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104 lines
2.8 KiB
Markdown
104 lines
2.8 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/HX711/blob/master/LICENSE)
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[](https://github.com/RobTillaart/HX711/releases)
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# HX711
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Arduino library for HX711 24 bit ADC used for load cells and scales.
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## Description
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This HX711 library has an interface which is a superset of a library made by bogde.
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Some missing functions were added to get more info from the lib.
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Another important difference is that this library uses floats. The 23 bits mantisse
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of the IEE754 float matches the 24 bit ADC very well. Furthermore it gave a smaller
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footprint.
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## Main flow
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First action is to call **begin(dataPin, clockPin)** to make connection to the **HX711**.
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Second step is calibration for which a number of functions exist.
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- **tare()** measures zero point
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- **set_scale(factor)** set a known conversion factor e.g. from EEPROM.
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- **calibrate_scale(WEIGHT, TIMES)** determines the scale factor based upon a known weight e.g. 1 Kg.
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Steps to take for calibration
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1. clear the scale
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1. call tare() to set the zero offset
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1. put a known weight on the scale
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1. call calibrate_scale(weight)
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1. scale is calculated.
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1. save the offset and scale for later use e.g. EEPROM.
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## Pricing
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Some price functions were added to make it easy to use this library
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for pricing goods or for educational purposes. These functions are under discussion
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if they will stay. Another set of function to add weights together didn't make it in
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the 0.2.0 release, it is on a todo list.
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For weight conversion functions see https://github.com/RobTillaart/weight
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## Notes
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### Scale values for loadcells
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These scale values worked pretty well with a set of loadcells,
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Use calibrate to find your values.
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- 5 KG loadcell scale.set_scale(420.52);
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- 20 KG loadcell scale.set_scale(127.15);
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### Connections HX711
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- A+/A- uses gain of 128 or 64
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- B+/B- uses gain of 32
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### Connections
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| HX711 Pin | Color |
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|:----:|:----:|
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| E+ | red |
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| E- | black |
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| A- | white |
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| A+ | green |
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| B- | not connected |
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| B+ | not connected |
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| HX711 Pin | Color |
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|:----:|:----:|
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| E+ | red |
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| E- | black |
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| A- | blue |
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| A+ | white |
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| B- | not connected |
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| B+ | not connected |
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### Temperature
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Loadcells do have a temperature related error.
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This can be reduced by doing the calibration and take the tare
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at the temperature one also does the measurements.
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Another way to handle this is to add a good temperature sensor
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(e.g. DS18B20, SHT85) and compensate for the temperature
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differences in your code.
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## Operation
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See examples
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