STMicro STHS34PF80 IR sensor for motion and presence detection aims to replace PIR sensors

STMicro STHS34PF80 is a new IR sensor designed for IoT and Smart Home devices requiring motion and/or presence detection that offers an alternative to traditional passive infrared (PIR) sensors and is mostly useful for building automation.

The latest IR sensor from STMicro contains thermal transistors (MOSFETs) that can not only detect motion but also stationary objects, something that’s not feasible with conventional PIR detectors that require motion for object detection. The company further adds that PIR sensors need a Fresnel lens to sense moving objects, but the STHS34PF80 detector does not require a lens and as a result, enables much smaller designs.

STMicro STHS34PF80 IR sensor

STHS34PF80 key features and specifications:

  • Range up to 4 meters without lens for objects measuring 70 x 25 cm²
  • Integrated silicon IR filter
  • IR sensitivity – 2000 LSB/°C
  • RMS noise – 25 LSBrms
  • Operating wavelength – 5 µm to 20 µm
  • Local temperature sensor accuracy – ±0.3 °C
  • 80° field of view
  • Embedded smart algorithm for presence/motion detection
    • Capable of detecting stationary objects
    • Capable of distinguishing between stationary and moving objects
  • Programmable ODRs (output data rate) from 0.25 Hz to 30 Hz, as well as one-shot mode
  • Host interface – I2C or 3-wire SPI
  • Supply voltage – 1.7 V to 3.6 V
  • Supply current – 10 µA (lower power consumption than PIR sensors)
  • Dimensions –  LGA 10-lead, 3.2 x 4.2 x 1.455 (max) mm (SMD friendly)
  • ECOPACK and RoHS compliant
STMicro IR motion presence sensor block diagram
Block diagram

The STHS34PF80 targets alarms and security systems, home automation, smart lighting, IoT devices, smart lockers, and smart wall pads. The company also mentions the IR sensor has high resistance to unwanted effects of direct lighting and high immunity to electromagnetic interference (EMI).

The STEVAL-MKI231KA evaluation kit comprised of STHS34PF80 industrial board and DIL24 adapter can be used for evaluation with the X-NUCLEO-IKS01A3 or STEVAL-MKI109V3 board using the Unico-GUI graphical interface to configure the IR sensor and take measurements. Drivers for the STHS34PF80 can be found on GitHub, and a library for compensating and detecting presence of people or objects is available in the X-CUBE-MEMS1 software package.

STEVAL-MKI231KA evaluation kit STHS34PF80 industrial board DIL24 adapter
STEVAL-MKI231KA evaluation kit

STMicro already has some products for presence detection using Time-of-Flight sensors, for instance, the VL53L5CP FlightSense ToF sensor with more advanced features such as gesture recognition and distance measurement, and they are quite more expensive (sample price: $6.88 vs $9.10) than the IR sensors. But I still asked STMicro when customers would use the IR sensor over ToF sensors and vice-versa:

An IR sensor and ToF sensor have different and complementary behaviors: while STHS34PF80 can detect human presence to about 10m with power consumption down to single digit uAs, a ToF sensor has best-in-class accuracy for distance measurement. The STHS34PF80 is therefore better suited to low power systems (always on) and extended range reach.

It is also exciting to note that, by doing sensor fusion using both devices (STHS34PF80 and ToF, see: Lock in energy and carbon reduction for occupancy detection – STMicroelectronics – when should you use an IR sensor) designers and solution creators can achieve the best performance possible for presence sensors using the STHS34PF80 to wake up the ToF sensor when human presence is detected. This can contribute to saving energy and to only doing very accurate analysis (and consume more power) when it is necessary.

The article linked in the response from STMicro also has a handy table comparing the main strengths and weaknesses of IR sensors against Time-of-Flight (To), PIR, and ultrasonic sensors.

IR sensor vs ToF vs PIR vs Ultrasonic

The STHS34PF80 is in mass production now with the price starting at $2.60 for orders of 1000 pieces, and more when getting a few samples. More details can be found on the product page and the STEVAL-MKI231KA evaluation kit is sold for $35 on Mouser.

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