LPPS Geophone/Vibration Sensor

We’ve all been there, we heard a loud bang, felt the floor/bed/table shake, ect., but other then our own perception we didn’t really have a way to show it happened. There are, for sale, devices called Geophones or Vibration sensors, but these get very expensive very quickly and can be very limited in where they can be used.

What most of these do is they convert vibrations into electrical signals. The ones used for ground vibrations to detect tectonic plates typically use a pair of springs in a cylinder, a magnet between the springs, and copper or some other conductive material coils around the magnet. As the magnet moves inside, it produces electrical voltage which is then read to determine how much movement has occurred.

Another type is called Piezoelectric which operates in a very similar fashion. Movement of a center of the piezoelectric causes an electrical current to be formed which can be measured to determine how much vibration has occurred.

The down side to both of these is that you need to have an external module for the sensor, PLUS the reading device. The weighted cylinder version requires it to be anchored to a stationary object, and the piezoelectric one has to have the center disk be in contact with the surface you are measuring the vibrations from. Both only measure on a single axis X which is up and down.

In recent years however, the piezoelectric disks have evolved into accelerometers. An accelerometer is, for simplicity sake, essentially a piezoelectric disk embedded into an chip which measures pressure asserted against the embedded disk. Most accelerometers are 3 axis (X, Y, Z) which translates to 3 different disks measuring force from different angles which produces movement in 3D space.

This makes an accelerometer the perfect thing to use to make a vibration sensor. By placing it inside of a computer chip it can measure the forces asserted against the chip itself in all directions. Dedicated devices based on an accelerometer are still insanely expensive as most are made for heavy industrial use.

So we decided to build our own and here are the results.