PIR - Passive Infrared Sensor

PIR - Passive Infrared Sensor

PIR

• Human or animals will emit heat (as infrared radiation)
• Senses infrared waves to detect motion
• Uses
  • Alarms
  • Motion sensing cameras / lights
• Not a distance sensor

PIR Specifications

• Distance range: up to 20 feet
• Detection range: ~110 degrees x 70 degrees
• Specifications vary by device and lens

Components

• Main sensor is the small metal disc which detection infrared radiation

## Components

• Clear / white lenses acts to focus a wider area of radiation onto the sensor to increase range

Operation (Sparkfun PIR)

• Requires 1-2 sec delay in setup() to get initial reading from room
• Digital output from AL pin
• HIGH when no movement detected
• LOW when movement detected
• Signal remains active low for about 3 sec after movement (documentation says 15 sec but that doesn’t seem accurate)

Other Common Parameters

• Other PIR sensors have different configurable options
  • Sensitivity (potentiometer): how much motion triggers alarm
  • Time adjust (potentiometer): how long after motion stops does signal remain active
  • Retriggering (switch / jumper): controls if alarm stays active for the same movement

Wiring

PIR (Sparkfun)	Argon
+ (red wire)	5v
- (white wire)	GND
AL (black wire)	digital input pin (with 10K pullup resistor to 5v)

Note: The wire color and pin order is specific to the Sparkfun PIR sensor and not all PIR sensor

Wiring

Exercise

• Part 1: Connect sensor; turn on on-board LED when motion is detected and turn off when motion stops
• Part 2: Create a “hold length” of 5 sec whenever movement is detected

Credit

• Sparkfun
• Diagrams created with Frizting