The ADXL345 is a tiny and low power 3-axis accelerometer with a resolution of 13-bit measurement at up to ±16 g. Digital output data can be accessed by either an SPI (3- or 4-wire) or I2C digital interface. ADXL345 is used in the headset and sensitive devices like medical and industrial automation as it measures the static acceleration of gravity in tilt-sensing applications and dynamic acceleration. The resolution of ADXL345 is 3.9 mg/LSB that enables measurement of inclination changes less than 1.0°.
ADXL345 3 axis accelerometer
There are special sensing functions:
- Activity and inactivity sensing detect the presence or lack of motion and if the acceleration on any axis exceeds a user-set level.
- Tap sensing detects single and double taps.
- Free-fall sensing detects if the device is falling.
These sensing functions can be mapped to one of two interrupt output pins (INT1 & INT2). Low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation. The ADXL345 is supplied in a small thin plastic package.
Working
The sensor consists of a micro machine’s structure on a silicon wafer. Polysilicon springs suspend the structure, which allows it to deflect smoothly in any direction when subject to acceleration in the X, Y and/or Z-axis. Deflection causes disturbance (change) in capacitance between fixed plates and plates attached to the suspended structure. This change in capacitance on each axis is converted to an output voltage, which is proportional to the acceleration on that axis. Phase-sensitive demodulation is used to determine the magnitude and polarity of the acceleration.
Features ADXL345:
- It can be operated with 3.3V/5V supply of microcontrollers.
- Low power, small & easy to install.
- Supports I2C and SPI interfaces.
- 3-axis measurement can be used to measure static and dynamic acceleration.
- 4 sensitivity ranges from +/- 2G to +/- 16G and it supports output data rates ranging from 10Hz to 3200Hz.
Pin Description:
The board has 08 pins with the following functions:
| PIN | Description |
| VCC | Supply Voltage. |
| GND | Ground. |
| CS | Chip Select. |
| INT1 | Interrupt 1 output. |
| INT2 | Interrupt 2 output. |
| SDO | Serial Data Output / I2C Address Select. |
| SDA | Serial Data Output / I2C Serial. |
| SCL | Serial Communication Clock. |
Specifications:
- Operating Voltage: 3.3 – 5 volts.
- Small dimension: 3 mm × 5 mm × 1 mm LGA package.
- 10,000 g shock survival.
- Free-fall detection.
- Tap sensing.
- Activity & inactivity monitoring.
- User-selectable resolution.
- Full resolution, where resolution increases with g range, up to 13-bit resolution at ±16 g.
- SPI (3- and 4-wire) and I2C digital interfaces.
- Power consumption scales automatically with bandwidth.
Applications & Uses:
- Mobile phone and sensitive devices.
- Medical and industrial instrumentation.
- It can be used in gaming devices.
- Personal navigation devices.
- HDD protection (Hard disk drive).
