Accelerometer Sleep Data

The holidays and a new baby in the house can really cut into a guy's free time! I've been making some progress though...

I've proven out just about every sub-system I'll need to build my bruxism monitor and alarm (code-named, chompr). This includes the power supply, microcontroller, Muscle Sensor, OLED display, additional SRAM, accelerometer and microSD card. Here's what the circuit looks like on a breadboard (or two!)

Before I solder everything down to a protoboard, I want to do a little more characterization of the Muscle Sensor circuit. This piece is going to be critical to the success or failure of the project. The EMG signals produces by temporalis muscles are very small (microvolts). Detecting these signals and differentiating them from electrical noise will be difficult, especially if the amplifier circuit isn't designed correctly.

In the meantime, I've decided to build a separate accelerometer circuit to measure my body position while sleeping.  For some time, I've been curious if there is a correlation between my sleep position and bruxism activity. For example, does sleeping on my back cause me to snore or otherwise have my breathing interrupting, triggering me to grind my teeth? My bruxism activity level is not consistent. Some mornings I feel great and others I do not. This device might help to answer some of those questions.

The circuit (code-named, chompr movr) uses a triple axis accelerometer breakout board and microSD card adapter from SparkFun Electronics. It logs raw X, Y, Z accelerometer data, along with a timestamp, every 2 seconds. I prototyped the circuit on a breadboard first, and then soldered everything on to a perforated protoboard.

The accelerometer is tucked under the microSD card, so you can't see it in the photos. I added a removable jumper on the board so I could measure the current consumption. This will give me a better idea of the battery requirements for the final circuit (more on this later).

Here's the whole thing mounted in an Altoids tin.

And again, with the programming cable attached.

My plan is to record some accelerometer data over the next few weeks and see if it correlates to how I feel in the morning. I'll post my findings here.


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