Object positioning detection circuit schematic

The object positioning detection circuit is as shown in the figure: the signal detection adopts the passive dual pyroelectric infrared sensor P2288, and a Fresnel lens is placed on the surface to improve the detection sensitivity. It detects the weak infrared energy emitted by the human body and the vehicle in a non-contact form and converts it into an electrical signal output. The object positioning detection circuit is shown in Figure 2. When the P2288 detects that a person or vehicle has entered the detection area, the P2288 generates an alternating infrared radiation signal and outputs a weak voltage signal (TTL level).

Figure object positioning detection circuit schematic

The signal is input to the dual-limit comparator after the second-stage op amp, where RW3 is used to adjust the amplification of the second-stage op amp, and RW4 is used to set the two threshold levels Uref1 (at U7) and Uref2 (at U8). When the detection voltage is greater than Uref1, U7 outputs a high level, U8 outputs a low level, then D2 is turned on and D3 is turned off, pyroelectric OUT is high level; when the detection voltage is lower than Uref2, U7 outputs a low level. When U8 outputs a high level, D2 is turned off and D3 is turned on, and pyroelectric OUT is high. When the detected voltage is between Uref1 and Uref2, both D2 and D3 are turned off, and the pyroelectric OUT is low. The amplified and shaped signals are input to the microcontroller.

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