#161 Measuring weight using an ESP32, a strain gauge, and a HX711

Let’s build a connected scale, which alarms us when the food bin is empty. Of course, we will be able to use the same principle to measure the weight of any other good like the honey in remote beehives, or even your own weight to visualize it somewhere in the cloud…
So, today we will:
- Measure quite small weights with an Arduino like Microcontroller
- We will need some tricks to do that
- Then, we will build a bowl for our cat which is capable to detect if no food is available anymore
- And we will send a Twitter alarm to our Smartphone

We will also slow down the clock rate of the ESP32 to fit the timing of the HX711chip, and will use an OLED display and an MQTT library.

Links:

Please do not try to Email me or invite me on LinkedIn. These communication channels are reserved for my main job

[williamna]

As someone who watched many YT Videos, mostly scrounging around for electronics info I am always glad to see a video addressing the topic I am looking for/interested in even if not really a "well done" video. Then came the day I stumbled on your channel and I have found myself watching other videos thinking "if Andreas had done this video I would already have my answer and a working example AND all relevant info explained in a video that isn't 45 minutes long and putting me to sleep" As always, clear and to the point as a YT video should be. Well done.

[bmoroneyau]

Thank you for your projects and for your insight into electronics. You've inspired me to not only connect and program the ESP32 successfully (just finishing my WiFi weather station) but with this latest project our cat may never go hungry again! Thanks again Andreas for producing these videos and helping inspire a new community of makers!

[Chuenthe]

Wow, this is exactly what I was looking for! I have been migrating a project to the ESP32 (using the DS18B20 temperature sensor) and it kept dropping values where the previous Arduino did not. So it's just too fast! Can't wait to try slowing down tomorrow. Also, I am a hobby beekeeper and wanted to experiment with logging the weight of my hives over the coming season (I'm in New Zealand the season is just starting). So I've got my next project lined up already! Thank you as always for the great video!

[nburton]

I've had all the parts for this project for some time and remember seeng your video. Worked a dream and like you I’am amazed at it’s accuracy. Would have never thought of slowing down the esp32, great tip. Saved me many hours of debugging.
Just got to get a cat now :)

[Emillos]

Great, and again super timing! I have a litter box alarm for our cat mishka ;) based on the door pulse. Friday a collegae suggested to measure it and I was already looking for a scale with serial connection. But of course now Mr Spiess comes along and gave a much better inspiration. Thanks!

[vivetgrosalexis]

hello, it's always a pleasure to watch your videos. they are carried out with so much pedagogy that you manage to explain the most complicated things simply. Well done. Alexis. France

[richard_wenner]

Spiess's Law 'The cost of any ADC should not exceed the cost of what it's used to measure'. I have never considered that, in the past, but now you have enunciated it - it's so obviously a fundamental law of the universe! A small gravitational wave of shock has just been released from Wales - as a consequence (did you see it on your strain gauge?.

[jasonmhite]

Great video as always. I've had a project idea to make an automatic cat feeder but kept putting it aside as I would came up with problems, one of which was how to tell how much was in the bowl. Maybe now I should go back and revisit it...

[GeekMustHave]

Thank you for showing a unique combination of technologies for solving the "Is the cat's bowl empty?" I often wondered what Node-Red could be used for now, I have a good example. You do such a good job explaining the technology bits and bobs that it makes the big picture much easier to visualize. That is a rare talent. Leep broadcasting.

[deangreenhough]

Good Morning Andreas 😀

Yet another example of something I had no apparent interest in - strain gauges.

Well, I'm sitting up and all of a sudden interested! Both my missus and my cat 🐱 have also been watching this video and I have been given a few looks suggesting it's time to build one😀

A great tutorial, I especially liked the esp32 and the issues along with your tips and tricks.

You say the ADC should not cost more than the cat😂😂😂😂

Andreas you are quiet the comedian. ✌️

Keep up the hard work my friend

[richard_wenner]

It's stunning how sensitive these gauges can be. Your, Dishka, cat pellet demo is an example of this but given the leverage effect of the bar, surely the pellet will record a different mass depending upon where in the dish it is placed. My bar, which can tolerate up to 20kgs, can currently differentiate between one and two match sticks!

[alidollar]

10:36 "as with all models she had to starve a little before her appearance" that was hilarious :D btw great video as always!

[LatinDanceVideos]

That was really cool. Special thanks for resolving the slowdown to eliminate anomolies.

[TheMrten]

absolute nice video as allways on your channel ! keep up with that high quallity videos ! thumbs up

[ziliboba]

Andreas, thank You for your videos - always very interesting and helpful!

[lioman]

great! Next level is servo motor filling the Dishka's bowl. Thank you.

[AllanKobelansky]

In your video you mentioned temperature compensation requirements. A Wheatstone bridge takes care of that. Nice job.

[rkaid]

Cool project and good explanation! Although, when i had a cat he never failed to notify me if he was hungry and his bowl was empty... lol - but of course he couldn't tweet.
Idea: Make an automatic feeder that triggers when bowl is empty and a certain amount of time has passed since it reached zero. And maybe only activate that function if the cat has to stay at home alone for a long period of time. For example: It should be possible to trigger it only if your (and your wife's) phone isn't connected to your local wifi (thus assuming that no one is home).

[klassichd]

Thanks for the great Video. I like gages and such stuff.
This kind of project is perfectly to use the "oldfashioned" ESP8266 out which are not as fast as the ESP32.

[MaxintRD]

Great video again. Thank you for your clear explanation. I hope your cat was paid well for starring in this video! Perhaps you could also weigh the cat and give it some automated laser guided exercise when overweight?