PaPIR – a new approach to occupancy detection

A basic requirement for building automation originates in the fact that there is a need to identify the presence of people in the controlled areas.  The solution to this problem is to use some form of occupancy sensor to detect the presence of people in an area.

The occupancy sensor type most widely used in the building automation industry is the PIR ( Passive Infrared ) sensor.    PIR motion sensors use electromagnetic radiation in the low infrared spectrum in which radiation emitted by human movement is identified using a PIR detector.

However miniaturisation of PIR devices can prove problematic when compared to the usual miniaturisation of other electronic control devices.  Many of these problems arise due to the structure and characteristics of the sensor device since PIR motion detectors use thermal sensors to detect the small temperature increase present when the sensor element is exposed to radiation.  In addition the required lens array needed to the focus and detection/ elimination of any returning light sources are increasing difficult to manufacture to the necessary tolerance limits the smaller the overall size.  Of equal importance is the necessity to produce control circuits that take the lowest quiescent currents possible.  Obviously on an individual basis the power utilised in a standby mode is very small but if a larger project is considered the cumulative power taken by some hundreds ( or even thousands ) of devices can be very significant.

Some years ago Panasonic R&D investigated the developing building automation markets and set into place a design criteria that has seen a number of miniature self-contained PIR products successfully developed and introduced into many now commonplace applications. A good example – the enigmatically named PaPIR sensor – combines state of the art miniaturisation with practical specifications that allows a whole host of new applications to be realised. 

The PaPIR sensor range covers detection distances from 2m through to 12m and beyond with a versions to detect slight body movements, focused spot areas and general area movement.   This is to cover a wide area of internal building control.  Detection of movement in corridors may require a long distance version whilst occupation of a room may call for a general area type.  New applications such as repeated slight movement detection within a sheltered accommodation environment or spot check areas in doorways for counting purposes push the sensor to offer reliable detection within an often difficult environment.  Special ultra-low power versions allow long life use in remote wireless detection systems with minimal current drain taken from the power source.

Four new PaPIR products have been released from Panasonic in order to expand and complement the existing range.

The ‘Saturn’ PIR -  This unit has a lens that has two different detection areas.  An outer ring offers general movement detection with a 48 segment ring that give standard detection sensitivities.  The inner ring has 36 segments in a denser arrangement and this allows the target area to be much more sensitive so allowing slight movement detection.    An example of a typical application could be the sensor mounted in a toilet cubicle to detect occupancy.   The standard detection ring detects the entry and leaving of an occupant while the slight movement detection area detects the presence of the occupant even with very little movement.   The same scenario would apply to detection of an occupied bed.  The standard detection ring detects the movement to and from the bed while the slight movement detection area can detect the slight breathing movements of the occupier that would normally not be detected.

The ‘Hammerhead’ PIR has a rectangular sensing area, with 88 segments, in approximately a 4:1 ratio.  This allows a much better coverage of corridors, office areas and coverage of specific areas than is possible with a standard lens.  The use of covering masks and split masks extends the usefulness of the sensor is specific applications.

The ‘Lensless Pinhole’ PIR does not use a specific lens but rather uses the natural area coverage of the sensor to be utilised to achieve detection over small range.   Due to the absence of the lens a very flat head area can be achieved making the sensor ideal for mounting in a very confined space or where direct contact is made within the mounting frame.  A typical application may be to use the sensor in a door frame to identify any occupant moving through the area.  The detection distance is limited to approximately 2m however this of course is usually greater than a doorframe and so the sensor can reliably detect movement.

The ‘Pet Immunity’ PIR has an internal lens mask that can allow detection of movement above a certain height but avoid any detection below this level.  This can be very useful when used in domestic applications to help avoid detection by pets but allowing reliable detection of human occupancy.

As can be seen many new versions of the successful PaPIR sensor range are continually being developed or improved.  While the high demand for high reliability, self-contained, PIRS exists there is plenty of scope to continue to push the technical boundaries of the product and continue to meet customers’ expectations and new requirements.