Component: Load Cell (HX711) (Force)

Author	Matrix TSL
Version	2.0
Category	Force

Load Cell component

The HX711 load cell amplifier is used to get measurable data out from a load cell or strain gauge.

Component Pack

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.

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.

Downloadable macro reference

	SetScaling
Sets the scaler for the samples to provide a meanningful value. Default scaler is set to 1.0
- FLOAT	Scaler
Unity Scale = 1.0
- VOID	Return

	ScaledSample
Takes a raw sample and then applies the scaling factor to return a real world value.
- FLOAT	Return

	Zero
Zeros the reading at the current sample
- VOID	Return

	RawSample
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.
- LONG	Return

	SetChannelAndGain
Allows the preselected input channel and gain to be overridden.
- BOOL	Channel
Range: 0-1 / 0=A 1=B
- BYTE	Gain
Channel A can be 128 or 64, Channel B can be 32
- VOID	Return

	SetSampleCount
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.
- BYTE	NumSamples
Default 1. Range 1-20
- UINT	Delay
Time to wait between samples in milliseconds.
- VOID	Return

	Initialise
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.
- VOID	Return

Property reference

	Properties
	Input Channel
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
	Input Gain
Gain settings are channel specific. A Gain can be 128x or 64x B Gain is fixed at 32x
	Data
Data pin - connected to HX711 Data Out pin.
	Clock
Clock pin - connected to HX711 SCK pin.
	Clock Transition Delay
Number of microseconds to wait after each clock edge. Max theoretical: 10Hz Mode = 1uS / 80 Hz Mode = 4uS
	Use Median Filter