Accelerator meter
Accelerator meters are very exciting little things. When I say "little", I mean it, as they usuallyfits 4 or more on a finger nail! And each typically has some 7-20 points so solder. This makes them quite hard to work with, and so I recomend that you also buy a board of some sort, so that you end up with something that you can hook up to your Microcontroller easily.
What you get from the thing is a signal. The signal can be analouge, I2C, or anything else, depending on the thing you get.
I prefer analouge, it is just SO easy to work with; hook it up to an analoge input, read, you are go :)
So what does it return to your microcontrolelr, then?
Well, inside the tiny box is a liiitle chamber with a gas or something. And around this gas cloud or whatever, there are sensors. The gas is lighter or heavier than air or something (this is very precise info, no? ;) - and the resoult is that you get info about how the thing is tilted, or moved around in the air.
You can get them with 1, 2, or 3 axis, I have not seen them with 4 yet (joke).
You know them from the Ninendo Wii handles, and you can use them for such things as:
- Balance
- Registering drift on fast robots
- Registering if the robot-pet-animal is lifted up, perhaps shaken by the stupid kid
- Cool "In Air" joysticks
- To build something that will tell you how fast your car is accelerating.. or your bike ;)
- Registering if your Sumo-robot is just getting hit by another
- Making auto-corecting flying things
- and much more :)


More Accelerometers
Practical, readily obtainable accelerometers are teh ST range of micro-machined range. Here's teh 3-axis 6g version:
http://www.st.com/stonline/stappl/productcatalog/app?path=/pages/stcom/P...
ST are more than happy to send you
freebies"engineering samples" of these little twinkies. They're dead easy to use: you just hook 'em up to an analog input.AND you don't have to worry about gasses and clouds and litte chambers. These work by having a little micro-machined springboard (like a diving board inthe swimming pool) in, which produces a voltage when it is deflected. This voltage is amplified and sent out to your microcontroller's ADC.
One pain about them: they are CMOS and as such prefer a 3.3V supply when we seem to mostly work off 5V.
God created the integers; all else is the work of man - Leopold Kronecker
More II
These:
http://search.analog.com/search/default.aspx?query=accelerometer&local=e...
used to be my favourites and if anyone can find a source for them, please let me know. I'd love a couple more of teh 10g PWM versions. Rather than an analog signal, they output a PWM rather like the one used to position a servo motor. AND they are happier to run off 5V!
God created the integers; all else is the work of man - Leopold Kronecker