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.
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 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 17 ratings:
2 of 2 found this helpful:
Tried connecting according to hook-up guide. Followed colour suggestions too literally. Smoked out the transistor. Turns out the WHT/GRN leads are opposite on the TSA606 (which differs from the picture and other descriptions in comments). I’m not sure how this would have smoked the transistor. Both amp and cell were connected so I can’t rule out defective board. I would recommend using E+, E-, S+ and S- instead of colour labels on the PCB, since I have read many reviews about confusion of load cell wire colours. Project is on hold until I get a replacement.
1 of 1 found this helpful:
I do wish you had separated the analog and digital power rails. Right now it works great on 5v but its tricky to use a 3.3v micro because the clock and data pins are at dvcc.
I made it work by unsoldering the dvcc pin and putting 3.3v on it, the put 5v on the VCC solder tab which is now avcc.
1 of 1 found this helpful:
Plugged (correct) leads from load cell to board, connected to Pro mini, loaded test program and success. Biggest problem was the 200kg load cells lead colors did not match spec sheet. Smoked first board trying to find why it didn’t work. Did a 4x4 resistance matrix on the load cell and it was obvious what were the correct connections. Put correct leads into the replacement board and it worked perfectly. A needed product.
Easy to use and well worth the small cost, way to go SparkFun!
The tutorial made it really simple to get readings from a bathroom scale load cell.
The Amplifier board is a plus..it works. It collects the four load cell analog signals, detects the bridge change, performs a A/D and outputs the digital signal to the Arduino. however, you need to explain that there are 2 strain gages at each cell. Use a proper schematic and label inputs as Vcc, Gnd, O+ and O- on the 711 board. Then label the software zero setting that must be tweaked as well as the gain setting. Also Github doesn’t work to insert the library and software. A plus is the system works at 3.5V. Also, the 711 board could have a female connector so that an option is purchasing a 5-ft length of shielded cable to hook to the Arduino. (hardly anyone would put the arduino on the floor with the scale)… I hope this helps to resolve problems by others (the guy who fried a board)…
Easy to setup, clear instructions and tutorial. Works inmediatelly and very well.
I am designing a scale that uses two load cells so I need two channels. i bought this board along with the combinator board. However, the combinator board only allows connection of load cells with three conductors whereas my load cells have four. So, I had to buy a different board that is designed to handle two channels (E+, E-, A+, A-, B+ and B-) Thanks
Long delivery time to Europe.
I want to hack a bathroom scale and there are several for @$14 on Amazon. Anyone know of one that has for certain has the BWR 3 wire sensors that the SparkFun Load Sensor Combinator board is looking for?
I built a scale for counting lams in a motor (at a motor co.) I am systems eng at a major motor mfg co. We now are able to count lams and even small parts with the scales. Works great and things just fell into place. I like that. You did well ( or even great) with this part. I did have to go to a larger load cell.
I built a dog weight scale using this board, 4 Load Sensors, a Load Sensor Combinator board, and an Arduino. To my surprise it worked the first time I turned it on. After a little calibration it gave usable results. I’m impressed by the lack of noise and how easy it was to interface to this board via the HX711 library.
easy to use although the pcb is large
Troubleshooting info would be nice and info on how to best mount the load sensors as well. Thus far I haven’t gotten a usable reading but to be fair, I haven’t been able to find a good calibration value nor have I double checked my soldering as closely as I will likely need to. In terms of finding a good calibration though, I took a stab at adding some automation to the already well used calibration arduino script. You can find it here: https://github.com/thecircleh/eir/blob/master/Calibratescale.ino 5 stars for the product if I can get good readings. UPDATE : 7/9/16. Well I got it to finally work. For my test I simply taped the load sensors into place. Equally spaced in an array of 4. Powered with 3.7 volts. Used a heavier calibration weight (my son) and the above reference script. Voila!!!!
Simple to use and works very well.
Really, you grab the library and you are good to go. Seems to work with all of the normal pins, analog, digital, and interrupt.