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Piezo film sensor for footstep detection

will_hs

I’m currently looking into detecting footsteps on a wooden floor using piezoelectric sensors and recording the output as audio.

 

After some research it seemed like a cantilever piezo film sensor might be suitable. I have ordered a few of these (MiniSense 100, LDTM-028K).

I’m wondering if there is a optimal way to mount these sensors to maximise vibrational transfer. At the moment I have soldered the sensor to a small PCB and have the PCB attached to the floor with adhesive tape. I’m amplifying the signal with a jfet preamp. I’m finding that footsteps around 6” from the sensor are barely registering above the noise floor.

 

Any advice on mounting these sensors, or even suggestions for other sensors that might be more suitable, would be much appreciated!

Thanks

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  • Hi Will,

     

    There's a photo here:

    Impact, Vibration and Ultrasound Sensing with PVDF Piezo Sensors

    where the sensor (similar to the one you've ordered I think) is slightly bent, and at a shallow angle, i.e. making an acute angle with the floor, and it seemed very sensitive (but I did have a X100 amplifier circuit). At such levels all sorts of other stuff is also picked up by the amplifier or the sensor, including 50/60 Hz electrical hum and any fans on equipment. As Doug says, any movement would need to slightly bend the sensor, and it was sensitive enough to pick up people walking on a wood floor, but I didn't investigate distance or types of wood flooring. A metre away didn't seem an issue.

    As says, an electret mic is extremely sensitive too, and enough gain should easily pick up footsteps, so it's worth considering that, and might be less experimental physically since a bare piezo film on the floor isn't practical without additional considerations. With any of these methods, probably digital processing is needed though to try to separate footsteps from other sounds.

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  • Hi Will,

     

    There's a photo here:

    Impact, Vibration and Ultrasound Sensing with PVDF Piezo Sensors

    where the sensor (similar to the one you've ordered I think) is slightly bent, and at a shallow angle, i.e. making an acute angle with the floor, and it seemed very sensitive (but I did have a X100 amplifier circuit). At such levels all sorts of other stuff is also picked up by the amplifier or the sensor, including 50/60 Hz electrical hum and any fans on equipment. As Doug says, any movement would need to slightly bend the sensor, and it was sensitive enough to pick up people walking on a wood floor, but I didn't investigate distance or types of wood flooring. A metre away didn't seem an issue.

    As says, an electret mic is extremely sensitive too, and enough gain should easily pick up footsteps, so it's worth considering that, and might be less experimental physically since a bare piezo film on the floor isn't practical without additional considerations. With any of these methods, probably digital processing is needed though to try to separate footsteps from other sounds.

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