Accelleration Sensors

Low Cost:

• Anne Ogborn says:

  Consider a small piece of solder epoxied to the needle of a phono pickup for high audio frequency accelerations.

  Consider a speaker with a lead weight glued in center and lots of holes punched for lower frequencies.

  Make an (RF) tuned circuit tuned by a small coil with a sliding slug. Suspend slug on small brass coil. Read oscillation frequency off into comparator, divider, and into pic.

  Now, a 3D version: Get a hollow cylinder and fill with alcohol (water will get bacterial growth), put a pressure sensor on each side of each axis (one at each pole and 4 on equator). Pressure on sensor is proportional to the acceleration in that direction. eliminate sensors in uninteresting directions. If you only want 1 direction, just use a length of plastic tubing, if you know the direction of acceleration.

  For a "one bit" maximum value test - suspend a ball bearing in a cage of rubber bands. If the ball falls out, you've exceeded the limit.

• Jim Vannes, Instrumentation Specialist, Information Processing Consultant, School of Education, University of Wisconsin - Madison says:

  http://www.measurementspecialties.com/vibration_dynamic_sensors.htm Measurement Specialties (formerly AMP) makes a piezo polymer vibration sensor (LDTM-028K) with an attached proof mass that functions as a cheap accelerometer: These are $.86 at Digi-Key. They put out several volts of reversing polarity as you wave them back and forth. This may be adapable as a sensor for this application. They are 1" long by .5" wide, and need some wiggle room, so they are a bit larger than an SOIC or DIP.

Archinve:

• piclist\2008\08\12\000226a "accelerometer monitoring" Low power ADC sampling of an accelerometer with the 18F1230

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