Final presentation
Introduction
We started the study of sensor technology with Accelerometer closely packed in case from Murata. The first challenge was to open that without breaking the internal electronic part/circuit. After different type of force experiment on box, the small PCB come out. After close look, Accelerometer and relevant components. Then start searching for more sensor related to Accelerometer and find XTrinsic FXLN83xxQ from Freescale.
Typical applications
XTrinsic FXLN83xxQ accelerometers are used for
Applications in industrial
Medical
Tamper detection
White goods: tilt, vibration, and shake detection
Motion sensing in robotics applications
Inclinometer, vibrometer
Activity monitoring in sports and medical device
Physical principles
Xtrinsic FXLN83xxQ 3-Axis Low- Power Analog-Output Accelerometer FXLN83xxQ is a family of 3-axis, low-power, low- g , analog output accelerometers that consist of an acceleration sensor along with a CMOS signal conditioning and control ASIC in a 3x3x1mm QFN package. The analog outputs for the X, Y, and Z axes are internally compensated for zero- g offset and sensitivity, and then buffered to the output pads. The outputs have a fixed zero- g offset of 0.75V, irrespective of the VDD supply voltage. The bandwidth of the output signal for each axis may be independently adjusted using external capacitors. The host can place the FXLN83xxQ into a low-current shutdown mode to conserve power.
Characteristics
Supply voltage (V DD ) from 1.71 V to 3.6 V
Accelerometer operating ranges selectable
±2 g or ±8 g (FXLN83x1Q)
±4 g or ±16 g (FXLN83x2Q)
Low current consumption of 180 μA (typical)
Output Bandwidth Options
High bandwidth, 2.7 kHz (XY axes), 600 Hz (Z axis), (FXLN837XQ)
Low bandwidth, 1.1 kHz (XY axes), 600 Hz (Z axis), (FXLN836XQ)
3 x 3 x 1 mm, 12-pin QFN package (0.65 mm lead pitch)
Robust design with high shock survivability (10,000 g )
Operating temperature from –40 °C to +105 °C
MSL 1 compliant
Interface electronics
The following recommendations are a guide to an effective PCB layout:
- The PCB land should be designed with Non-Solder Mask Defined.
- Signal traces connected to pads should be as symmetric as possible. Dummy traces must be put on the NC pads in order to have same length of exposed trace for all pads.
- No copper traces should be on the top layer of the PCB under the package. This will cause planarity issues with board mount.
Printed Circuit Board Layout and Device Mounting:
Soldering Considerations:
• Stencil thickness should be 100 or 125 μm.
• The PCB should be rated for the multiple lead-free reflow condition with a maximum 260 °C temperature.
• A standard pick-and-place process and equipment shall be used. A Hand soldering process is not recommended.
• A screw-down or stacking to mount the PCB into an enclosure must not be used. These methods could bend the PCB, which would put stress on the package.
Materials
Silicon
Silicon is the material used to create most integrated circuits used in consumer electronics in the modern industry. The economies of scale, ready availability of cheap high-quality materials and ability to incorporate electronic functionality make silicon attractive for a wide variety of MEMS applications. Silicon also has significant advantages engendered through its material properties. In single crystal form, silicon is an almost perfect Hookean material, meaning that when it is flexed there is virtually no hysteresis and hence almost no energy dissipation. As well as making for highly repeatable motion, this also makes silicon very reliable as it suffers very little fatigue and can have service lifetimes in the range of billions to trillions of cycles without breaking.
Polymers
Polymers can be produced in huge volumes, with a great variety of material characteristics. MEMS devices can be made from polymers by processes such as injection molding, embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing cartridges.
Metals
Metals can also be used to create MEMS elements. While metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by electroplating, evaporation, and sputtering processes. Commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver.
Ceramics
The nitrides of silicon, aluminium and titanium as well as silicon carbide and other ceramics are increasingly applied in MEMS fabrication due to advantageous combinations of material properties. AlN crystallizes in the wurtzite structure and thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. TiN, on the other hand, exhibits a high electrical conductivity and large elastic modulus allowing to realize electrostatic MEMS actuation schemes with ultra thin membranes. Moreover, the high resistance of TiN against bio corrosion qualifies the material for applications in biogenic environments and in biosensors.
References
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FXLN83xxQ
Datasheet available online under below link. (http://cache.freescale.com/files/sensors/doc/data_sheet/FXLN83xxQ.pdf)
https://www.novapublishers.com/catalog/product_info.php?products_id=42805
For Programming (https://www.safaribooksonline.com/library/view/basic-sensors-in/9781449309480/ch04.html)