Getting more from a digital bathroom scale

January 21, 2019

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  vidposter.jpg

 This idea was in my mind since decades but just don't want to waste a whole arduino for a single i/o operation which draw less than 2watts.

 
 Recently discovered digispark which is an ATtiny85 powered development board costs around $5. It's smaller than arduino pro mini which makes it perfect fit for wearables and iot projects.
 
 There is already wifi/bluetooth enabled bathroom scales available on the market but they're expensive and only sending data to their own application with a custom protocol. My setup costs around $10 and took one hour to deploy. It's collecting sensor values from hx711 load cell amplifier and transferring this information to pc with 443mhz wireless link. I attached a wireless receiver to previously mentioned sensor station which collecting the data and pushing it to my virtual assistant software called "Judith"

 How is the data processed
 I created a script that groups the same values in array and deciding the gross value by getting value of largest group. Previously i tried to take average of incoming data but this method provides more accurate readings.
 
 Virtual assistant writing that value to database and providing voice feedback after that. Also created a JSON api endpoint for chart visualization purposes.

 Assistant software is mostly turkish, planning to release it to public after a translation and some makeup but you can take a look to arduino sketch if interested with creating a similar setup.
 
 Shopping list
 + Bathroom scale - $8
 + hx711 load cell amplifier - $2
 + digispark dev board - $3
 + 443 mhz transmitter - $1

 arduino compatible source code available in here: https://gist.github.com/PsyChip/d716c55f6b908ae7ae43c19cce6924ea

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