PIR Sensor Development

The PIR sensor tracks movement by probing infrared in the room. Output changes to high when motion is detected and low when no motion is detected.

We tested the sensor's field of view, sensitivity, and data integrity over long wires. Some tests we did were:

• Gradually moving away and towards the sensor to see at what distance where motion would be picked up
• Attaching the sensor to the ceiling because this is where it would be once the project is complete. This will ensure a good field of view (140 to 160 degrees).
• Flashing LED and incandescent lights at the sensor
• Moving in an exaggerated manner in front of the sensor
• Moving very subtly in front of the sensor
• Sitting still in front of the sensor

• The sensor has detection radius of about 20 feet as advertised.
• Digital signals were preserved over long wires (not sure about analog which might be more susceptible to problems)
• The sensor can only detect significant motion. If someone is studying and not moving a lot, it might not sense any changes and might believe the room is empty.
• The sensor will not go off if someone's sitting very still
• The sensor is immune to (low intensity) LED and incandescent light sources

Although the PIR sensor worked as expected, ketty and blackthroat found out later through testing that the placement of the sensor is very important. The PIR sensor was originally placed at the center of the room affixed to the ceiling but this was not a good place because although the sensor had a long range of view, it did not have a wide viewing angle. The solution was to put the sensor in the middle of the wall at about 4 feet from the floor so it viewed the room lengthwise.

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