Hi! This is my first post ever on a forum, so if you need any info I haven't put here let me know. Also, pardon my english, it's not my first language.
I've been having some issues getting a strain gauge system to function properly. Basically, I was trying to calibrate two strain gauges(120ohms). They were attached on oposite sides of the same end of a metalic tube (so they were right "on top" of each other). I soldered two coper cabels on each SG and connected them on a half bridge using 1% precision resistors of the same resistance (Wheatsone bridge). The corners of the bridge were connected to a HX711 on E+, E-, A+ and A-, that were connected to an arduino mega. Here's a drawing of the schematic, I hope it's visible enough...
Here are some pics of the actual thing. The arduino and protoboard picture is from before I used the precision resistors, so don't mind them, it's just so you can see the connections. Also, I used tiny precision resistors, the camera almost doesn't capture them.
I used precision resistors because at first, using regular 5% ones, I either wouldn't get any data (logs would all be zero) or completely randomic logs that would keep changing line by line without any weight or any type of force being applied to the tube. Once we changed resistors I went back to receiveing no data. I tested with a multimeter for possible short circuits and found none in my soldering, but in fact in the strain gauge's thin metal threads, they were in short circuit with the metal tube. So I resorted to using isolating tape paste on it's metal legs, what got rid of the short circuit according to my multimeter.
But still no luck with getting any data whatsoever. I tested the strain gauges with my multimeter and they seem to work fine, they register light changes of resistance once being strained, but not in my setup! Only ever so often and at completely random moments.
Here's my code:
#include "HX711.h"
// Define HX711 connection pins
#define LOADCELL_DOUT_PIN 50
#define LOADCELL_SCK_PIN 52
HX711 scale;
float calibration_factor = 1.0;
void setup() {
Serial.begin(9600);
scale.begin(LOADCELL_DOUT_PIN, LOADCELL_SCK_PIN);
scale.set_scale(); // innitially using 1
scale.tare(); // removes offsets
}
void loop() {
// Leitura bruta do HX711
long reading = scale.get_units(10);
float strain = reading * calibration_factor;
Serial.print("Leitura bruta: "); // raw data
Serial.print(reading);
Serial.print(" | Deformação: "); // calibrated data
Serial.println(strain);
delay(1000);
}
If you need more images I can provide, for now they only allow me 3 per post. I'm puzzled... any advice?
