How to detect stationary human body in smart home?

At present, detecting and judging whether smart homes mainly use infrared, radar, and ultrasonic waves, so what are the advantages and disadvantages of these sensors?

The infrared sensor is used to detect whether there is a human body in the area. When the human body is still, the infrared sensor cannot detect the human body.

1. Human presence sensor (micro motion sensor)

In order to detect static human body (sleeping or sitting person), smart home products now introduce a new sensor (micro-motion sensor), the basic principle of which is to detect human breathing, heartbeat and micro-peristalsis of organs.

To achieve such high precision, detecting the peristalsis of organs through skin and bone requires the use of higher detection accuracy, which can penetrate non-metallic radar sensors.

2. Radar sensor

When it comes to radar, many people think of the car’s reversing radar. In fact, the car reversing radar is actually an ultrasonic ranging sensor, a bionic bat that uses the time of ultrasonic reflection to judge the distance between the car and obstacles.

Pulse radar and related radar are actually used to judge the presence of human body.

When an object moves in the sensing area (defense area) of the Doppler effect radar sensor, the waveform of the radar signal will change, thereby triggering the radar sensor circuit.

Radar sensors can penetrate non-metallic obstacles, so they can be installed concealed and are more flexible than infrared sensors.

However, radar sensors using the Doppler effect are still unable to detect static human bodies due to their low accuracy;

And because the radar sensor can see through non-metallic obstacles, if your deployment is not in the right place, the old king next door may walk around the house to trigger the radar sensor, or even the neighbors upstairs.

3. PCR radar sensor

The PCR (Pulse Coherent Radar) sensor is a sensor that detects millimeter-level movements with high precision using high-frequency millimeter waves.

The chip combines pulse radar and related radar, which can be used to judge the small vibration of organs when the human body is still.

However, the distance that can achieve static human body detection is only about 2 meters, and the distance that can detect motion can reach about 4 meters.

In fact, since infrared detection requires human body movement to detect, then if the person does not move, the infrared detector can be moved. So he installed the infrared detector on the cloud platform and let the infrared detector rotate. As long as there is someone within the detection range, it can detect whether you are moving or not.