Arduino Uno - HX711 Digital Weight Scale

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Need to weigh anything? A Bearded Dragon perhaps?

Check out the video above for details on the scale and see it in action.

Soooo...the latest member of our family, a bearded dragon named DaVinci had a stomach bug which was really messing with his appetite, etc... We needed a scale with a resolution in the grams/oz. range but with a big enough base to hold him in his entirety so we could make sure he was on the rebound to health with his diet. Gotta eat those BUGS BUDDY BOY! Arduino and HX711 Load Cell weight scale to the rescue. Read on to build one for your reptile family members, or for whatever you need to weigh.

Step 1: Parts Needed:

Any reference to merchants and particular parts is just that, reference. Caveat Emptor.

  • Bearded Dragon
  • 5kg Load Cell and HX711 Combo Pack Kit - Amazon
  • NOTE for the kit above: One side both holes tapped M4 thread, the other side both holes tapped M5 thread.
  • Arduino UNO - Amazon
  • Precision Steel Scale Calibration Weight Kit - Amazon
  • For Parts: 4 wheel 2 layer Robot Smart Car Chassis Kit Amazon (I used the acrylic bases and standoffs from a previous project I had built, so parts were already present for me)
  • LCD 1602 w/I2C Serial Backpack - Amazon
  • Jumpers, USB Cable

Step 2: Software Needed:

Assumptions:

  • Knowledge of Arduino IDE.
  • Knowledge on installing and utilizing Arduino libraries.
  • Knowledge of obtaining libraries from GITHub.

Libraries:


Final Arduino Sketch:

  • See attached.

YouTube Resource I Used:

  • Ralph Bacon's Videos and Downloads I used for this project. Ralph Bacon

Step 3: Hardware Setup:

This is where YOU need to get creative based on what you have on hand for building the scale frame. Whether it's like mine or if you just want to use some Popsicle sticks and 2X4's...it's your call.

Regardless of how you assemble it, just pay close attention to connection locations and jumper cable lengths you'll be using.

Power Up and TEST your connections once, or twice, before you put it all together.

IMPORTANT NOTE: Make sure all solder joints are completely and solidly soldered on the HX711. It is very sensitive to external EMF. One of my connections was off just a little and the numbers went HAYWIRE! I would wave my hand 3 foot above the rig and it would stop dead in it's tracks.CRAZY MANNNN....CRAZY!!!

WIRING:

Arduino LCD HX711 LOAD CELL

Arduino 5v--------------------5v LCD

Arduino 3v--------------------3v HX711

Arduino Grnd----------------Grnd LCD

Arduino Grnd----------------Grnd HX711

Arduino 10--------------------Clck HX711

Arduino 11-------------------- Data HX711

Arduino A4--------------------Data LCD

Arduino A5--------------------Clck LCD

HX711 E+-----------------------LOAD CELLRED

HX711 E- -----------------------LOAD CELLBLACK

HX711 A- -----------------------LOAD CELLGREEN

HX711 A+-----------------------LOAD CELLWHITE

DO NOT CONNECT B+ B-


Step 4: Final Step - Home Stretch:

This final step of steps may seem a little chaotic, so jump around at your own pace.

  • In the Arduino sketch, if you are you using I2C for the LCD, you may need to change it's address to match your device. If you don't know it's address, you can download the I2C Scanning Tool from here to track it down. It is named ESP32_Wemos_I2C_Scanner but will work on any Arduino compatible with the Wire.h library.
  • Head to Ralph Bacon's page now for additional tips on calibration.
  • Refer to the Bogde GIT page for tips in the Readme.
  • Calibration Time!! Once you have tested all, and assembled, calibrate your scale....even if you calibrated earlier, do it again now.
  • The HX711 will work on other controllers like the ESP8266 and ESP32. You may need to adjust processor speed though. Refer to Andreas Speiss's page for tips on that.

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    3 Discussions

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    Jimbo5595

    Question 3 months ago on Step 3

    Hello. You have done a very nice job on this Instructable and I am trying to duplicate it. I have attached some images of what I have done. I have reached the point of calibration, and that's where I'm stuck. I've read and followed Ralph Bacon's page and also the Bogde Git page as you suggested. I have uploaded and am running the calibration sketch. My problem is inconsistent readings. The Serial Monitor returns values that are all over the map. For instance, I recently placed an iphone on the scale and got readings of 0, 0 and then 830419. Do you have any thoughts on what I might be doing wrong? Have I mounted the load cell incorrectly? Any thoughts would be appreciated. Thank you.

    IMG-0405.JPGIMG-0406.JPGIMG-0407.JPG
    2 answers
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    johnnyfrxJimbo5595

    Reply 3 months ago

    Hey There. When I first fired mine up, the readings were all over the place and I finally figured out that the solder connections need to be COMPLETE and as clean as possible. The device seems to be very sensitive to ANY type of interference if the connections aren't very tight. BTW...We still use it today...so once you get yours going it's like a Tank! Just can't kill it! Haaaa! Have a Great Thanksgiving!!

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    Jimbo5595johnnyfrx

    Reply 3 months ago

    Hey, thanks very much for the reply. And Happy Holidays to you too.