Simple Step Tracking Project

A rapid prototype to allow step tracking at foot level. Use case is to validate step tracking algorithms for wrist worn or other biomechanical devices. The device is wore around the ankle. The two main sensors are the force sensitive resistor (FSR) and an accelerometer/gyroscope module. The readings from these sensors are output to an SD card located on the device. Device is powered with a LiPo battery.

Posted by : Tim Truty at Jul 29, 2019

Category : Tech

S.S.T.

Simple Step Tracking

Project overview

Required for project

Hardware

Aims of Project

Goal of the project is to create an accurate step counter.
The raw readings from the sensors are outputted to an SD card
Days of recording in a small footprint to be worn

Usage

Make sure SD card is inserted before power up.
Writes to file DATALOG.txt
If runs out of power last few write timestamps will show incorrect.
Unplug SD to charge
Make sure powered down to reinsert SD
Then reconnect battery

foot1

foot2

Assembly

Fritzing sketch

Bill of Materials: SimpleStepTracking.fzz

Monday, July 29 2019, 16:35:48

Assembly List

Label	Part Type	Properties
J1	Basic Force Sensing Resistor (FSR)	package THT; sensing area diameter .5 "
Part1	Adafruit Feather nRF52	variant variant 1; part # Adafruit #3406
Part2	Adafruit Adalogger FeatherWing	variant variant 1; part # Adafruit #2922
Part3	InvenSense MPU6050	variant MPU-6050; pins 8
R1	220Ω Resistor	tolerance ±5%; package THT; bands 4; pin spacing 400 mil; resistance 220Ω
R2	4.7kΩ Resistor	tolerance ±5%; package 2512 [SMD]; resistance 4.7kΩ
R3	4.7kΩ Resistor	tolerance ±5%; package 2512 [SMD]; resistance 4.7kΩ

Shopping List

Amount	Part Type	Properties
1	Basic Force Sensing Resistor (FSR)	package THT; sensing area diameter .5 "
1	Adafruit Feather nRF52	variant variant 1; part # Adafruit #3406
1	Adafruit Adalogger FeatherWing	variant variant 1; part # Adafruit #2922
1	InvenSense MPU6050	variant MPU-6050; pins 8
1	220Ω Resistor	tolerance ±5%; package THT; bands 4; pin spacing 400 mil; resistance 220Ω
2	4.7kΩ Resistor	tolerance ±5%; package 2512 [SMD]; resistance 4.7kΩ

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Notice correct pull-up resistors on i2c connectiong from mpu module. i2c coms from the mpu6050 is addressed high, module AD0 pin is connect to possitive with a referince in firmware. Voltage divider on FSR.

Output

Unix Times stamp, ax, ay, az, gx, gy, gz, force

1564329544,-816,16584,1672,-214,-350,880,0
1564329544,-648,16960,1540,935,1261,-216,0
1564329544,-832,14980,-168,752,1540,435,0
1564329544,-1304,14308,5164,1640,-1731,1915,0

Current Build

S.S.T