Jump to content

9 posts in this topic

Posted

So I made a DIY cell phone mount for my bike, and someone mentioned that their phone broke after using a bike handlebar mount for a long bike trip.  Apparently tiny sensitive solder joints don't like to feel the impact of every sidewalk curb, railroad track, and tree root my bike hits.  So I decided to record the accelerometer data for a quick 4 minute ride, and it looks pretty high, but I don't actually know how high that is.  Acceleration values mean nothing to me.  But I can tell you that those green ones are peaking at around 20,000m/s2, and the green is the X axis, and that was the axis perpendicular to the ground (ie every time the phone went up and down).  The forward/backward/left/right axes didn't feel anywhere near as much force.  Does that mean my phone was experiencing over 2,000 G's of force (1G = 9.8m/s2) every time I hit one of those big bumps?  Is that something to worry about?
 
Is there anyone here with some experience in stress testing electronics that could tell me how long my phone would last if it experiences these kinds of impacts?
 
(note, the graph's y-axis is on a logarithmic scale)
 
en2w.png
 

Share this post


Link to post
Share on other sites

Posted

So I went for another 7 minute ride, this time with a 1" thick chunk of some good memory foam, placed as padding between the phone and the handlebars, and while the logarithmic graph may not show much difference, the maximum force the phone experienced was more than 50% smaller than having no padding at all, so it's an improvement.
 
[URL="http://imageshack.us/a/img546/7564/1o1r.png"]l9dg.png[/URL]

Share this post


Link to post
Share on other sites

Posted

Definitely not 2000 G's anyway. And it probably won't make much of a difference on your phone unless you do downhill offroad biking

Share this post


Link to post
Share on other sites

Posted

Cannot be nearly that much. It's insane.

 

Frankly, I don't think those accelerometers in phones and such are even designed and capable for more than detecting a presence and a rough estimate of motion vectors.

 

I will talk out of my ass now, but some distant grasps of logic might be involved and even appear.

 

First, you need to find the value range, sample rate and sensitivity (accuracy) of your device's accelerometer. Many system tools can do that, but values will be less in practice.

 

Because *no* accelerometer (that simple and small) can even measure such a large range of values. Consider that 2000 g is 19.6 km/s2. Registering a small bump lasting 1 millisecond would need to have thrown the device about 20 meters in one direction or another. That, obviously, didn't happen. In fact, it's an insane value - if we reduce time of that impact to 10

Share this post


Link to post
Share on other sites

Posted

You didnt say what your using the phone for but if your going off road your better off with an arm pouch if you must carry it, this will at least remove all the severe jarring impact

Share this post


Link to post
Share on other sites

Posted

You didnt say what your using the phone for but if your going off road your better off with an arm pouch if you must carry it, this will at least remove all the severe jarring impact

 

This x1000. My iPhone 5 goes in my bag when I'm mountain biking, on my back. It has never had an issue, and I've even gone over the bars and and landed on it. 

Strapping it straight to some metal handlebars, on the other hand, would probably beat it to death right quick. I killed an iPhone 3G by accidentally bouncing it off the edge of a table, that's the sort of impact phones really do not like.

Share this post


Link to post
Share on other sites

Posted

Cannot be nearly that much. It's insane.

 

Frankly, I don't think those accelerometers in phones and such are even designed and capable for more than detecting a presence and a rough estimate of motion vectors.

 

I will talk out of my ass now, but some distant grasps of logic might be involved and even appear.

 

First, you need to find the value range, sample rate and sensitivity (accuracy) of your device's accelerometer. Many system tools can do that, but values will be less in practice.

 

Because *no* accelerometer (that simple and small) can even measure such a large range of values. Consider that 2000 g is 19.6 km/s2. Registering a small bump lasting 1 millisecond would need to have thrown the device about 20 meters in one direction or another. That, obviously, didn't happen. In fact, it's an insane value - if we reduce time of that impact to 10

Share this post


Link to post
Share on other sites

Posted

Maybe the frequency between reads [sample rate] is a lot faster or the software is calibrated to a lesser quality on one compared with the other.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0

  • Recently Browsing   0 members

    No registered users viewing this page.