Features
Dynamically selectable full scale: ±250/±500/±2000 dps
SPI, I²C digital interfaces
16-bit data output
Fully configurable low-pass and high-pass embedded digital filters
Programmable interrupt generator
Embedded self test
High shock survivability
Ultra-small 4 x 4 x 1 mm³ LGA package
Benefits
Single sensing structure for motion measurement along the three orthogonal axes eliminates cross-axis interference, with benefits in terms of accuracy and reliability
Embedded digital features fully programmable by the user (integrated low-pass and high-pass filters, selectable full scales and output data rates)
Ultra-small package to address space-constraint applications
I am planning a project in the future that needs to sense movement in 3 dimensions. There are a lot of ways to do it but the easiest I would hope is using an accelerometer sensor. The issue I am having is how sensitive are they ? I need something that can detect movement moving from full stop to next position , with the distance only being a millimeter. I have zero experience with them and this will be my first hobby project using one.
Thinking of a use of these kind of sensors. It reminded of something i would like to build in the future : a 4 rotor UAV helicopter.
A German company has these as an self assembly (meaning you have to assemble it yourself) packet.
Here is a video :
http://www.youtube.com/watch?v=Y4jtguSF0n4&feature=related
And websites :
http://www.microdrones.com/en_home.php
http://www.orbitgis.com/index.php?c=products/microdrone/md_features.htm
a friend of mine actually did that for a controls capstone. the aerospace dept has ongoing research on how to automate that type of flight... so his project was to build the uav and implement their researched automation algorithm. the first part wasnt too hard, but implementing the algorithm was a bit tougher since it had a lot of complex mathematical theory. didnt end up getting the automatic flight work, but he did learn quite a bit.
A little more detail on the project.
It is going to be a controller for people that do not have much movement ability either because of injury or illness. So someone may be able to move their hand or another body part from left to right over a span of 6 inches and cover that distance in about 3 seconds. Or it may be an arm or hand or head. I have looked at other tracking methods like IR but they really don't work well for this specific situation and commercial devices that do exist are made out of one off components that make them really expensive. Really trying to find a way to do something like this on a much lower budget and was thinking if I could attach something like an accelerometer to a foot to track its motion that might work.
I think the gyroscope ic's would definitely work.
But maybe an better and cheaper alternative :
I toyed with an WII mote once, but i was not really happy with the control. I wanted to use a wiimote as replacement for a home theater kind of set up.
But the wiimote gave me instant RSI to get the mouse pointer where i want it.
However, maybe the software on the pc was not all that great. Maybe you can get better precision out of it. The sensor in the wiimote is an : ADXL330
http://www.analog.com/en/sensors/inertial-sensors/adxl330/products/product.html.
Maybe the ADXL327 will work for you. It is more sensitive then the ADXL330.
And it is in a far lower price range(x/10) when compared to the gyroscope ic's.
datasheet ADXL327 :
http://www.analog.com/en/sensors/inertial-sensors/adxl327/products/product.html
The best accelerometer they have appears to beThis is a simple breakout board for the Melexis gyroscope featuring both analog and digital (SPI) interfaces. Designed for dead reckoning navigation applications, the MLX90609-N2 is a 75 degree/s max rate gyro with low drift and programmable bandwidth, this gyro is perfect for digital stabilization and control.
Would the gyroscope or accelerometer be better of these two ?Dual Axis Accelerometer Breakout Board - ADXL213AE +/-1.2g
sku: SEN-00843
Description: Breakout board for the Analog Devices accelerometers in the E8 package. The ADXL is a solid state MEMS accelerometer with digital PWM or Analog output. The ADXL can measure both static and dynamic acceleration. This means the ADXL is suited well for sensing tilt (used in many Glove / Air Mouse applications) and for sensing brute acceleration (rocketry and general motion sensing applications).
A little more detail on the project.
It is going to be a controller for people that do not have much movement ability either because of injury or illness. So someone may be able to move their hand or another body part from left to right over a span of 6 inches and cover that distance in about 3 seconds. Or it may be an arm or hand or head. I have looked at other tracking methods like IR but they really don't work well for this specific situation and commercial devices that do exist are made out of one off components that make them really expensive. Really trying to find a way to do something like this on a much lower budget and was thinking if I could attach something like an accelerometer to a foot to track its motion that might work.
Accelerometers might work for this task - the problem is that a displacement of 1 mm is likely only to generate very small accelerations, for a very short time - this is something that most accelerometers aren't very good at.
E.g. 1mm displacement may result from 20 mg for 100 ms. For a typical MEMS accelerometer, that works out at about 5 units (I call 1 'unit' the amount of acceleration between distinct digital codes) of signal - with a noise of roughly 1 unit rms. Worse, if you are using a 3 axis sensor and adding the signals - you are also adding the noise, so in reality you get about 2 units of noise. Assuming Gaussian noise - that's one false positive every 10 seconds (assuming high low pass filtering to 10 Hz - I'm guessing that this would be as close as possible to the signal band - but you'd probably need to determine this empirically).
Then you've got to consider environmental and physiologic noise. A person's pulse can move a limb by more than 1mm, etc.
I don't see any use for an ARS (MEMS "gyroscopes" aren't actually gyroscopes. Gyroscopes are angular position sensors, whereas a MEMS "gyroscope" is an angular rate sensor). An ARS is not required, and won't help, unless your project requires detection of rotation during acceleration. If you can assume no rotation during acceleration, then an ARS is not required and won't help. Similarly, if you simply want to detect inclination, then an ARS is useless, as all you measure is the derivative, and not the absolute value.
The accelerometer, by contast, will give you the absolute value - and because you can average, you can achieve high precision measurement of inclination - to better than 0.5 degrees with typical MEMS accelerometers. This, in fact, may be a more practical option than trying to detect the acceleration associated with displacement.
Hmm. Just seen your post stating 6" and 3 seconds. Now that is well within a practical detection range, and should work fine.
One common method for determining the tilt or inclination of a system is to integrate the output of a gyroscope. Although this method is straightforward, error associated with null bias stability can quickly compound as the integration period is increased, causing an apparent rotation even when the device is stationary.
In some applications, where the net acceleration or force on a system over time is gravity, an accelerometer can be used to measure the static angle of tilt or inclination. Such applications include gaming, horizon detection in digital cameras, and detecting the heading of a device in industrial and medical applications.
The underlying assumption in inclination sensing with an accelerometer is that the only acceleration stimulus is that associated with gravity. In practice, signal processing can be performed on the signal output to remove high frequency content from the output signal, so some ac acceleration can be tolerated.