Can't get constant reading with load cells

Question

I'm really a newcomer to arduino and I'm trying to build a scale with four SEN-10245 load cells and a HX711. My issue is that I can't get constant readings in the serial monitor and I'm not sure if my coding is right or if I did the right setup. I made the following setup, based on some examples I found online:

The code I'm using is as follows:

    #include <hx711.h>
    Hx711 scale(A1, A0);
    void setup() {
    Serial.begin(9600);
    }
     void loop() {
     Serial.println(scale.averageValue());
     delay(200);
    }

link for the library github: https://github.com/aguegu/ardulibs/tree/master/hx711

Please help me, i'm a total beginner.

Answer 1

Assuming everything is hooked up correctly, your issue is likely related to electromagnetic noise (aka electromagnetic interference, EMI). Load cells output very small voltages, which is why you need the HX711 amplifier. Your long wires are essentially acting as antennas, picking up the electromagnetic noise in the room. One easy way to reduce the noise is to twist the wires together. You can also shield the wires by wrapping them with aluminum foil and attaching the foil to ground.

Making the wires much shorter would likely also help. That would be a good test to see if it helps.

The power supply could also be creating noise. I have found that the 5v line coming from a computer is often quite noisy. This is harder to fix, but an easy way to test if this is the issue is to power the Arduino with a 9V battery. Just make sure you plug it into the Vin pin, not the 5V pin, because the 9V needs to be regulated down to 5V.