DIY Scale instructions
This page will guide you through all the steps to build your own scale.
You just need some skill, all the materials needed and the software is explained here.
Tools
Soldering iron
A thin soldering tip is advantageous
1.3 and 2 mm hexagonal
It depends somewhat on which screw heads the selected screws have.
3D printer with 0.2mm nozzle
The print space must be at least 135 x 125 x 13 mm. An SLA printer probably offers more details but printing is also possible with FDM.
Tweezers
I recommend tweezers, because the scale contains a lot of tiny parts
(Optional).
Cutting pliers
A small pair of pliers to shorten the cables, a pair of scissors is actually also sufficient.
(Optional)
Abisolierzange
Stripping the thin cables is also possible with fingernails, but much more convenient with a tool.
(Optional).
Hardware
Some items link directly to the manufacturers.
In addition, I give here a shopping list for the hardware small parts, these can be ordered almost all on Mouser.de:
PLA / ASA
PLA or ASA, for example, can be taken as the printing material.
24x threaded insert (2.5mm M2)
The threads are melted into the plastic with heat. The 3d models are designed for 2.5mm height and 3.2mm diameter.
Screws
- (20x) 4 mm M2 screws
- (4x) 10 mm M2 screws
- (4x) 10 mm M3 screws
Solder
Thin solder is best, as not much is needed.
Insulating tape / heat shrink tubing
Thin heat shrink tubing is advantageous to protect the solder points.
Mikrousb Cable
To load the scale and to initially install the software.
0.6 mm Cable (30 AWG)
- Red
- Black
- Green
- Blue
- Yellow
- White
- Gray
(2x) Battery adhesive strip
To attach the battery, two adhesive strips are used, which are usually sold in pairs for cell phones.
(1x) Jst PH 2.0 2-pin connector
Needed to connect the battery to the board. May not be needed with a new board or different battery.
(1x) Huzzah 32 Feather Board
The advantage of this board is a LiPo charger, which means that no additional board is needed. Currently, however, an alternative is being sought, which consumes less power.
(2x) Sparkfun TAL 221 - 500 G
These load cells were chosen for their low height.
(2x) Sparkfun HX711
These boards convert the analog signal of the load cells into a digital signal. Possibly this is still changed into a board or an ADS1231 is used.
(3x) WS2812B LED
The LEDs are used as status indicators.
(2x) Adafruit 7 Segment Display & Backpack
2 displays are needed to show larger negative numbers (e.g. -123.5) and a timer is also shown.
(1x) Piezo Summer (optional)
A piezo buzzer is used for sound feedback when pressing keys.
(2x) Touch Button
Illuminated touch buttons are used for input, so the hardware can be completely protected by the case.
(1x) Mikroe 3000 mAH li-Polymer
A large battery provides the power supply. Currently, the battery lasts about a week with the Huzzah32, which can possibly be greatly improved by a board with better power management.
3D Models
To print the 3D models, a print space of at least 135 x 125 x 13 mm is required as described above.
I recommend a 0.2 mm print nozzle and have used the following (Cura) settings:
- Layer thickness: 0.16 mm
- Line width: 0.3 mm
- Wall thickness: 0.9 mm
- Top layers: 7
- Bottom Layers: 7
- Infill: 15 %
- Infill pattern: cube
- Slicing tolerance: Exclusive
Software
Installation
Es gibt verschiedene Wege die Binärdateien auf den ESP zu flashen. Die hier gezeigte Methode benötigt keine Installation zusätzlicher Programme.
- The Flash Download Tools can be downloaded from Espressif and unzip it
- Download the latest software.zip file from Github and unzip it
- start flash_download_tool.exe
- Connect Huzzah32 to PC via USB
- Select Esp32 and press OK
- Select files and enter correct settings
- Flash via START
- After finishing, unplug the Huzzah32
Setup
The setup of the scale will be explained here later.
Calibrate
Information about the calibration of the scale.
Development
This project is currently still under development, as there are still some vulnerabilities, which should be removed.
Currently, the following things are being developed:
Hardware
- Reduce power consumption (other microcontroller)
- Test HX711 alternatives
- Other (waterproof) charging option
Software
- Zero value changes slowly when there is no weight on the scale (drifting)
- Detect when charging
- Evaluate error messages better
- Protect the scale settings with a password
- The timer should start automatically in the future
English 
German 
This is looking awesome! Also very detailed descriptions. I really want to use your scale approach but I am insecure how capacity buttons are working here? Are they covered by the printed case? It would be awesome if you could elaborate on this for the sake of making it easier for me! I am thinking of printing a slightly bigger “weiging waggon” and then from a plaster mold I would make a silikon cover with a little skirt to make it harder for water to enter and make it easy to keep clean. Have you tried such an approach? It… Read more »
Hi thanks for the comment. Yes the buttons are hidden behind one layer of 3d printed plastic. In the technical documents of the buttons it states: Distance between Button and cover: “Maximum distance between overlayand acrylic/glass:0.015” [0.38mm] Material thickness: “Maximum thickness of acrylic/glass, 0.118” [3mm]” I am not really using it because i bought another scale it was more a fun project. A silicon cover sounds great but make sure it doesn’t bend and make faulty readings. I think a hardware switch is not necessary because the esp can go into deepsleep and almost use no energy and can be… Read more »