Building a Connected Beer Scale with Blynk
Currently live on Kickstarter: https://www.kickstarter.com/projects/plaato/plaato-keg-the-ultimate-beer-tool-tracks-every-pour
Beer brewers put tremendous effort into building elegant DIY systems for serving their crafted beers. We set out to connect all these kegerators to the internet. By combining simple electronics, a popular wifi-chip and an agile IoT-platform we wanted to let beer brewers know exactly how much beer they have left in their kegs.
We built a bagel-shaped base for beer kegs with three load cells to measure the total weight of the keg. Load cells - typically found in bathroom scales - are affordable, but requires tweaking in both electronics and digital filtering to get the desired precision. After testing load cells from several suppliers and some head-scratching we achieved very little noise while sampling 10 times a second. We realised that we could do better than just measuring current keg weight - we could measure how much beer is disappearing from the keg every 0.1 seconds with a resolution of a few grams. In other words, we could show how much beer is being poured from the keg in real-time.
Real-time data over WiFi
Our new goal required more data to be sent and the delay to be minimal. Luckily, that is already taken care of by the guys at Blynk. Using their firmware library, cloud and app, we achieved a latency of less than 100ms. Data is passed from the scale to the local WiFi-network, via the Blynk cloud and to the app, yet it feels like the scale and smartphone is connected by cable.
Plug and Play Prototypes
Since we already had a published Plaato app by Blynk, adding a new product was as simple as dragging around widgets in the Blynk app and pressing Update Apps. We were able to send out prototypes to pilot customers around the world and iterating on the app functionality together with them. Using Blynk’s dynamic provisioning, test users set up the prototype in the app just like they set up our existing product. Once the feedback started coming in, we updated Blynk widgets several times a day to see what worked for the test users.
From Prototype to Production
Bringing an idea from a working prototype to a mass-produced unit is often a bigger challenge than expected. You will encounter difficulties in plastics, electronics and assembly. But the (not at all insignificant) internet-part of the product is already ready and we can focus on making the best possible product.
Tarje Sandvik, Embedded Systems Engineer, Plaato Inc
Tarje Sandvik said:
Each load cell is full-bridge, so we are connecting three full-bridge load cells in parallel. If you use half-bridge load cells, it is common to use four and connect them so that they together create a full Wheatstone bridge.
August 09, 2019
FERNANDO MIRANDA GIMENES said:
This looks a very very nice gadget. I am definitely inclined to buy one.
Just one point that I didn’t understand is how you guys have built a full bridge using only 3 load cells? As far as I know, a full-bridge requires 4 load cells. Just wondering about the accuracy and stability of the product.
August 09, 2019