I would be really interested in a specific gravity sensor for my BrewPi (photon). Are you getting any closer?
Really impressed with the temperature control, but would be amazing to plot the gravity by time as well - then if it slows down, perhaps a little ramp up… without opening the tub… 
I am also really interested. Is there anything as a community we could do to assist?
Hi, is there any progress with this function?
If it’s available then I’m planning on purchasing the Brew Pi!
On this site they explain how you can create a good CO2 sensor.
But the programming part is not my strong suit…
Anybody that has something rigged up yet (even experimental is fine)?
unfortunately not, it is in a drawer somewhere, waiting until I have more time to pick it up again.
Right now, mashing and controlling multiple processes have priority.
Ah, so it’s on your list to test it, but it’s low priority on the moment?
Then I know it’s coming in the near future and help me in my decision!
Hi, I also have a Beerbug but the disappointment is that the cloud data is basically theirs unless you pay a subscription.
I also find it’s a poor fit on my brewbucket (sloping sides) and it’s the one more thing I don’t do on brewday.
If it could log the data locally to the Pi… wow.
I assume that is a non no as it would involve reverse engineering the Beerbug data stream?
For what its worth, I’ll throw up my hand in support of Specific Gravity measurement. I think it would perfectly round out the fermentation control features of the Brewpi.
A couple of alternative approaches to pressure / weight sensors:
Hi all,
I’m looking forward in replacing my stc1000 setup with a brewpi, but at the moment for me the brewpi does not include enough features over the stc1000. The most important thing brewpi is missing at the moment for me is a specific gravity sensor, although replacing the braumeister controller with a brewpi would also be really awesome 
.
Anyway since the brewpi team is busy in delivering other important features to the brewpi I was wondering how hard it would be to implement this myself. I was thinking of using the cheap co2 sensor from Henielma(link from donzalmrol). I have some experience in matlab scriping and some minimal experience in python. My guess that it should not be to hard, but I can be horribly wrong:slight_smile:.
The hardest part I guess is obraining the correct formulas for the sensor, but I know Henielma a bit from the dutch homebrew scene. Maybe he is willing to share some insights.
Anyway, can anybody comment if I would pickung up more then I could chew?
What sensor were you going to base the product on?
I see some are thinking of using a CO2 sensor and estimating gravity based on CO2 density.
Were you thinking of a similar strategy or is there a more direct sensor for measuring specific gravity?
I’m going for very direct measurement: weighing a known volume in the beer.
Interesting. I’ve been talking to a physicist friend of mine. He had the idea to use a sonic burst. You’d send a burst through when you start the fermentation as an initial reading, then incrementally poll.
This can be used to determine the gravity of the solution.
edit
This came up as an alternative to weights to avoid having to put anything in the fermentation vessel.
If you are talking about the speed of sound: the effects of sugar and alcohol cancel each other out. You would need to look at the frequency dispersion at 4 MHz to be able to distinguish the effects.
That’s a good tip. I’d found this reference from 1970 http://www.ajevonline.org/content/21/1/1, but I can’t find the full pdf.
This guy from TI can go up to 4 MHz, but that’s at the top of its range: http://www.digikey.com/en/product-highlight/t/texas-instruments/tdc1000-ultrasonic-sensing-afe
They have a solution board for $75, so doesn’t seem cost prohibitive.
There is a much more recent paper called Ultrasound based measurements of sugar and ethanol concentrations in hydroalcoholic solutions.
Was there a reason you rejected ultrasound as an option? Seems that a buoyancy based method would introduce contamination concerns (and extra cleaning).
@Elco any updates on this? What would be the go to solution nowadays with BrewPi?
I did come across https://tilthydrometer.com/products/copy-of-tilt-floating-wireless-hydrometer-and-thermometer-for-brewing which looks like a good option.
Its been a few years and a new release since the last time it was ask, so here I go again 
any progress on the Specific gravity measurment front?
Lots and lots and lots of work invested in this, but we’re deploying a prototype in wine this september. I’m not entirely sure whether I can/should share images of it, so I’ll leave that up to @Elco.
Thanks for the reply. Sounds great, would be great to have an all in one option. while searching I found something similar from Germany (my home country). I guess you already know it, in the unlikely event you havent seen it yet, it may help you in any form 