- Tue Dec 18, 2018 11:17 am
#79616
Hi,
I've recently acquired an HX711 board and 4 3-wire 50kg load cells in order to develop a set of scales.
I've read through a few different tutorials on how to set these up (e.g. https://www.instructables.com/id/Arduin ... lls-and-H/)
After following this tutorial, all reads from the device returned '8388608', until I swapped the white and black wire pairings - at which point I started to get what looked like real data.
The numbers hover around 500000 when unloaded, and then increase when load is applied, always by the same amount (i.e. adding 20kg always increases the number by the same amount).
However my main issue is that the correction required seems to vary depending on what weight is added. Some (rounded) numbers for different known weights:
* 500000 1kg
* 505000 10kg
* 530000 20kg
* 550000 55kg
* 575000 90kg
As you can see the increase isn't linear - and has a correction roughly equivalent to 500/weight. The spec for the load cells claims that they are (more or less) linear, which is not what I'm seeing.
The specs for the load cells: https://ae01.alicdn.com/kf/HTB1ZDtuKXXX ... XFXXXI.jpg
I've done the following for debugging purposes:
1. Swapped out the Wemos D1 mini I'm using for a Raspberry PI - same numbers read from the HX711 device.
2. Measured the resistance between the wires on all load cells - approx 800 between red and black/white, and 1600 between black and white on all 4 cells.
3. Tried rewiring the bridge in different ways - only this one seems to produce any data.
So my question is - am I doing something obviously wrong, or should I see about getting a different board? Please let me know if there's any other info you need to help solve this!
I've recently acquired an HX711 board and 4 3-wire 50kg load cells in order to develop a set of scales.
I've read through a few different tutorials on how to set these up (e.g. https://www.instructables.com/id/Arduin ... lls-and-H/)
After following this tutorial, all reads from the device returned '8388608', until I swapped the white and black wire pairings - at which point I started to get what looked like real data.
The numbers hover around 500000 when unloaded, and then increase when load is applied, always by the same amount (i.e. adding 20kg always increases the number by the same amount).
However my main issue is that the correction required seems to vary depending on what weight is added. Some (rounded) numbers for different known weights:
* 500000 1kg
* 505000 10kg
* 530000 20kg
* 550000 55kg
* 575000 90kg
As you can see the increase isn't linear - and has a correction roughly equivalent to 500/weight. The spec for the load cells claims that they are (more or less) linear, which is not what I'm seeing.
The specs for the load cells: https://ae01.alicdn.com/kf/HTB1ZDtuKXXX ... XFXXXI.jpg
I've done the following for debugging purposes:
1. Swapped out the Wemos D1 mini I'm using for a Raspberry PI - same numbers read from the HX711 device.
2. Measured the resistance between the wires on all load cells - approx 800 between red and black/white, and 1600 between black and white on all 4 cells.
3. Tried rewiring the bridge in different ways - only this one seems to produce any data.
So my question is - am I doing something obviously wrong, or should I see about getting a different board? Please let me know if there's any other info you need to help solve this!
