Build a Wi-Fi Smart Scale

There are plenty of ways to monitor changes in your weight. You can get a vague idea from the fit of your pants or the notch on your belt. But anyone who’s serious about getting or staying in shape must step on the scale to get the cold, hard truth in pounds or kilograms.

Instead of just buying one, [igorfonseca83] decided to burn a few calories and build his own smart scale that uses IFTTT to send weight data to his fitness tracker. It’s made from four 50kg load cells that are sandwiched between two pieces of plywood. An HX711 sensor module reads the load cells, and a FireBeetle ESP8266 uploads the data to Adafruit IO. His weight is simultaneously displayed on a FireBeetle LED matrix.

We applaud [igorfonseca83]’s efforts to make this an easy, educational project that anyone can replicate. The instructions are great, the pictures are clear, and there’s even a CAD animation of all the pieces coming together. Jog past the break to see the build video, and weigh in down below.

9 thoughts on “Build a Wi-Fi Smart Scale

  1. “anyone who’s serious about getting or staying in shape must step on the scale to get the cold, hard truth in pounds or kilograms”

    I’m not sure that is correct. No, I’m not one of those people that ignore health science and try to say you can be any size you that you want to be and it is good. Weight isn’t really the best, most reliable measure though. I’ve known plenty of people that weigh in as obese because they are so muscular. Likewise I know plenty with “healthy” weights but not an ounce of muscle beyond the bare minimum that get winded by a walk up a single story of stairs.

    If you exercise you know if you are in shape or not. Just master being honest with yourself and you will do fine!

    If you don’t exercise… well.. you probably aren’t in shape. If you think it’s all good because you get the exercise you need at work… yeah, you are probably not in shape. Unless your job is to not drive but be the forklift… your job feels like exercise because you are too out of shape for it. Fix that!

    1. closed loop control of any variable requires feedback, so weight alone is a good start in that feedback loop. Other good indicators include body fat %, heart rate, breathing rate, and any other biometric data that can be used to determine energy output. The idea is that by knowing energy output and change in mass, one would be able to modify work out routines as well as dietary needs in order to achieve optimal bodily function.

      The problem lies in your definition of serious, from my standpoint all of the advice that you have given and the scenario that you have described sounds like someone who wants to casually get into shape. To be frank, for anyone who wants to start getting into shape it is fantastic advice and i would whole heartedly concur with you that weight is not really important for anyone who just wants to get into better shape. The difference is that there are people who are serious about it and that usually requires regularly weighing yourself. For example take any athlete that competes and im not talking the obvious examples of fighters who have to hit a specified weight class, competitive athletes are always trying to maximize their power output while minimizing their weight as any extra weight is just more work to drag around. Those are the people i consider to be serious about getting or staying in shape, they are also the ones most likely to weigh their food as well.

  2. A excellent project, very practical, and very useful for the average person. The video is slick, even the load cells are linked to the supplier.
    As a owner of a Fitbit WiFi scale which is dodgy to configure and very inaccurate due to non repeatability, I have also been thinking of building my own as I weigh myself every day and log it.

    Nice job!

  3. For anyone that has tried to build a precision load cell preamp, it is astonishing that you can buy a complete 4-channel preamp, signal summer, 24-bit digitizer and digital interface that draws less than 5 milliwatts, for less than the cost of a cup of coffee. Just amazing.

    I bought a similar scale (but sans Wifi, glass instead of plywood, and LCD instead of eye-searing blue LED) for under $20 next-day delivery. I’ve had it well over a year. Used 3-4 times daily, it gets over a year out of a single CR2032, and is spot-on repeatable and accurate. I’m astounded.

    I don’t understand the wifi part though (which is why I didn’t buy one with it). I mean, you’re standing on it — you can read the numbers just fine without involving a server in a different country (or needing a wall plug for power). My SO writes them down and plots it, but I just check if I’m in the deadband. (yeah, my SO is a PID person, I’m more bang-bang.)

    1. A friend of mine hacked a commerical scale about 5 years ago to give him wifi.
      Everytime he stepped on it in the morning it logged his weight to his server.
      He was “hacking his weight” doing it as a programming project, call it bug fixing.
      His graphs of weight over time showed things were working and TBH he sold me on it.
      It worked for him and he went from being quite overweigh to needing to go to a gym.
      The historical record is also nice.

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