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Description: The SparkFun Load Cell Amplifier is a small breakout board for the HX711 IC that allows you to easily read load cells to measure weight. By connecting the amplifier to your microcontroller you will be able to read the changes in the resistance of the load cell, and with some calibration you’ll be able to get very accurate weight measurements. This can be handy for creating your own industrial scale, process control or simple presence detection.

This version of the SparkFun Load Cell Amplifier features a few changes that you specifically asked for! We have separated the analog and digital supply, as well as added a 3.3uH inductor and a 0.1uF filter capacitor for digital supply.

The HX711 uses a two-wire interface (Clock and Data) for communication. Any microcontroller’s GPIO pins should work, and numerous libraries have been written, making it easy to read data from the HX711. Check the hookup guide below for more information.

Load cells use a four-wire Wheatstone bridge configuration to connect to the HX711. These are commonly colored RED, BLK, WHT, GRN and YLW. Each color corresponds to the conventional color coding of load cells:

  • Red (Excitation+ or VCC)
  • Black (Excitation- or GND)
  • White (Amplifier+, Signal+ or Output+)
  • Green (A-, S- or O-)
  • Yellow (Shield)

The YLW pin acts as an optional input that is not hooked up to the strain gauge but is utilized to ground and shield against outside EMI (electromagnetic interference). Please keep in mind that some load cells might have slight variations in color coding.

Note: Special thanks to Bodge for supplying the Library for the HX711!

Get Started with the HX711 Load Cell Amplifier Guide

Features:

  • Operation Voltage: 2.7V–5V
  • Operation Current: < 1.5mA
  • Selectable 10SPS or 80SPS output data rate
  • Simultaneous 50 and 60Hz supply rejection

Documents:

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Customer Comments

  • Getting the following compile error from Arduino IDE. Library used id from https://github.com/bogde/HX711

    In file included from Loadcell_Sparkfun_code.ino:34: C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:16: error: ISO C++ forbids initialization of member ‘OFFSET’ C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:16: error: making ‘OFFSET’ static C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:16: error: ISO C++ forbids in-class initialization of non-const static member ‘OFFSET’ C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:17: error: ISO C++ forbids initialization of member ‘SCALE’ C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:17: error: making ‘SCALE’ static C:\Users\Jeremy\Documents\Arduino\libraries\HX711/HX711.h:17: error: ISO C++ forbids in-class initialization of non-const static member ‘SCALE’

    Anyone encounter this?

    • What Arduino version and board definition are you using? I was able to install and use that library on 1.6.11 without issue.

      • Updated to 1.7.11 and compiles fine, but now my arduino isn’t recognized by the IDE. Arduino Uno shows up in my “Other Devices” under Device Manager, but I can’t install the driver!

        Windows gives me this when I point it to the driver folder and try to install:

        “windows found driver software but encountered an error while attempting to install it. One of the installers for this device cannot perform the installation at this time”

        Never seen this before in my life, been searching relentlessly online for solutions.

  • The formula for the output voltage AVDD appears wrong in the HX711 datasheet and the SparkFun schematic. I think it should be VAVDD = VBG*(R1+R2)/R2 … not R1 in the denominator. My derivation and measurements support this. I had to dig into this to use VSUP = DVDD = 3.3 V and change the 20 KΩ resistor to a 10 KΩ for a different load cell excitation voltage.

  • To second RobotRacer’s comment, I too would be interested to know where I can find the bare IC so I can use it on my own PCB. I’d buy one from SparkFun if they sold it on its own.

  • Will this work with a pressure sensor where all 4 legs of the wheatstone are variable?

  • Every load cell I try on this thing drifts waaay more than it’s rated - as much as 2% of FS. It seems to drift most with slight temperature changes (10 to 20 deg F). Anyone else having this problem?

  • Any idea what the maximum output impedance of the sensor can be? Those 100 Ohm resistors makes me think it has to be pretty small.

    I have a pressure sensor that’s basically a load cell but the output impedance is 1.5K.

    • 1.5k should be fine. The load cells I’ve used are a little under 2k. The 100 ohm resistors, in conjunction with the 0.1uF capacitor help to reduce noise on the input.

  • Has anyone had any luck finding the HX711 bare IC available anywhere? We are looking to integrate one into a new PCB, up to now we have been using the first version of this board (works great!!!!!!!) for prototyping. We are just ready to make the next step with development and can’t find this chip on SparkFun, DigiKey, Mouser or Arrow. We bought a bunch of these boards and stripped them just to populate some of our boards

    We love using spark fun breakouts for prototyping!

