Accelerometer Sensitivity For Human Proximity?

Community General Discussions
, ,
1

I have a family of squirrels that visit my yard most days, and it is clear they are spying on me. How do I know?

The squirrels like to lay, (in the shade), prostrate on the patio. I have discovered that they will turn their heads toward me in two circumstances: 1) I strike up a conversation with my wife (inside the house 30 to 50 feet from the squirrel), or 2) When I walk, (inside the house, barefoot), toward the squirrel 15 to 20 feet away.

My house is built on a concrete slab, which (clearly) transmits vibrations to the squirrels.

I have done some cursory programming to use my robot’s microphone as a sound level proximity sensor using average and peak sound statistics, but was not impressed by my skills with this sensor.

My robot does not have an accelerometer to investigate this use as a proximity sensor.

One of the common robot accelerometer spec sheet states 1mg sensitivity in 2g mode with 0.2mg noise, 0.5mg/degC temperature drift, and +/-40 zero-g bias.

Is this sensitive enough to detect a human approaching to within 5 feet of a robot sitting quietly on a hard surface flooring of a home?

(My robot sensor philosophy is to maximize usage of as few sensors as possible, because every new sensor is a distraction from the holistic focus I want. The PiCamera is currently my robot’s most sensitive proximity sensor, but is also a resource and power hog, so using a layered proximity sensor approach might be beneficial.)

2

Found this research on footsteps measured at 1 meter - 0.001 to 0.002 g peaks so “hobby” accelerometers are probably not useful for footstep detection: https://www.researchgate.net/publication/241517823_Vibration_signature_of_human_footsteps_on_the_ground_and_in_buildings

1 Like
3

Hi @alanmcd, it’s nice to see you in the forum :slightly_smiling_face:

Proximity detection can be a difficult task with an accelerometer because, as you said, hobby models aren’t sensitive enough to detect small vibrations.

If your goal is to detect the presence of someone or something I would recommend a PIR sensor which is a simpler solution and its sensitivity can be adjusted to detect both people and animals, you can find some options here. Another option could be using a piezo sensor like these, you can see how you could use one in this blog.

And as you said you already have a PiCamera other option could be applying an object detection algorithm, that way the camera could be used to detect different objects, such as people or animals. Also with the correct location or with the use of more than one camera you could approximate the location of them in your yard (yeah, those squirrels won’t be able to do such a good job spying anymore :joy:).

2 Likes