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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:
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!
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Based on 26 ratings:
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.
Followed the hookup guide and it worked perfect with my Arduino Uno! Very easy to use with a load cell.
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.
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 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.
Connection to cell are best done soldered directly to load cell. Awesome amplifier.
Had it up and publishing(Uno and Ethernet shield) to broker in 30 minutes.
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.
I have not yet been able to work on my scales projects. I will update this review once I’ve completed the two projects.
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.
This really saved my partner and I for our project and the product got to my home faster than expected.
0 of 3 found this helpful:
FedEx sent my package all over the country. 4 weeks later I still don’t have it.
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.
This is a great product and it’s really easy to install and use. I would definitely use it again.
BEWARE! The HX711 is an analog-to-digital converter! It is not a simple amplifier! I went back and reread the product description and it’s not really obvious from reading the Sparkfun website. After I figured out how to get the data from the thing, everything went smoothly and the weighing systems appears to be accurate and repeatable.
Hey, so as of Oct-2017, the Teensy 3.X core “shiftIn” function that is used by the default HX711 library is too fast. I opened a github issue, pjrc forum post, and sparkfun forum that all link together (as the three threads related to each other.) There’s a simple fix involving a delaymicro(1) in the library code
It’s up in the air as of october 2017 whether this is a HX711 library issue, or a teensy issue, insofar as teensy core is not emulating the slow AVR functionality, but at the same time, to add the delay to the core could disrupt code that relies on the teensy being faster with ShiftIn than the stock.
Anyway, after documenting my problem and getting community help on the fix, although it was a major hassle at first to use the HX711 breakout, it was an awesome demonstration of the community :). I hope it works well for you!
The actual results I’m getting from the HX711 are great. It’s superb to have a 24-bit device so easy to use and relatively cheap :)
Sparkfun should add some clarity on what the excitation voltage is for the HX711 breakout, and not assume everyone will want to calibrate their load cells and/or doesn’t have a datasheet for it. I was expected 4.2V from background reading on the HX711, but measured an excitation of 4.36V, and just a little bit of clarity on that core functionality might be useful. Maybe I didn’t see it in the guide, but the guide seemed to try and abstract what was going on with its calibration example, and may have been more educational if it got into excitation voltages.
A super simple solution with a typically reliable SparkFun “Getting Started” guide! Using with the Sparkfun Redboard and a single 10kg load cell. The reason i shop with Sparkfun, is that I find their product guides understandable and complete. This is another example of a great guide and, of course, it was written by Nathan. I can quickly get started with the features of the project and world domination…
I have a quadruped under construction, and each foot has a load cell to measure paw pressure to assist with balance calculations. I’m using non-SparkFun micro load cells, electrically similar to those SparkFun sells. I interface each HX711 to a 16-bit PIC and that has worked well. When the HX711 DAT signal goes low, indicating data available, it triggers an interrupt and all the CLK pulsing, and DAT reading, is handled by bit-banging in a loop in the interrupt service routine. It’s easy, responsive and low-overhead.
The HX711 amp made the connection simple and easy, and works great!
Easy to use, inexpensive, and very reliable. I love these.
I use three HX711 to evaluate the CG of my RC planes. Works so far fine.
I got this recently to go along with the wheatstone bridge combinator board so I could hack a bathroom scale to use as a load cell in a project. The HX711 made the signal from the strain gages readable with an Arduino. It all works pretty good!