Tinyduino motion logger

[jpencausse]

Hi,

Following this question:
http://forum.tiny-circuits.com/index.php?topic=273.0

I would like to create a little device that log accelerometer motions for 2 weeks on battery. So
- Tiny Accelerometer
- Tiny Duino
- Tiny Battery
- Tiny SDCard ?

The idea is to do something like motion cookies from sen.se  (https://sen.se/store/cookie/)

But I don't know
- if it is possible and how to handle the battery ?
- if i have to add something to keep track of the timestamp (because 3 shield is already big object)

Did someone already do that ?

[Grimstone]

If you are looking to create a motion data logger, it sounds like you have the right idea. You will need a SD card shield. The storage on a TinyDuino is too limited for two weeks worth of data. You would need to set the time/date at the sketch upload point to use for a timestamp. Otherwise, you will need a real time clock shield as well which will draw more current. The TinyDuino would then pull the accelerometer data at the time interval you desire, calculate the current time based on the start time plus number of intervals, and write it to the SD card.

I would use the TinyDuino with LiPo support for the LiPo battery tends to last alot longer than the coin cells.

It sounds like a great little project. If you want to take it a step farther, you could use the 9dof shield and get compass direction and gyro orientation as well which would be cool if you expect the item to be rotated a great deal during application.

Have fun.

[jpencausse]

Thanks Grimstone,

Logging seems to be easy, I already did some test flashing the tinyscreen to red, etc ...

But I'm very afraid with battery that might not last so long. And I don't know how to set sleep mode (While sleeping it do not take an accelerometer value)

And the size, sen.se cookies are small ! Even if it is DIY adding shields will enlarge the object

[Ben Rose]

Unfortunately if you want an accurate timestamp you'll need to add the RTC board or a bigger battery- the processor needs to keep in at least idle mode to keep time, which uses something like 3mA, quite a bit over 2 weeks.

You might be able to get away with writing to the internal flash if you only need 8 bit values every few minutes, or only log actual movment, or something like that.

[jpencausse]

Thanks Ben Rose,

Well, I only need to write :
2015.06.19_16:05:02
2015.06.19_16:05:12
2015.06.19_16:07:02
2015.06.19_16:09:02

Let's say a motion is an acceleration with an amount greater than a given threashold. I could look at x,y,z every 200ms.

Many Fitness tracker works for +6 month but I know design of Arduino (and now Tinyduino) are not well suits for long battery.