TLV8544: Detecting object direction with dual PIR sensors

Eduardo Rey17

Part Number: TLV8544

Hello, I would like to design a circuit that outputs a logic low/high depending on the direction the object is traveling. The inputs would be from a PIR sensors since I am trying to detect human direction in realitvely close proximity (< 4ft.), the viewing angle could be as low as 30 degrees so not sure if I need a Fresnel lens. Does TI have a reference design or a starting point? What parts would be recommended for a signal chain.

over 5 years ago

0 Paul Grohe over 5 years ago

TI__Mastermind 49966 points

Hello Eduardo,

We have several TI designs, but are all based off a similar PIR circuit.

The most interesting to you would be the TLV8544 "Boost" PIR demo:

BOOSTXL-TLV8544PIR TLV8544 Quad Nanopower Op amp PIR Motion Detector Demonstration Module

In a nutshell, yes, you could determine left-to-right vs right-to-left travel.

The output of the PIR sensor is an "S" shaped waveform as the object moves through the view field.

You could determine the direction by noting if the output went zero-High-low-zero or zero-low-high-zero.

The travel must be across the face of the sensor - PIR has trouble seeing objects moving straight towards or away from the sensor.

The distance and view angle is determined by the lens. The PIR sensor requires the lens to focus the "view field" across the sensor pair. It will not work w/o a lens.

0 Eduardo Rey17 over 5 years ago in reply to Paul Grohe

Prodigy 230 points

Thank you

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TLV8544: Detecting object direction with dual PIR sensors