cheap accelerometers?

Depending on how cheap, how many, and how much work you are willing to do....

I've played a bit with using a 2cm pizo buzzer element in it's plastic case as an accelerometer. Cover up the holes with thick duct tape, make sure there are air channels for air to move between the two sides, maybe glue a bit of weight to the center of the disk, calibrate the heck out of it. (which will be the toughest bit)

This could be useless to you, or a way to save some money...

Al...

Dear Greg Locock:

It'll depend on the frequency, and the internal construction...

And good ideas yourself...

David A. Smith

When I was playing around, I was very clearly seeing my hand wave gently back and forth on a scope, no amp, no weight glued on. Very directional. I never carried the project further to see how predictable I could make the output though...

Al...

How about a strain gauged cantilever with a weight on the end?

Or a loudspeaker coil with a weight on the cone?

Or a mass on a spring with a solenoid and a magnet (same as the loudspeaker).

You'll need to do a bit of signal conditioning and differentiation with these. The piezo idea is good, I wonder if it will be sensitive enough.

Cheers

Greg

Alan Adrian wrote:

One man says 'cheap' at $100, another says 'dear' at $5. The silicon integrated sensors are naturally worth a look.

Brian W

I think you can get 2- or 3-axis sensors for that kinda money

Brian W

It's no trick to get _some_ kind of signal out of a piezo device. If you want to get a signal that's repeatable, you need a charge amplifier to buffer its output. Commercial ones tend to be pricey.

-Mike-

Analog Devices has them for a "cheap" price ($8-$25 from digikey), with either pwm or analog output. Can integrate directly to microcontroller. Crossbow makes some nice eval boards with firmware listings available. I got one based on ADXL202 (2-axis) for about $40 a couple of years ago. Came with windows app as well.

In article , Mike Halloran writes

There can be confusion about accelerometers. Piezo Charge generating are AC coupled and have to be integrated to give quasi DC coupling. Resistive and magnetic/electrostatic servo are DC coupled and the limitation is drift with time. The AD accelerometers are electrostatic servo DC coupled but with significant drift.