Hi there,
I'm working on a digitial scale for an addition to a hobby project that combines a Raspberry Pi 3B+ with a HX711 and 4 strain gauges from a kitchen scale in a wheatstone bridge configuration. Everything is connected and working but the output is continually counting up on average. I'm at a bit of a loss as to why this could be happening.
I'm using the python code library provided by Endail implementing the HX711 c library (
https://github.com/endail/hx711) in python https://github.com/endail/hx711-rpi-py. I have calibrated the code using the calibrate.py script with a known weight of 449g but I'm certain this also experiences this increase as the calibration output is never the same twice. I haven't changed any of this code and I can't find any information online as to other examples of this happening.
The drift is demonstrated here. The sudden spikes are when I have placed a known weight of 449g on the strain gauges. Otherwise there is no weight on the strain gauges.
Equipment used:
I can send a circuit diagram if requested but it is a bit difficult to see given all the wiring passing throught the breadboard. I also have a temperature sensor and a small OLED screen wired into the GPIO. The HX711 is sharing a 3.3v GPIO pin with the temperature sensor, I read online that this is ok.
What could cause this? I'm reasonably confident in the code as I've made no changes. I believe my wiring is correct as I purposely have routed it through a breadboard for visibility. Could my HX711 be busted? Or my strain gauges?
Any guidance is really appreciated!
I'm working on a digitial scale for an addition to a hobby project that combines a Raspberry Pi 3B+ with a HX711 and 4 strain gauges from a kitchen scale in a wheatstone bridge configuration. Everything is connected and working but the output is continually counting up on average. I'm at a bit of a loss as to why this could be happening.
I'm using the python code library provided by Endail implementing the HX711 c library (
https://github.com/endail/hx711) in python https://github.com/endail/hx711-rpi-py. I have calibrated the code using the calibrate.py script with a known weight of 449g but I'm certain this also experiences this increase as the calibration output is never the same twice. I haven't changed any of this code and I can't find any information online as to other examples of this happening.
The drift is demonstrated here. The sudden spikes are when I have placed a known weight of 449g on the strain gauges. Otherwise there is no weight on the strain gauges.
Equipment used:
- Raspberry Pi 3B+
- Sparkfun HX711
- 4 strain gauges in a Wheatstone bridge configuration salvaged from a kitchen scale. All tested with a multimeter.
- Endail/HX711 run through the python variant HX711-rpi-py
- Wheatstone bridge connected to HX711
- HX711 connected to Raspberry Pi with Data -> GPIO 20, CLK -> GPIO 16. VCC -> 5v, VDD -> 3.3v shared with a temp sensor 3.3v, GND -> GND
- Wheatstone to HX711 with A -> E+, D -> E-, B -> A+, C -> A-
I can send a circuit diagram if requested but it is a bit difficult to see given all the wiring passing throught the breadboard. I also have a temperature sensor and a small OLED screen wired into the GPIO. The HX711 is sharing a 3.3v GPIO pin with the temperature sensor, I read online that this is ok.
What could cause this? I'm reasonably confident in the code as I've made no changes. I believe my wiring is correct as I purposely have routed it through a breadboard for visibility. Could my HX711 be busted? Or my strain gauges?
Any guidance is really appreciated!
Statistics: Posted by k_sld — Thu Feb 08, 2024 5:26 pm