Posted by Landolf Theron | 19 June, 2019


Occupancy detection systems are widely used as a security mechanism and to detect human presence for automatically controlling room temperature, lighting or ventilation. A key factor to an effective alarm system is to ignore to the presence of small dogs. The ProxFusion® series allows for implementing pet immunity, while reducing the number of analogue components used in conventional PIR alarm systems.

How Pet Detection works

ProxFusion® is a range of multi sensor IC’s. A single ProxFusion® IC can control up to two PIR sensors. A Fresnel lens is used to project the IR onto the PIR elements as seen in Figure 1. The field of view and range of the dual PIR sensor is dependent on the type of Fresnel lens used.

Figure 1: PIR Fresnel Lens

The dual PIR detection setup is shown in Figure 2. The aim is to create two unique detection zones: one for pets and one for adult humans. This is done by directing one Fresnel lens upwards and one downwards. Small dogs will only trigger the bottom facing PIR sensor (lower zone), while both PIR’s will be trigged by an adult human.

Figure 2: Dual PIR Setup

It is recommended to place the sensor at a height of 1.7m as this will allow enough black body radiation from an adult to trigger the top PIR sensor, while not triggering the sensor when a pet in the detection zone.  The best placement for a motion sensor is in a corner of the room, as this allows the sensor to monitor the entire room. The data displayed in Figure 3 and Figure 4 shows the delta values for the top and bottom PIR sensors, calculated as: Delta = Counts – LTA

Typical human movement causes large fluctuations in both the upper and the lower PIR sensor readings simultaneously. Both PIR sensors receive a large change in in the measured IR signal, due to the large amount of black body radiation emitted by humans.  The received signal on the top PIR sensor from a pet’s movement is significantly smaller than any human movement. When implementing a sensor trigger for the PIR sensor, the threshold needs to be set above the max pet signal received. The threshold on the top PIR sensor can be set more sensitive than the bottom.

Figure 3: Human walking upright at four meters in front of sensor.

Figure 4: Pet moving 1-6m from sensor

Reduced BOM

ProxFusion can integrate up to six sensors in a single IC. This reduces the amount of analogue components and finally assembly costs.

Add Tamper Detect

The same ProxFusion IC can detect any alterations made to the cover of the device. If a conductive material is used to the cover the device a change in the distance will effect the capacitance that is measured by the IC (see Figure 5).

Reduced Power Consumption

When implementing the IQS62x IC’s in battery driven PIR sensors, it is possible to configure the sensor in event mode, which will immediately transmit data once movement is detected.

To summerize

The IQS62x series have several advantages over conventional PIR sensing circuitry:

  • Raw data output for smart DSP algorithm
  • Adjustable sensitivity (gain) via I2C
  • Less components required
  • Smaller PCB and less PCB layers required
  • Multiple features (PIR/tamper detection/magnetic switch) on one IC
  • Two PIR elements using one IC – useful for pet immunity
  • Low power consumption
  • Less MCU processing required
  • Improved tamper detection

The inclusion of machine learning and AI could potentially increase the effectiveness and accuracy of the test setup. Different signatures for different types of motion could potentially be assigned, that would allow the sensor to distinguish between various factors such as human walking direction or child detection.

About the author

Landolf Theron is an Application Engineer with three years’ experience in various specialty sensor applications, including Rotational Hall-effect, Inductive and Capacitive sensing. He holds an MEng degree in Biomedical Engineering and currently works at the Azoteq R&D Headquarters in South Africa. Landolf can be reached at [email protected].

The IQS269A is Azoteq’s latest ProxFusion® IC and can monitor the sensors listed below at the same time:

  • 2 x PIR Sensors – Motion/pet detection
  • 1 x Inductive Sensor – Used for window/door opening detection
  • 1 x Piezo Element – Can detect window breaking
  • 1 x Touch Button – User Interface
  • 1 x Tamper Detection