    • Have you tried sending Avia Semiconductor an e-mail and asking them who their U.S. Distributors and/or Reps are? (There are a number of U.S. companies that act as “factory reps” for various manufacturers – my experience is that they’ll be glad to answer “where can I get” questions for companies on their line-card, especially if they know you’re trying to incorporate it into a “product”.)

      Google turned up that the English web page for Avia Semiconductor is http://www.aviaic.com/enindex.asp

      Also, depending on the quantity you’re looking for, you might try asking the “volume sales” at SparkFun – it seems to me that they might be willing to sell you some (at a mark-up from what they pay, of course). The worst they can do is say “no”! (Remember, there’s an old Indian saying “If you don’t ask, you don’t get!” The old Indian who said it was named Gandhi.)

    • JopieK / last year / 2

      AliExpress has some suppliers (I found one with this title: “50PCS HX711 HX711 SOP16”) for only a few bucks.

Customer Reviews

4.3 out of 5

Based on 14 ratings:

Currently viewing all customer reviews.

Small and simple.

It gets the job done. The labels are clear and easy to read. The example code had only one minor issue: include <name> vs include “name” and worked just fine after it was resolved. Thanks for a nice web site with all the cool stuff.

worked great!

Followed the hookup guide and it worked perfect with my Arduino Uno! Very easy to use with a load cell.

It works just like any other HX711

I was comparing this to some of the others that I’ve picked up and really don’t see much in a difference for readings other than it is a bit more expensive. Its nice that they at least have dropped the price a little from when I bought it.

I do have to say the Sparkfun library is great as its probably the most comprehensive when setting up a load cell or tieing in 4 load sensors.

It took me a little researching on the differences between a load cell and a load sensor.

You can tie 1 load cell into the hx711 or you can tie 4 load sensors into this using a wheatstone bride.

Perfect for my sugar rocket motor test stand!

I knew Sparkfun was the place to go to get the components I needed for our experimental sugar rocket motor test stand with data logger. Now we can fine tune the Buder Rocket Boy’s sugar rocket engine formula this winter perfecting a replacement for commercial hobby rocket motors. The XH711 along with the 10kg straight bar load cell (TAL220) was a perfect fit. Precise, compact and at a great price. Thanks guys for designing and supplying awesome stuff!

Well done product

Well designed, works as advertised, documentation and SW is freely available. It took just few minutes to power it up and get good reading. I am very satisfied with this product.

Great board

Connection to cell are best done soldered directly to load cell. Awesome amplifier.

Good value and easy to follow guides for beginners like me

Had it up and publishing(Uno and Ethernet shield) to broker in 30 minutes.

easy to integrate with tutorials

This was my first time using load cells and did not know what to expect. I read the tutorials and got it wired up easily. I got it hooked up to my Arduino and with the library that Sparkfun provides I got it running with no fuss at all. The one problem I had was that the rate that it was updating was not very fast. After some reading I realized it has a jumper on the bottom which if you bridge will increase the data rate. Once I did that it worked perfectly for my application.

Still in the box!

I have not yet been able to work on my scales projects. I will update this review once I’ve completed the two projects.

Easy to use and accurate

This was surprisingly accurate. My load cell was for 780 g max. I calibrated it for 32 g, (two ½-13 nuts) weighted with a scale accurate to .001 g and then tested it up to 320 g. It was spot on.
The one problem I had was in finding the calibration constant. Mine was far different (much larger) than the example given in the tutorial, and the calibration program would have taken forever to slowly find it. I modified the program so it would take bigger steps and zero in on the constant faster.

Really helpful!

This really saved my partner and I for our project and the product got to my home faster than expected.

0 of 1 found this helpful:

4 weeks and I still don't have it.

FedEx sent my package all over the country. 4 weeks later I still don’t have it.

Good product, and remarkably tolerant of my stupidity

Very impressed. Through means of some heavy-duty stupidity on my part, I had to de-solder and re-solder some connections between the amps and the rest of my project multiple times. I thought sure I’d used too much heat and had destroyed the traces, but nope: both of my load cell amplifiers are still working flawlessly.

Related Tutorials

Getting Started with Load Cells

June 11, 2015

A tutorial defining what a load cell is and how to use one.