Automatic Doors: Seeing the Invisible

You approach the sliding glass doors at Target. They glide open. They don’t have eyes. They have PIR (Passive Infrared) sensors or Microwave Radar.

PIR: Detecting Heat

A PIR sensor looks for Change in Heat.

• The background (pavement) is 70°F.
• You (a human) are 98°F.
• As you walk into the sensor’s view, the Infrared energy spikes.
• The chip sees the spike and triggers the motor. “Open Sesame.”

Radar: Detecting Motion

Newer doors use Doppler Radar.

• They emit microwave pulses.
• The pulses bounce off objects.
• If an object is moving towards the sensor, the frequency shifts (Doppler Effect).
• This is better because it doesn’t get confused by hot pavement on a sunny day.

Robotics: The Break Beam

In our robots, we use a simpler version called a Break Beam.

• Emitter: Shoots an invisible beam of light across the intake bucket.
• Receiver: Sees the light.
• Logic: As soon as a game piece enters, it blocks the beam. The Receiver sees darkness.
  • if (BeamBroken) { StopIntake(); CloseClaw(); } This allows the robot to “feel” when it has successfully grabbed an object without the driver pressing a button.