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I currently have an ADXL345 accelerometer.

For a project, I need to be able to detect if my device has a heavy collision with a wall / hard surface. I need to trigger other events on a big collision. Which accelerometer with a range up to 200G would be the best? ADXL193? I'm using an Arduino Uno, so i'd prefer if it could easily be integrated with existing library/ code.

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  • \$\begingroup\$ Do you really need 200G? Do you need all the accelerometer info, or just to ID a big collision? \$\endgroup\$ – Scott Seidman May 28 '13 at 12:28
  • \$\begingroup\$ Why do you need an accelerometer? You can have "bumpers" and maybe tell how hard it is (apply something that will absorb soft blows-maybe a thin layer of sponge), which will be easier. \$\endgroup\$ – Anonymous Penguin May 29 '13 at 0:56
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TL;DR:

An accelerometer may be overkill for impact sensing, besides the constant data reading and processing overhead. Use an inexpensive impact switch or vibration switch instead.


Out of curiosity, tried the following:

  • Opened up a cheap pedometer that came free with something. Pedometer

  • Unsoldered the little vibration switch inside, that rattles when one walks. These are tilt / vibration switches, pretty inexpensive (~ $2.45 for 10, free shipping, on eBay): Vibration switch

  • Cut a hole into a foam "stress ball" toy, just enough to fit the little switch, a CR2032 coin cell, and an Arduino Nano inside it.
  • Wired up the switch between pin 2 and GND on an Arduino Nano clone to capture the switching
  • Set up a sketch for a RISING interrupt 0 on Pin 2, setting internal pull-up on. That way, the switch going from open to closed triggers the interrupt code (which debounces the interrupt and toggles an LED)

Now, I get an LED lighting up if the ball is thrown hard against the wall, but not if the ball is merely dropped from table height. Basically the foam softens the impact enough for it to be sensed only if it hard enough. This "hard enough" would depend on the application and the buffer material used.


Of course, the above is not a recommended production or design mechanism. It is an analogue to a properly rated impact switch, such as the Select Controls 3123-2-000 impact switch, rated for 50-200 G impact sensing.

There are other such inexpensive spring-based impact switches available, for omnidirectional, planar or axial (unidirectional) impact sensing, and trigger thresholds from 0.5 G through to 500 or more Gs. Pick one that suits your specific requirement and budget.

The microcontroller control method would remain as in the experiment above: An edge trigger interrupt on the switch output, to do whatever the desired impact sensing outcome needs to be.

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It's always hard to know what is 'best' but after a quick read of the ADXL193 datasheet and some observations:

  • Supply voltage is 5V so a good match with 5V Arduino systems
  • It's available in a +/- 250g range which meets your requirements
  • Output swing is 0.25V to 4.75V which is a good range for a 5V ADC input
  • Analog Devices is a very reputable manufacturer and pricing looks reasonable

So I can't see a reason not to go with that part. Depending on your exact requirements you'd just have to write some code that continually takes ADC readings and trigger an event when a preset level is exceeded. Either that or take a look at a comparator that triggers when a certain threshold is exceeded.

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  • \$\begingroup\$ Essentially, all I am wanting to do is ID a big collision \$\endgroup\$ – Jamal May 28 '13 at 12:31
  • \$\begingroup\$ @Jamal, it looks like a good solution to me. Vehicle collision is listed as a suggested application. There might be other ways such as improvising a way to dampen a switch with a spring but one advantage to an accelerometer is that you'll be able to easily take in measurements and fine-tune the threshold. \$\endgroup\$ – PeterJ May 28 '13 at 12:39
  • \$\begingroup\$ Should it matter much that it is single axis and not three axis? \$\endgroup\$ – Jamal May 28 '13 at 12:57
  • \$\begingroup\$ @Jamal, that really depends on how you expect the impact to occur. If largely 'head on' because say it's a vehicle driven into a wall then no because the main impact will be along one axis. If you expect side impacts then you'd likely need a second one mounted at 90 degrees to the other. \$\endgroup\$ – PeterJ May 28 '13 at 13:01

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