Strain Gauge Meter With HX711

Hi I am Berkay

I want to make strain meter. This strain meter can be quarter bridge, half bridge and full bridge. This system can use with 120 ohm and 350 ohm strain gauges. Because you can set with potentiometer. On the other hand this system send information your pc with bluetooth. So you can use it remotely.

I have 2 problem.

First problem is hx711 is unstable. I tried to create a millivolt meter with hx711. I could not calibrate. Because HX711 calibration curve is not linear. I don’t know how to make stable millivolt meter with hx711. Then i will convert millivolt to straine. I would be very happy if you could help me with this subject or acts as a code to measure strain.

Second problem is I’m not sure this system will work. What do you think about it ? I would appreciate if you share.

Best Regards.

You can find the calibration curve and system information in the appendix.

Did you really power everything with 3volt, or is this another Fritzing failure.
HX711 and BT modules and pots should be powered from the 5volt pin of the Arduino.
The Nano should be powered via USB, or externally with 6-9volt on the V-in pin.
A HX711 needs more than 4.5volt to be stable.

Thank you very much for your answer. This is just prototype. I have not installed this system before. I will pay attention to this warning when i will set this system. But I tried hx711 like this.

  1. I connected A+A- with power supply for send known milivolts.

  2. I connected Vcc - Arduino 5V, GND - Arduino GND, DT SCK - A0 A1

Then first I sent 1 mV from power supply and I redorded the this data. Then I recorded other datas for other milivolts. Finally I found line equation of this data sets. But I saw hx711 is not stable. How can it stable ? Or how do I make millivolt meter with hx711. or where am i doing wrong ?

Then first I sent 1 mV from power supply...

Can't do that, unless you made sure you're inside the common mode window of the HX711 inputs.
Which is between about 1.2volt and 2.9volt above HX711 ground.

Thanks. I will try that. Then I share my results. Do you have other advise, link, code about my project ?