Geophones for Under $50
by: Jonathon Vanover
This month, I have an easy project that makes a useful piece of equipment that can be assembled for under $50. A geophone is a device that detects motion and outputs it as an electronic signal. They are used to detect earthquakes and vibrations - so they have many uses. So why build one instead of buying one? I have seen them sell for as much as $200 from ghost supply companies…which is absolutely ridiculous when you can assemble your own for around $50. In the field of paranormal investigation, they can be placed on a floor where footsteps have been heard to see if the noise is actually coming from a physical reaction or something else.
So how do we build this device? A company called BG MICRO (http://www.bgmicro.com) sales a geophone and display circuit as a simple kit for $43. I bought one of these and assembled it into a plastic box when I lived in Philadelphia in an apartment building next to the public rail system. This device would detect a passing train even when I could not hear it or feel it, so I know they work really well.
Parts List:
Geophone Kit (BG MICRO part number KIT1019) $43
9 vdc battery clip (Included with KIT1019)
9 vdc battery $1.00
50 KOHM (BG MICRO part number RES1063) $1.53 (optional part)
Plastic box (repurpose something or buy one from Radio Shack or BG Micro for $7 to $10)
Connections and jumpers:
J1 is used to select bar or Dot mode. Connect the jumper to get bar mode
J2 is the power connection
J3 is where you connect the geophone sensor
R1 is used to adjust the sensitivity