View source for Component: Bridge Amplifier (HX711 / BL0122 / BL0132) (Force)

{| style="width:50%"
|-
| width="20%" style="color:gray;" | Author
| Matrix TSL
|-
| width="20%" style="color:gray;" | Version
| 2.0
|-
| width="20%" style="color:gray;" | Category
| Force
|}


==Bridge Amplifier (HX711 / BL0122 / BL0132) component==
The HX711 wheatstone bridge amplifier is used to get measurable data out from a resistive bridge. Common examples include load cells, strain gauges or pressure sensors.

==Detailed description==























''No detailed description exists yet for this component''

==Examples==

A simple example showing how to get a meaningful reading out of the HX711 IC connected to a load cell sensor. Zeros/Tares the reading when the switch is pressed.


{{Fcfile|HX711_Example.fcfx|HX711 Example}}



The scale factor was determined by performing calibration with a unity scale of 1.0 and fixed weight weights. A table of weight vs reading was constructed to provide the correct scale factor.


Here is a guide to calibrate your sensor


When 0g was present on the load cell we zero the output.


When 10g was present on the load cell we get a reading of approx 2170. 

2170 / 10g = 217 per g.


When 20g was present on the load cell we get a reading of approx 4340. 

4340 / 20g = 217 per g.


1 / 217 = Scale Factor of 0.004608


The readings may not be 100% linear so it's best to take several samples based on different weights across the range you want to be able to measure and from this you can work out a close fitting average.

==Macro reference==

===Initialise===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''Initialise'''
|-
| colspan="2" | Sets up the I/O ready for communications with the HX711 IC and performs an initial sample to set the channel and gain. Must be called before calling other HX711 component macros.&nbsp;
|-
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-void-icon.png]] - VOID
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===RawSample===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''RawSample'''
|-
| colspan="2" | Allows the HX711 to be directly read returning the raw unscaled 24-bit reading. Reading is relative to the last defined Zero point. If a timeout occurs and the HX711 is not ready then we return the last valid reading.&nbsp;
|-
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-s32-icon.png]] - LONG
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===ScaledSample===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''ScaledSample'''
|-
| colspan="2" | Takes a raw sample and then applies the scaling factor to return a real world value.&nbsp;
|-
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-f32-icon.png]] - FLOAT
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===SetChannelAndGain===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''SetChannelAndGain'''
|-
| colspan="2" | Allows the preselected input channel and gain to be overridden.&nbsp;
|-
|-
| width="10%" align="center" | [[File:Fc9-bool-icon.png]] - BOOL
| width="90%" | Channel
|-
| colspan="2" | Range: 0-1 / 0=A 1=B&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-u8-icon.png]] - BYTE
| width="90%" | Gain
|-
| colspan="2" | Channel A can be 128 or 64, Channel B can be 32&nbsp;
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-void-icon.png]] - VOID
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===SetSampleCount===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''SetSampleCount'''
|-
| colspan="2" | Specifies the number of samples to perform when taking a reading. The more samples the more filtered the signal will become from high frequency noise.&nbsp;
|-
|-
| width="10%" align="center" | [[File:Fc9-u8-icon.png]] - BYTE
| width="90%" | NumSamples
|-
| colspan="2" | Default 1. Range 1-20&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-u16-icon.png]] - UINT
| width="90%" | Delay
|-
| colspan="2" | Time to wait between samples in milliseconds.&nbsp;
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-void-icon.png]] - VOID
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===SetScaling===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''SetScaling'''
|-
| colspan="2" | Sets the scaler for the samples to provide a meanningful value. Default scaler is set to 1.0&nbsp;
|-
|-
| width="10%" align="center" | [[File:Fc9-f32-icon.png]] - FLOAT
| width="90%" | Scaler
|-
| colspan="2" | Unity Scale = 1.0&nbsp;
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-void-icon.png]] - VOID
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


===Zero===
{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-comp-macro.png]]
| width="90%" class="mtx-class-macrohead" | '''Zero'''
|-
| colspan="2" | Zeros the reading at the current sample&nbsp;
|-
|-
| width="10%" align="center" style="border-top: 2px solid #000;" | [[File:Fc9-void-icon.png]] - VOID
| width="90%" style="border-top: 2px solid #000;" | ''Return''
|}


==Property reference==

{| class="mtx-class-macrotable wikitable"
|-
| width="10%" align="center" class="mtx-class-macrohead" | [[File:Fc9-prop-icon.png]]
| width="90%" class="mtx-class-macrohead" | '''Properties''' 
|-
|-
| width="10%" align="center" | [[File:Fc9-type-16-icon.png]]
| width="90%" | Input Channel
|-
| colspan="2" | Selects which channel to sample A or B. Gain settings are channel specific.  A Gain can be 128x or 64x B Gain is fixed at 32x&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-16-icon.png]]
| width="90%" | Input Gain
|-
| colspan="2" | Gain settings are channel specific.  A Gain can be 128x or 64x B Gain is fixed at 32x&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-5-icon.png]]
| width="90%" | Data
|-
| colspan="2" | Data pin - connected to HX711 Data Out pin.&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-5-icon.png]]
| width="90%" | Clock
|-
| colspan="2" | Clock pin - connected to HX711 SCK pin.&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-21-icon.png]]
| width="90%" | Clock Transition Delay
|-
| colspan="2" | Number of microseconds to wait after each clock edge. Max theoretical: 10Hz Mode = 1uS / 80 Hz Mode = 4uS&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-7-icon.png]]
| width="90%" | Wait For Clock Low
|-
| colspan="2" | Waits for the clock to go low when performing a sample signifying that a new sample is ready to be collected.&nbsp;
|-
| width="10%" align="center" | [[File:Fc9-type-7-icon.png]]
| width="90%" | Use Median Filter
|-
| colspan="2" | &nbsp;
|}

==Component Source Code==

Please click here to download the component source project: [https://www.flowcode.co.uk/wiki/componentsource/FC_Comp_Source_Load_Cell_HX711.fcfx FC_Comp_Source_Load_Cell_HX711.fcfx]

Please click here to view the component source code (Beta): [https://www.flowcode.co.uk/FlowchartView/?wfile=componentsource/FC_Comp_Source_Load_Cell_HX711.fcfx FC_Comp_Source_Load_Cell_HX711.fcfx]