Guys, I have a digital scale bought from China, I want to put a weight alarm on it. I ask how difficult it would be, or if it would be possible, to connect an arduino uno to the output of the 7-segment display and obtain the value of the weight reading in real time as shown in this image. I have nothing here but an old multimeter (which in this case is useless).
It may be possible. However, do your scales have a serial output - some have an RS232 port so they can send weights to other devices such as POS printers.
Conceptually its not hard. in practice, good luck. The strobe lines and segment lines could all be fed in. If the strobe lines were interrupts the coding would be trivial. IRQ fires, specific one tells digit, segments give value, easy peasy.
Wiring, however, may be a different issue.
It is possible to hack and decode custom LCD connections, if you can expose them, but it is very laborious.
See https://www.instructables.com/Direct-Reading-of-LCD-Using-General-Purpose-IO/
This approach to hack a scale is much easier, if it can be made to work: Hacking a Digital Bathroom Scale – scanlime
Or just replace all the scale electronics with your own, using the sensor: https://www.instructables.com/Make-your-weighing-scale-hack-using-arduino/
It has no serial output. And the driver chip of the displays is scraped.
Is there anything I can try ? and give a little luck ? I mean, some code ?
Instructions are in the links I posted. See reply #4.
If you are not willing to put a lot of work into the project, buy a scale with a computer interface.
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or use a load-cell with HX711 ADC-converter.
You read in the weight with the HX711-library and can do with the data whatever you want.
If you post an overview about your project what you want to do in the end
much better suggestions can be made.
20kg Digital Wägezelle Wägesensor + Hx711 Ad Gewicht Verstärkermodul Diy | Fruugo DE(10-20%5D_DE&utm_term=4574655569333034&utm_content=Ad%20group
Thank you guys. I know the HX711, I've done tests with a weight sensor. The question was just the feasibility of reading a display of a trade balance.
jremington in post 4 helped a lot. It's harder than I thought. Especially outside a laboratory with good instruments.
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