What are Accelerometers?

Accelerometers are electromechanical devices that measure acceleration, the rate of change in velocity of an object. It uses axis-based motion sensing, as a way of detection. In this blog, I’ll be recommending the ADXL335 and ADXL356C accelerometers with a quick assessment on each through my buying guide.

Before that, Have you wondered?

Have you wondered the following:

  • How does your phone accurately display which direction you’re pointing at when using a compass/maps app?
  • How does your car detect when it’s needed to deploy an airbag?

It is indeed done through an accelerator and it’s axis-based motion sensing.

What are accelerometers used for?

Apart from axis-based motion sensing, it can be applied in other various scenarios including:

  • Earthquake detection
  • Medical devices
  • Speed/movement of an object
  • Motion sensor games/applications

Accelerometer Buying Guide

To select a suitable accelerometer, one should consider the following components:

Components Recommendations/Considerations
Range For precise readings:
Pick a smaller full-scale range as it’ll give you a more precise reading due to a more sensitive output

Consider acceleration ranges that fit your projects.
Interface Easiest interface to work with:
Analog interface, as analog-to-digital converters (ADCs) are implemented in most microcontrollers

For producing fixed frequency:
PWM interface, produces a square wave with fixed frequency but duty cycle of the pulse varies with sensed acceleration

Most features and lesser noise:
Digital interface, features either SPI or I²C serial interface but may be difficult to integrate with microcontroller
Axes Three-axis accelerometers, most common and not significantly more costly as compared to one or two axis accelerometers
Power Usage Required current consumption of an accelerometer is usually in the 100s of µA range
Take into consideration required power.
Bonus Features Picking newer models of accelerometers may be a better choice as they include more bonus features such as:
Selectable measurement ranges
Sleep Control
0-g detection
Tap sensing

Recommended Accelerometers

Based on the components from the previous table, the following 2 Accelerometers are my recommendations that you can take into consideration.

High precision and affordable accelerometer: Grove – 3-Axis Analog Accelerometer (ADXL335)


The Grove – 3-Axis Analog Accelerometer (ADXL335) is small size, low power, complete 3-axis accelerometer with signal conditioned voltage outputs. This analog accelerometer is a low g accelerometer with a minimum full-scale range of ±3 g.

Assessment:

  • Range: ±3g, small range with precise readings
  • Interface: Analog, easiest interface to work with
  • Axes: 3
  • Power consumption: 350μA at 3V (typical)
  • Bonus features: No bonus features

Applications:

  • Motion Sensor
  • Shock detector
  • Vibration sensor
  • Toy car
  • Robotics

Although there are no bonus features, it’s still a solid pick up option due to its affordability, functionality and fulfilment of other criterias.

Premium/High-end option: Grove – 3-Axis Analog Accelerometer ±40g (ADXL356C)

If you’re looking for the high-end, industrial-grade accelerometer, the ADXL356C is the one for you.

Assessment:

  • Range: ±10g – ±40g, only a little calibration work is needed to get a relatively accurate result
  • Interface: Analog, easiest interface to work with
  • Axes: 3
  • Power consumption: Ultra-low,
    Normal operation mode-150 μA, Standby mode 21 μA
  • Bonus Features:
    • Low, drift, low noise; ideal for wireless condition monitoring
    • Hermetic package that offers excellent long-term stability 0g offset vs. temperature (all axes): 0.75 mg/°C maximum

Applications:

  • Inertial measurement units (IMUs)/altitude and heading reference systems (AHRSs)
  • Platform stabilization systems
  • Condition monitoring
  • Seismic imaging
  • Tilt sensing
  • Robotics

The ADXL356C is a high-performance accelerometer that not only check the boxes that you want from an accelerometer but offers a wide range of applications as well.

Pairing the recommended accelerometers

Seeeduino Lotus Cortex-M0+

The Seeeduino Lotus Cortex-M0+ supports the above-recommended accelerators with its availability of 14 digital input/outputs (10 of which support PWM) and 6 analog input/outputs.

Other product features include:

  • Compatibility with Arduino UNO
  • ARM® Cortex®-M0+ 32bit 48MHz microcontroller(SAMD21)
  • 12 on-board Grove connectors
  • Support Power Path Management
  • Support micro-USB or Li-Po battery powered
  • 2A maximum charging current
  • Suitable for low power design

Summary

All in all, accelerometers are commonly seen in many day to day applications and can be utilized for many fun and interesting projects. Consider picking up one today!

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