Measuring specific gravity with a raspberry pi

[Praetorian_TMOTC]

Hi all, I want to build a cheap method of measuring specific gravity in my home brews. Either bluetooth or wireless. There are a couple of products that do this already but all are from the US and rather pricey at around the $200 Aus mark. Seeing as I need multiples I really don't want to spend $600-800 on these. So how would one approach it DIY style? After all sorts of ideas here...

The most promising I can think of would be similar to this one 

https://www.plaato.io/

From what I can see, it measures the amount of bubbles going through the airlock with an infrared sensor and since C6H12O6 → 2 C2H5OH + 2 CO2 then this equals the approximate alcohol content. 

Issue is it's not 100% accurate and once fermentation stops, no more bubbles.

What other methods of measurement are there?

Commercial products available include:

https://tilthydrometer.com/  - The nicest looking of the bunch IMO

https://www.brewperfect.com/product/brew-perfect-wifi-digital-hydrometer/  -This might be the other way to go using a "gravity torpedo".

https://www.plaato.io/ - As above

https://www.morebeer.com/products/brew-perfect-classic.html - Formerly known as the Beer Bug (kickstarter). I actually just remembered I have one of these somewhere... 

So how would you do it?

Cheers!

[Kris]

I'm not sure but I've had success on tindie with wierd sensors.
58 for 10 of these
https://www.tindie.com/products/Ruilongmaker/analog-alcohol-sensor-mq3-for-arduino10pcs/
I reckon they would need calibration though...

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From: Praetorian_TMOTC <praetori...@gmail.com>
Sent: 8 June 2018 13:54:55 GMT+10:00
To: Robots & Dinosaurs <sydney-h...@googlegroups.com>
Subject: [RnD] Measuring specific gravity with a raspberry pi

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Sent from my Breville Talkie Toaster with K-9 Mail. Please excuse my brevity.

[Praetorian_TMOTC]

Not sure how those type of sensors could be dropped in a liquid environment...

Reading about the tilt it seems to use the angle to determine the SG... interesting..

"It makes use of a novel concept to track your gravity. It has a digital inclinometer on board, which measures how much it’s “tilt”-ed . The weight of the device makes it want to sink in your beer, and buoyancy of the cylinder counteracts it. The thicker your wort is, the Tilt doesn’t sink as much and as a result has a greater tilt. As your fermentation progresses and the gravity drops, the buoyancy decreases and Tilt sinks lower and becomes more vertical. The circuitry measuring the angle does some calculations and outputs the angle as a gravity measurement."

[Praetorian_TMOTC]

Found a couple of projects on HaD that relate... putting here for those playing at home.

https://hackaday.io/project/21386-wifi-digital-hydrometer

https://hackaday.com/2017/03/01/iot-device-pulls-its-weight-in-home-brewing/

[Praetorian_TMOTC]

FYI, I caved and bought the Tilt... :( 

I hate not having time to actually do projects.