I am a university masters student who is currently working with a group of mechanical engineers to built a tabletop tensile and fatigue testing machine. To measure the forces being applied to a sample that is attached to the machine, a DBBSM series 5 S beam load cell will be used with a maximum load capacity of 250kg.

To connect the load cell to a PC / Laptop, a Raspberry Pi 3 has been chosen as the interface between the two devices. How would we connect our load cell to the Raspberry Pi?

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    This question is too broad for this forum. Try to isolate smaller pieces that have discrete answers. – Brick Nov 12 '17 at 17:17
  • You need to do some research. What does the load cell output? Note that the Pi only has digital inputs. – joan Nov 12 '17 at 18:38
  • In general, the GPIO would be used when connecting sensors to the RPi. You will need the datasheet on the sensor, some electronics knowledge to interconnect the sensor with the RPi GPIO, and some programming skills to retrieve the sensor data from the data stream. – RubberStamp Nov 12 '17 at 19:03

The magic word you're looking for is HX711: namely, Avia Semiconductor's 24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales. The HX711 converts load cell Wheatstone bridge outputs to digital pulses. There are a number of breakout boards for the HX711, including the SparkFun Load Cell Amplifier board.

There are a number of Python libraries that purport to read HX711 output via GPIO. I can't recommend any one in particular, as I haven't tried any of them.

  • To be honest, a Raspberry Pi is complete overkill for this, and much harder to interface to a PC than an Arduino. The SparkFun OpenScale board may even do all you need – scruss Nov 14 '17 at 12:52

You will need to connect an Analogue to Digital Converter (ADC) between the Load Cell and the Raspberry Pi. You may need to pay attention to the voltage levels from the load cell to ensure that the ADC can handle the full range. The following tutorial will help you wire the system up

Finally, you will need to spend some time calibrating the system by loading the S beam with varying weights and recording the digital reading received by the Raspberry Pi.

  • Hello and welcome. Please take the tour and visit the helpcenter to see how things work here. It is noteworthy that the output of a load cell is probably in the millivolt range, so a "simple" ADC circuit might not be enough. This calls for a somewhat higher engineering effort, which on the other hand might be a question better suited for electronics.stackexchange.com – Ghanima Nov 13 '17 at 6:50
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    @Ghanima yes, you are correct. The load cell signal will need considerable amplification. My mistake. – Colin Dickie Nov 13 '17 at 16:46

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