Passive infrared device for detection of boundary crossings

A system for detecting the average speed of an individual through a pathway, the system comprising:

• a) a first PIR sensor positioned in the pathway, the first PIR sensor defining a first detection zone and operable to produce a first output waveform when the first detection zone is crossed;
• b) a second PIR sensor positioned in the pathway a defined distance from the first PIR sensor, the second PIR sensor defining a second detection zone and operable to produce a second output waveform when the second detection zone is crossed;
• c) a first processor connected to the first PIR sensor, the first processor operable to estimate a first boundary line crossing based on the first output waveform;
• d) a second processor connected to the second PIR sensor, the second processor operable to estimate a second boundary line crossing based on the second waveform;
• and
• e) a central controller in communication with the first processor and second processor, the central control operable to calculate an average speed through the pathway based on the time of the first boundary line crossing and the time of the second boundary line crossing.

A device for detecting a boundary crossing comprising:

• a) a PIR sensor having two pyroelectric elements, the PIR sensor operable to produce an output waveform having a zero crossing;
• b) a bandpass filter and amplifier connected to the PIR sensor and operable to filter and amplify the output waveform;
• c) a comparator connected to the bandpass filter and amplifier, the comparator operable to provide a response when the output waveform is greater than a first threshold or less than a second threshold;
• and
• d) a processor connected to the comparator, the processor operable to estimate the zero crossing of the waveform based on the response of the comparator, the zero crossing providing an estimate of the boundary crossing.

A method of determining a boundary crossing comprising the steps of:

• a) providing a PIR sensor having a first pyroelectric element and a second pyroelectric element, the first pyroelectric element operable to monitor a first detection zone and produce a positive signal when the first pyroelectric element detects a change of infrared radiation in the first detection zone, the second pyroelectric element operable to monitor a second detection zone and produce a negative signal when the second pyroelectric element detects a change of infrared radiation in the second detection zone, wherein the positive signal and the negative signal are combined to provide an output waveform;
• b) determining the zero crossing of the output waveform;
• and
• c) estimating the boundary crossing based on the zero crossing of the output waveform.

A method of detecting the average speed of an individual through a pathway, the method comprising the steps of:

• a) providing a first PIR sensor positioned in the pathway, the first PIR sensor defining a first detection zone and operable to produce a first output waveform when the first detection zone is crossed;
• b) providing a second PIR sensor positioned in the pathway a defined distance from the first PIR sensor, the second PIR sensor defining a second detection zone and operable to produce a second output waveform when the second detection zone is crossed;
• c) analyzing the first output waveform and estimating a first boundary line crossing based on the first output waveform;
• d) analyzing the second output waveform and estimating a second boundary line crossing based on the second output waveform;
• and
• e) calculating an average speed through the pathway based on the time of the first boundary line crossing and the time of the second boundary line crossing.