Accelerometer project preliminary questions

Hello folks!

A bit of background - I have a small amount of microcontroller experience (built an autonomous robot for a competition), and a reasonable amount of coding experience.

The project I'm attempting is related to rock climbing. I'd like to attach a controller/accelerometer/logger to my climbing harness to record things like biggest fall, biggest shock experienced, total distance climbed, etc. But before I purchase a bunch of parts, I'm looking for a sanity check and some suggestions!

The accelerometer I'm leaning towards is this guy: SparkFun Triple Axis Accelerometer Breakout - ADXL345 - SEN-09836 - SparkFun Electronics

Besides the up to +/- 16g capability, some of its other features look especially useful for conserving battery life, etc (talking about the free fall detection, in/activity sensing, interrupt output pins, etc.).

Question 1: Does this appear to be a solid choice for the application I've described? Is it missing something that I might want, or is it overkill? Have I proven my ignorance with this horrible selection?

Moving on...the next thing I'm wondering about is data capture. Storing the data on microSD seems an appropriate option, especially considering I'll just be storing lines of text.

Question 2: Is microSD the best choice here? I'm not sure what options there are beyond storing on dedicated flash memory like this, but I don't want to make too many assumptions.

Question 3: What do I gain (beyond the obvious) by using a discrete data logger such as this: SparkFun OpenLog - DEV-13712 - SparkFun Electronics ? Would that simplify the design by possibly obviating the need for a separate microcontroller (Arduino Uno is what I have at the moment) to make everything work? Or would I still need a controller beyond the one included on that data logger unit? What are the implications of getting just a microSD card breakout board like this SparkFun microSD Transflash Breakout - BOB-00544 - SparkFun Electronics instead, and handling all of the logging with the Uno I'm already planning to use (which I may switch to a mini or something down the line)?

Sorry if these questions are too broad, I've tried to organize and provide the necessary information so that they can be addressed. Please let me know if there's something I've left out, as I'm a little sleepy!

Thanks for your help!!

benjamintheyon:
Question 3: What do I gain (beyond the obvious) by using a discrete data logger such as this: SparkFun OpenLog - DEV-13712 - SparkFun Electronics ? Would that simplify the design by possibly obviating the need for a separate microcontroller

As I read the datasheets, the accelerometer uses I2C/SPI which the data logger doesn't handle. So you would still need the processor.

They seem to have basically packaged up an SD card chip on a board, so you could get a similar thing by just wiring up an SD card yourself (and then you can just pull the card out and plug it into your computer to get the data off).

For simplicity, an SD card shield might be easiest. I think some come with a bit of prototyping space, so you could solder the accelerometer onto it. eg.

That gives you the clock, the SD card, and room to solder on the accelerometer.

Mind you, in your shoes I would be a bit worried about the shield coming adrift if you are subjecting it to multi-G shocks. But perhaps a bit of PVC tape wrapped around the whole thing would secure it.

Thanks very much!

I don't have any experience with I2C/SPI, so that should be fun. I like your suggestion, however, the accelerometers I'm looking at appear to be SMD,which is why I favored the breakout board. Also, the shield you linked claims not to be compatible with MEGA, which I believe would preclude the Uno I already own?

I don't mean to sound ungrateful, just trying to be careful here. Should I look for a dedicated datalogger, or just wire up an SD card as you've said?

Thanks!
Ben

benjamintheyon:
Also, the shield you linked claims not to be compatible with MEGA, which I believe would preclude the Uno I already own?

I'm not sure what you mean by that. The shield IS compatible with a Uno, but not a Mega.

The Arduino Uno uses an Atmega328 chip but it isn't a "Mega". That refers to the Mega2560 board. That has a lot more pins.

I don't have any experience with I2C/SPI, so that should be fun.

Thanks, that's exactly what had me held up (Atmega vs Mega board).

And these links look extremely informative! I'm gonna purchase the accelerometer breakout and the SD card one as well.

Thanks so much for your help, it's great to get immediate help from the community like this!