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b2vn

Load cell bracket

by b2vn Oct 29, 2015
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Worked perfectly, load cells snapped in and there was plenty of clearance for strain

Hi and thanks!
I'm making a keg scale as well but made a new model in order to fasten the load cells to the plate in a different way. Posted it as a remix of this since it was largely based on your design.
My setup will be very similar to your. I'll be using four load cells connected to an HX711-amplifier. I wish that I had read your comment before ordering one since I didn't get a shielded one, oh well guess I will have to do some noise reduction via software instead :)

That is exactly what I needed. Thank you very much !

You are very wellcome :)

I too am looking to build a scale for my homebrew keg setup. Do you have additional information on how you built the scale itself?

Thanks!

Sure. There is not a lot to tell. The project is on halt until I get the bar extended (which seems to have been given a rather low priority). But I had the prototype up and running with just one scale.

For the main computer I have used an ESP8622 connected to an HX711 strain gauge amplifier. Lady Ada has a nice guide to get started with the ESP, https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/using-arduino-ide. The ESP module I have has a really bad antenna. I have about 5m range then the fridge is closed. Maybe consider one with an external antenna.

I recommend you get an amplifier with a shield (like this one http://www.ebay.com/itm/HX711-Dual-channel-24-bit-A-D-Conversion-Weighing-Sensor-Module-Metal-Shied-beus-/201331721236?hash=item2ee04e4414:g:mXcAAOSwEK9T6bSp), since it otherwise really picks up a lot of noise (from the wifi??).

The four load cells is connected in a wheatstone bridge (like this http://electronics.stackexchange.com/questions/174560/how-to-set-up-load-sensor-in-a-full-bridge-with-amplifier) to the amplifier.

The brackets from this design was then just glued under a piece of MDF and is standing on top of a laminated chipboard in the fridge. I also printed a ring to attach on the topside of the MDF, to ensure that the keg (cornelius 19l) is centered and not rubbing against the others or the side.

I remember that I read something about drift in strain gauges, unfortunately I don't remember where, but they have a lot of drift just after you load them. Therefore it was recommended for a setup like this, where you have a constant load on for a very long time, that you tare the scale 10-15 minutes after you put a new keg on.

I have not done a lot for the website yet. The "progress" bar is made with a table, something like. '

  '. This will definitely be changed... at some point in time.... maybe...

You can see a lottle more of the setup in this design: http://www.thingiverse.com/thing:1117059

Please let me know how the project turns out :)

Proto PCB enclosure
by b2vn

Ovv, forgot one detail. I drilled a rather big whole in the center of the MDF plate down through the chipboard and put a bolt through, without tightening the nut. This ensures that the MDF plate does not stay attached to the keg when I take it out of the fridge.

And MDF is not the ideal choice for something with constant load on, since it warps over time. When I make the next version I will either use plywood or aluminum.