This battery powered strain indicator interfaces with strain gauges in different settings (single linear, rosette) to obtain strain along a single orientation or to obtain principle strain axes using a rosette. I'm using OMEGA Engineering 0°/45°/90° Planar Rosettes.
The project is based on a Wheatstone bridge to obtain readings from strain gauges.
The goal of this project is to demonstrate practical strain measurements to Civil Engineering students at Alexandria University during their Structural Analysis Lab and Materials Lab.
Strain Gauge Planar Rosette: 3 mm 0°/45°/90° grid, 120 Ω, 2-leads, 1 m long
32 bit ARM processor
Color 320x240 TFT Display
Data Converters / Analog to Digital Converter ICs (ADCs)
I tested the strain indicator unit with a rosette, next step would be calibrating the readings with a commercial strain indicator at college.
The readings shown on display are just the raw voltage from the Wheatstone bridges in milli-Volts, Later I'll add the rosette as well as the linear gauges equations to calculate strain using these readings, GF (gauge factor or sensitivity) which is dependant on gauge material/type and finally the orientation and bridge configuration (Full-Bridge / Quarter-Bridge).
In my case all the channels are quarter bridges with 120 Ohm SMD resistors.
I just finished soldering all of the components to the PCB and I found out I missed a track from Teensy's VIN to the VCC of the display and all I got was the backlight LED, after a little troubleshooting with the multimeter continuity mode and reviewing my designs I added a wire (the yellow one in the photos below) going from VCC to VIN and it worked!
Btw this is my 1st try with a hot air soldering station and it went great, I used it to solder the 120 Ohm SMD resistors on the board. The rest of the components were soldered using a normal iron.