDs, relays, servos and other simple actuators | Available I/O, 3.3 V/5 V electrical requirements and the library’s supported board list |
| Raspberry Pi Pico | Official examples include CircuitPython and C/C++ approaches | Compact projects needing microcontroller timing and flexible GPIO | Power budget, logic levels and whether your chosen firmware exposes the required I2C pins |
| Raspberry Pi | Python and Linux-based development | Projects that also need networking, a graphical interface, logging or cloud services | Boot time, storage, power supply and enclosure space |
| Micro:bit | Use the documented I2C-oriented examples and your preferred supported environment | Educational builds and compact interactive prototypes | Connector breakout, available pins and the voltage requirements of attached hardware |
For any host, confirm the sensor’s power and logic requirements, connect I2C correctly, and avoid attaching an actuator directly to a GPIO pin unless that actuator is designed for it. Motors, relays and larger loads normally need an appropriate driver or transistor circuit.
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- Mount the sensor. Leave the camera’s field of view unobstructed and choose a position that represents the area you want to monitor.
- Connect the Qwiic cable. Plug one end into the Person Sensor and the other into a compatible host or Qwiic expansion board. If your controller has no Qwiic socket, use a suitable I2C breakout and verify voltage compatibility.
- Install the host support. Use the library or example for your selected environment: Arduino IDE, CircuitPython, Python or C/C++ as appropriate.
- Run the detection example. Confirm that the host can read the sensor and that reported person counts or face positions change when someone enters and leaves the view.
- Add decision logic. Convert readings into states such as “occupied,” “empty,” “person on the left” or “facing the device.” Add a time delay or hysteresis so an output does not chatter when readings fluctuate.
- Drive the output safely. Let the host control the display, LED, servo, relay, audio mute circuit or network request. Test failure behavior, including what happens if the I2C cable is unplugged or no person is detected.
DIY project ideas that match the sensor’s strengths
Approach-activated kiosk or display
Use a nonzero person count or a face-position threshold to wake a screen, start an animation or show instructions. Have the host turn the display off after a defined period with no detection. This saves power and keeps a public interface quiet when nobody is nearby.
Privacy-oriented microphone mute
A controller can mute a microphone or recording input when the sensor reports an empty area. Treat this as a control signal, not proof that a room is empty: test the sensor’s placement, distance and lighting, and provide a manual override.
Rank #3
- INFRARED TECHNOLOGY: The visitor counter uses infrared ray interruption technology, which provides accuracy over 98% and stability in case of minor changes in lighting conditions
- WIRELESS: The visitors counter works with batteries that can be bought anywhere
- PLUG & PLAY: The people counter is installed using supplied sticky plates or special holes in the device body
- POWERED BY BATTERIES. People Counter works more than 1 year without replacing batteries
- COUNTING BY THE HOUR: Hourly statistics provide greater detail and understanding of behavior, helps to identify patterns, plan workload, improving the efficiency of the enterprise
Person-following fan or pan-tilt mechanism
Map the reported horizontal face position to servo angles or motor commands so a fan, light or camera mount points toward the nearest detected person. Limit travel, add soft movement and include a stop condition to protect the mechanism when readings disappear.
Screen-lock trigger
The official examples include a screen-lock direction. A host can lock or dim a display after a timeout without a detected person and wake it when someone returns. Use operating-system permissions and a manual recovery path so a misread does not lock out the user.
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Face count, position or facing status can select visual effects, sound layers or animations. Keep the sensor as the input layer and put artwork, timing and actuator control on the host.
Rank #4
- Intelligent sensor design - easy to operate sensor switch, wave or touch to open and close automatically, no need to operate 5 minutes automatic operation
- All-weather auto-maintenance - Cycle purification every 3 hours, combined with 20-second cleaning and 100-second air drying to ensure a dry toothbrush
- Continuity - The toothbrush adopts Type-C fast charging technology, 5600 mAh battery, three hours fully charged, up to 160 days of battery life, not afraid of power outages
- Easy to Install - The strong backing that does not hurt the wall adapts to smooth walls, no need to drill holes, easy to complete the installation, load-bearing and firm without leaving marks
- Package Includes - 1 x 5-Person Toothbrush Cleaner, 1 x USB Cable (Adapter not included - please use 5V-1A adapter to charge the toothbrush cleaner), 1 x Wall Bracket, 1 x Backing Adhesive, 1 x Instruction Manual
Connected occupancy indicator
Publish a simple occupied/unoccupied state to a local dashboard or network service. A documented Hackaday project pairs the Person Sensor with a Blues Wireless Notecard and a host microcontroller to relay detection data to the cloud. Component availability and cellular-service costs vary, so verify those independently.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Privacy, accuracy and practical limits
The official guide includes a Privacy section, but the available documentation does not establish a universal accuracy rate, a full environmental test matrix or an independent privacy audit. Do not present a prototype as a production-grade biometric system or promise reliable identification in every condition.
- Test in the final enclosure, viewing angle, distance and lighting rather than assuming a bench result will transfer.
- Decide whether your project needs only presence, or whether using facing, identity or confidence data is justified.
- Explain to people what the installation detects and what the host does with the resulting data.
- Prefer processing and storing the minimum information needed; avoid retaining images or identity data unless your design and legal obligations require it.
- Define safe behavior for sensor errors, blocked views, unexpected faces and loss of I2C communication.
The sensor reports structured detection information to the host; your wiring, firmware, enclosure and connected services determine the project’s wider privacy and safety consequences.
Is it worth buying for a maker project?
It is a strong fit when you want a very small, pre-programmed face-detection input and already have—or plan to add—a controller and an output device. The Qwiic/I2C connection and examples across Arduino, CircuitPython, Pico, Raspberry Pi and Micro:bit reduce the amount of vision software you must build yourself.
It is a weaker fit when you need a documented accuracy guarantee, a formal biometric system, long-range or difficult-lighting performance, or a complete standalone computer. The $10 figure and 19 mm × 16 mm size come from Make:’s December 20, 2024 review; check current listings, stock, seller, power requirements and board compatibility before ordering.
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