Tools, APP Software Used etc.

	KiCAD Kicad
	Falstad circuit simulator

Description

Self-contained PCB weighing scale

Note! Please follow the attached interactive BOM. It will help you to find the correct components and it will also guide you with the placement.

I recently published a project where I tried to utilize the traces on a PCB as a strain gauge in order to use the PCB as a weighing scale (or “bending load cell”). The concept was simple: I created a cantilever beam section on the PCB and I placed a pattern of copper traces on this bending part that is similar to the pattern of the conductive traces in a strain gauge. Unfortunately, the concept did not work, because the pattern had too low resistance and an even smaller change in resistance when the PCB was bent. However, when I put a strain gauge on the cantilever beam part, the concept worked perfectly. But, due to structural limitations, I could not measure more than 200-250 grams.

Therefore, I decided to reiterate the project and create a better version of this concept. Since I knew that the PCB traces won’t work, I kept using strain gauges in this design. I also replaced most of the circuitry. The whole Wheatstone bridge is now made of strain gauges (full bridge configuration). This bridge is then managed and measured by an HX711 module. The module is read by an ATTiny85 microcontroller and the results are printed on a small OLED display. The PCB also has a built-in LiPo battery with a charging circuit (MCP73831T).

Schematic and Layout

My website

https://curiousscientist.tech/blog/pcb-weighing-scale-ver2

Direct link to the YouTube video

https://youtu.be/Ffn_Cgs6D_U

Download BOM(Bill of materials)

Oct 31,2022

1,849 views

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Self-contained PCB weighing scale

2 Layers PCB 60 x 70 mm FR-4, 1.6 mm, 1, HASL with lead, Green Solder Mask, White silkscreen

Who needs load cells when you can use the PCB?

1849

10.00 (1)

Published: Oct 31,2022

BOM(Bill of materials)

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Topic

DIY Electronics

DIY load cell strain gauge attiny lipo charger oled display wheatstone hx711

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Ram Gupta
Sir Very Influenced with yor project I'd like to have your gerber files so that I can Modify it and add a Microcontroller

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May 04,20249 Comments
Curious Scientist 2024-05-05 05:24:09Reply
Hi! Sorry, the Gerber files are not public. Also, there's already an ATtiny85 microcontroller incorporated into the board.
Ram Gupta 2024-05-19 00:32:42Reply
Reply@ Curious Scientist：
What to program the ATtiny 85? and also I was planning to add ESP12F Microcontroller for my application can you please help in that?
Curious Scientist 2024-05-19 03:39:39Reply
Reply@ Ram Gupta：
You can search Google for this information... You can make any Arduino as a programmer. I don't work with ESP32.
Ram Gupta 2024-05-19 20:03:00Reply
Reply@ Curious Scientist：
I meant to say that what do you upload on that cutie ATtiny? (i.e. the Driver code for the OLED and the data conversion/calibration code for the values from starin guages) I want to see the logic of the program and what were the values that are the OLED in video they were about 6 digits you didn't explained what were they
Curious Scientist 2024-05-19 20:14:09Reply
Reply@ Ram Gupta：
The code is available on my Patreon.
Ram Gupta 2024-05-23 14:05:54Reply
Reply@ Curious Scientist：
Will the Gerber Files also be available on your Patreon? (Just asking)
Curious Scientist 2024-05-23 23:29:13Reply
Reply@ Ram Gupta：
Hi! No, as I wrote initially, the Gerber files are not public. That means that it is not available at all. If someone really wants the board, they can order it from PCBWay via my project pages. Part of the reasons why I don't publish the Gerber files is that if I made them available, then people could just manufacture them at PCBWay's competitors and use their services. Since PCBWay supports my work, I don't want my design to be manufactured elsewhere. "You scratch my back, I will scratch yours". :) Also, the design files are my intellectual property and I don't want them to be spread on the internet.
Ram Gupta 2024-05-24 12:21:46Reply
Reply@ Curious Scientist：
Thank you so much for your detailed explanation and all the help you've provided with your projects. I completely understand and respect your decision to keep the Gerber files private to support PCBWay and protect your intellectual property. It makes perfect sense, and I appreciate you clarifying it for me. Thanks again for all your assistance!
Curious Scientist 2024-05-24 22:00:47Reply
Reply@ Ram Gupta：
Thank you for being so understanding! Cheers!
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