Infrared human body detection circuit

The infrared human body detector uses an infrared sensor , which can detect changes in infrared energy emitted by objects in a non-contact manner and
convert it into electrical signal output. Its packaging usually comes in two forms: metal packaging and plastic packaging. Pyroelectric infrared sensors are distinguished from the internal structure
and have two types: single element and dual element. The dual-element type receiving wavelength is 6.5-14ym. Suitable for human body sensing of boat theft system. The single-element receiving
wavelength is 1-20ym, which is suitable for temperature remote sensing, but can also be used in anti-theft and automatic control systems.
    In order to improve the receiving sensitivity of the pyro infrared sensor, a Fresnel lens is usually added in front of the sensor, so that a large number of infrared light pulses
enter the pyro infrared sensor , thereby increasing the control distance, which can generally reach more than 10m. Shown in the picture is a dual-pulse infrared human detector
. This circuit uses a dual - element pyroelectric infrared sensor as the detector of the circuit. When the detector receives the human body signal, it outputs a
weak low-frequency signal with a frequency of about 0. 3 ~ 3 Hz. A 1-4 and A 1-3 form a two-stage low-pass filter amplifier. A1-1 and A1-2 form a window
comparator. A 2-1-A 2-4 constitute a single-limit comparator. U. A high level on the terminal indicates there is an output signal. The Uoi terminal can be used to detect slowly changing signals.