Accelerometers-project 4
From Physical Programming
Accelerometers elliot henkel
Accelerometers are used to measure proper acceleration. They accomplish this by a small mechanical mass mounted in a shell or casing that is connected to a spring. As the spring moves inside the cases it compresses or stretches the spring. This movement is then measured by a piezoelectric, piezoresistive, or capacitive device which converts the mechanical movement of the mass inside the cases into an electrical signal.
Proper acceleration is the ability of the mass, the casing and the spring to act in a way similar to a person in a lift. Imagine standing in a lift (elevator) and going down. When you stop you feel yourself press against the floor. In this case you are the mass, the lift the case. Now put the spring into the equation. You are standing on a board with a spring between you and the floor, almost in thin air. The mass of you holding the spring at a position where you have compressed what your weight will on the spring. Then as the lift begins to go down you slowly compress the spring a bit more. When you are stopping the spring compresses further. The person next to you (the piezoelectric converter) then measures the amount the spring is compressed and converts that measurement into your acceleration, which could be measured in m/s^2 (metres per second), cgs (centimetre per second) or g (g-force). The person then sends this information to somewhere for it to be processed and documented or in our case used to control a reaction.
Accelerometers are used in many different applications such as measuring a cars acceleration, for measurements like 0-100 km, and 100-0 km, which are highly accurate, measuring seismic activity accurately, in hard drives, accelerometers are used to detect dropping, when the drive is dropped and reaches a pre determined rate of acceleration the drive turns itself off to prevent loss of data, heavy machinery uses accelerometers to determine faults which could be harmful to workers and many personal electronic devices such as the iPhone, Wii and PlayStation 3 remote.
There a many different forms of accelerometers depending on the axis’s they detect acceleration on. They exist from one to six axes. A pedometer could use a one-axis accelerometer, as it only needs to measure the movement up and down to register its step count. However a Nike product used to measure steps, distance covered, pace, time and calories burned, uses a 3-axis accelerometer. The new PlayStation 3 uses a 6-axis accelerometer in its controllers, which attempts to simulate a real driving experience by steering completely by movement.
I intend to use a 2 axis accelerometer. This can be incorporated with the arduino and a breadboard easily. The memsic 2125 is a dual axis accelerometer. The mid left output is the y axis and the mid right output is the x axis. If you positioned the x axis parallel to the width of the body and the y axis vertically they could control RGD LED lights colour using the arduino program. The two bottom outputs are the power. This accelerometer works differently to a spring mounted mass accelerometer. It has a bubble that when the device is moved, the piezoelectric sensor detects.
The T output can be used to detect temperature, but needs an external converter to transfer the analogue signal to a digital one.
I would like to incorporate an accelerometer in my final project incorporating LED lights that change colour depending on the pace of the user, which would inturn show their mood through the speed of their motion.
http://en.wikipedia.org/wiki/Accelerometers
