First Light

A project log for Rock Squeezing

A demonstration of rocks as springs.

John LeemanJohn Leeman 08/29/2015 at 12:210 Comments

Today I hooked up an old granite cube that is about 5 cm on a side with 4 strain gauges to the HX711 board. I modified the example sketches to just output the raw ADC readings (since I am not trying to weigh something right now). I squeezed the rock as hard as I could 4 times and recorded the data at about 4Hz. Graph below.

I did notice that when I moved the cube around, the DC offset of the signal would change, but that's because it has a 1.5+ meter long cable with no shielding. I think I'll build another block with 8 strain gauges (to double the sensitivity) and a shorter cable. I think I'll just have 4 binding posts on the case to connect any block/load cell. Should also have knobs for DC offset and scale unless I can think of ways to have the Arduino cleverly scale the graph that will be displayed on the LCD.