Introduction
Automatic doors rely on sensors to detect approaching people and trigger the door mechanism. PIR sensors are a popular choice due to their low cost, reliability, and ability to detect warm bodies.
Types of Automatic Door Sensors
- PIR sensors: Detect body heat and motion.
- Microwave sensors: Detect motion via Doppler radar.
- Pressure mats: Detect weight on mat.
- Push buttons: Manual activation.
- Safety sensors: Prevent door from closing on person.
PIR Sensor Placement for Automatic Doors
Approach Detection
One or more PIR sensors are mounted above the door, angled outward to detect people approaching. Typical detection zone: 2-4 meters in front of door, 2-3 meters wide.
Safety Sensors
Additional PIR sensors may be mounted to detect presence directly under the door to prevent closing on a person. These have a downward-facing narrow field.
Detection Zone Design
The approach detection zone should:
- Cover the expected path of approaching people.
- Not extend too far (to avoid false triggers from passersby).
- Have defined boundaries to minimize false triggers.
Integration with Door Controller
The PIR sensor output (typically relay or open-collector) connects to the door controller. When motion is detected, the controller activates the door motor.
PIR Sensor OUT ────┬──── Door Controller Input
└──── Pull-up resistor (if open-collector)
Timing Considerations
- Hold time: How long door stays open after last detection. Typically 2-10 seconds adjustable.
- Re-trigger: Should re-trigger if person lingers.
- Close delay: After hold time, door closes.
Safety Standards
Automatic doors must comply with safety standards:
- ANSI/BHMA A156.10: Power-operated pedestrian doors.
- EN 16005: Power-operated pedestrian doorsets.
- UL 325: Door, drapery, gate, louvers, and window operators and systems.
These standards require redundant safety sensors and fail-safe operation.
Redundancy Requirements
For safety, automatic doors often use dual technology (PIR + microwave) or multiple sensors so that failure of one sensor doesn’t cause a hazard.
Environmental Considerations
- Outdoor doors: Sensors must be weatherproof (IP65+).
- Temperature range: Must operate in local climate extremes.
- Sunlight: Direct sun can cause false triggers; use shaded mounting.
Case Study: Supermarket Entrance
A supermarket installed PIR sensors above each automatic door. The system used dual sensors per door (for redundancy) and achieved 99.9% reliability over two years.
Conclusion
PIR sensors are a reliable, cost-effective choice for automatic doors. Proper placement, zone design, and adherence to safety standards ensure safe and convenient operation.