Project will be broken into phases. At the end of which there will be a working prototype that may be further refined for aesthetic reasons (i.e. smaller):
Phase I: Instrumenting a Crank Arm
- DONE Source strain gauges
- DONE Optimize installation of strain gauges onto aluminum crank arm
- DONE Source instrumentation amplifier (SOIC package, single supply) and auxiliary components
- DONE Construct prototype instrumentation amplifier (IN-Amp)
- DONE Perform validation of instrumented crank arm with custom instrumentation using NIST traceable reference (Instron 8872)
- DONE Determine linearity, hysteresis, fatigue life, and sensor crosstalk
- DONE Analysis of the signal will indicate need for filtering (likely need a passive or active LP filter)
- DONE Strain gauge placement that permits linear (or low hysteresis) over desired measurement range
- SEE PHASE II Battery powered instrumentation amplifier that outputs a 0-5 (or 0-3.3)VDC signal
- DONE 10pt calibration is within specification
Phase II: Analog Voltage to LE Bluetooth
- DONE Source and microcontroller with ADC and LE bluetooth module that will allow a minimum sampling frequency of 100Hz (in the Android app).
- DONE Source gyro that will be used to determine rotational velocity of crank arm.
- DONE Determine power requirements of circuit so that an appropriate capacity LiPo battery may be chosen
Phase III: Form and Function
- IN PROGRESS Design custom PCB to integrate all components. No breakout boards (FAILED)...
- NOT STARTED Design custom weather-proof housing
- IN PROGRESS Begin Android application development.
Additionally, grip width is different between snatch and clean so you'd have to re-adjust the gauge (I assume).
There are some training system out there which focus on maximum force/power production, so that'd be a plus. In the snatch, maximum power is typically achieved at less than your max.
Regarding left/right side imbalance: that's typically measured with a force plate under each foot, but measuring at the barbell might just work.
I am wondering if two accelerometers glued to the barbell would just work as well.