Rustic Engineering

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Archive for May 2008

Accelerometers and MEMs technology

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Actually more and more device’s with direction, move or orientation sensing rising in market. This revolution is done by the fact that the price of a type of sensor, the accelerometer, suffer o down in later years. With this, the new sensor comes to the old stuff, aggregating more functions. Products like Iphone and Nokia N95 have accelerometers embedded. Notebook’s, for hard-drive shock protection, are another example. Even the Wii Remote have one… God! I need a accelerometer!!

Well, maybe the true reason is that the technology of MEMS’s is growing up. MEMS – Micro-Electro-Mechanical Systems – is the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate, through microfabrication technology. And when i say microfabrication, stand for really microfabrication! See…

MEMS - Micro-Electro-Mechanical Systems

Accelerometers technology is made by this kind of technology. You can find more and more information in Analog Devices website. They have a great family of ADXL named devices that are great 2 or 3 axis MEMS accelerometers in a small encapsulation like LCC (Terminal Ceramic Leadless Chip Carrier), LFCSP (Leadframe Chip Scale Package or other “evil-made-package”.

LFCSP - Good for hobbie

Thank God (or no) that Sparkfun have made greats breakout boards for accelerometers like ADXL202, ADXL330. With this breakout, you have no difficulties to integrate the accelerometers with your breadboard.

ADXL213 Accelerometers

Some ADXL sensors output Analog, some sensors output both Analog and PWM. The Analog output is a voltage relation with the acceleration perceived by sensor. PWM outputs, have a Duty Cycle length relation. In any case, a Microcontroller with ADC for analog, or a counter (for PWM) is a solution easy to integrate. PWM can be easier because don’t need ADC capabilities, and any simple Microcontroller can be used. Reading voltage, getting acceleration. Start a counter, reading the value and getting the acceleration. So easy…

Now, is time to test a accelerometer. Above, I’m listing some common types and your characteristics

  • ADXL213 +/-1.2g, 2-Axis, High precision PWM and Analog;
  • ADXL203 +/-1.5g, 2-Axis, High precision Analog;
  • ADXL202 +/-2g, 2-Axis, PWM and Analog;
  • ADXL311 +/-2g, 2-Axis, Analog;
  • ADXL210 +/-10g, 2-Axis, PWM and Analog;
  • ADXL330 +/-3g, 3-Axis, Analog;

I’m have the ADXL213 and ADXL330 in a friendly 0.1″ pins breakout board. The ADXL330 are extremely low noise and low power consumption (only 320uA!!!).

My intention with this post is start a study about the use of accelerations, with simple circuits and more explanations. In the next post I’m show my first test circuit. Thanks.

Written by forrequi

May 27, 2008 at 16:41

Posted in electronic

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PIC and RFiD

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I’m working in the last days in a RFID device. This is a great technology for security and i’m planning to use this device in my house’s door. The code still have some bug’s, but the core (reading the ID from any RFiD card) is woking.

PIC and RFiD

Written by forrequi

May 1, 2008 at 15:38

Posted in electronic

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