Build Instructions

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• 1

  Tools and Materials

  The following tools and materials were used in this project:
  

  Tools and materials:

  • 3D printer (link). It was used for printing the case where the electronics are encloused.
  • Solder iron and wire. Some of the components (ESP8266 Firebeetle and LED matrix cover, for instance) doesn't come with soldered terminals. I needed to solder some wires or pins in order to connect those devices.
  • Shrinking tube. l also had to solder the wires of each load cell. A piece of shrinking tube might be used for a better isolation of the conductors.
  • Screwdriver. The structure is mounted using some screws. A set of screwdrivers was used.
  • Screws. I used some screws to attach the 3D printed parts to the base of the scale.
  • M2x6mm Bolts. They were used for mounting the electronics inside the case.
  • 1.75mm PLA (link / link / link) of any color you want.
  • FireBeetle ESP8266 dev board. It's really easy to use and program using Arduino IDE. It has built-in Wi-Fi module, so you can use it in a variaty of projects. It has a connector for a 3.7V battery, which was really usefull for assembling this project. I has also a built-in battery charger. It will recharge the battery when connected to an USB plug. You can also use other ESP8266 based bords (link / link / link) if you wish. Deppending on the board you choose, it would be a little more difficult to connect and recharge the battery, or to connect the LED matrix. The dimensions of the case will also need to be verified.
  • Firebeetle covers - 24x8 LED matrix. This module easilly fits on top of the Firebeetle ESP8266 dev board. I used it to display the values measured by microcontroller, display some status, etc. You can also use other kinds of display if you wish, like ordinary LCD displays (link / link) or OLED displays (link / link).
  • HX711 module (link / link / link). This works as a load cell amplifier. Four strain gauge load cells are connected to this module, and it communicates on a serial communication with the ESP8266 microcontroller.
  • 50kg load cell (x4); (link / link). They are used to measure the weight of the user. Four of them were used for a maximum weight of 200kg.
  • Micro USB cable;
  • 6 female-female jumper wires;
  • 2 x 15 mm plywood sheet (30 x 30 cm). It was used for the base of the scale.

  The links described above are only a suggestion of where you can find the items used in this tutorial (and support my future hacks). Feel free to search for them elsewhere and buy at your favourite store.

  I used a FireBeetle ESP8266 dev board, which was kindly supplied by DFRobot. It worked perfectly! I also tested the code with a NodeMCU board. It also worked fine (although the time for connection was significately longer... I still don't know why...).

  Did you know you can buy a Anet A8 3D printer for only $168.99? Get yours! http://bit.ly/2x04H5B

• 2

  3D Modeling

  The smart scale was desgined using Fusion 360 CAD software. The model is composed of three different 3D printed parts: cover, case and foot. The case provides an enclosure for the electronics, protecting them from physical contact. Electronics are attached in the cover part (using some bolts). This part has a front visor, where the display is fitted. Load cells fit into the foot part, which allows the sensors to be attached to the base.

• 3

  3D Printing

  You can download all the stl files on the following websites:

  https://www.thingiverse.com/thing:2934791

  https://pinshape.com/items/45555-3d-printed-diy-wi-fi-smart-scale

  https://www.youmagine.com/designs/diy-wi-fi-smart-scale

  https://cults3d.com/en/3d-model/gadget/diy-wi-fi-smart-scale

  https://www.myminifactory.com/object/3d-print-diy-wi-fi-smart-scale-66654

  I printed the whole structure in PLA, usign two different colors. The whole print took me around 5h30, using 0.2 mm resolution and 10% infill. No supports needed.

  This is a experimental prototype. Notice that it was designed for a given ESP8266 dev board model (the ESP8266 Firebeetle).

  If you don't have a 3D printer, here are some things you can do:

  • Ask a friend to print it for you;
  • Find a hacker/maker space nearby. The parts used in this model can be printed quickly. Some hacker/maker spaces will only charge your for the materials used;
  • Buy your own 3D printer. You can find the Creality3D CR10 for only $359.99! Get yours at http://bit.ly/2JIUVrf
  • Improvise! You can try to assemble a structure without 3D printed parts.

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