Corny Scales

[531Man]

Sensors connected and working - next step is to calibrate and run some tests

View attachment 56033 View attachment 56035

Very neat.
What of the underside does it rest on?
Is it those sensors' nipples?
Do they protrude further than the output board?
A serious question, but I couldn't resist the prurience of the enquiry.

 

[The-Engineer-That-Brews]

Very neat.
What of the underside does it rest on?
Is it those sensors' nipples?
Do they protrude further than the output board?
A serious question, but I couldn't resist the prurience of the enquiry.

Heh - yes the top plate, that I've yet to make, will rest on the contact points of the load cells giving about 3mm clearance versus the top of the output board.
For testing purposes I'm just using the whole thing upside down on the desk :-)

 

[The-Engineer-That-Brews]

OK - calibration done and testing underway.
Accuracy of the readings looks good. The standard deviation is about 15g, implying that about 95% of the samples should be within ±30g of the mean.
I am currently checking the creep when loaded with a full Corny :-)

5 hours later....

10 - 16 hours later....

 

[Stevieboy]

Am I right in thinking then, that if you pulled a pint, you'd be looking at a 568g lower reading? (give or take)

 

[The-Engineer-That-Brews]

Am I right in thinking then, that if you pulled a pint, you'd be looking at a 568g lower reading? (give or take)

Yep something like that. Strictly speaking it'll be a bit more because the SG is about 1.010 but it'll be near enough.
Mind you when I serve myself a beer from the corny it's rarely a full pint and tends to be in whatever glass I've got to hand - which is why paper and pen recording methods aren't going to work.

 

[Stevieboy]

What would be the difference in weight of a pint of water at 1.000 and pint of beer at 1.010? Must be miniscule..

 

[Stevieboy]

I suppose - 568 x 1.010 = 573.68grams ?

 

[The-Engineer-That-Brews]

What would be the difference in weight of a pint of water at 1.000 and pint of beer at 1.010? Must be miniscule..

about 1% more

 

[Stevieboy]

So THAT'S why I get tired drinking!!

 

[The-Engineer-That-Brews]

So THAT'S why I get tired drinking!!

Exactly mate - little-known fact ;-)

 

[The-Engineer-That-Brews]

The good news is that the creep looks to be much less of a problem than I feared.
Over the course of a day it built up to about 30g but the effect with these steel load cells is definitiely less than with the cheap aluminium ones.
It's there though, and may still be worth compensating out in software.

Creep versus time, 22kg load

 

[The-Engineer-That-Brews]

Collecting some RO for tomorrows brew and thinking maybe that could be another use-case for the scales: auto shut off the mains supply to the RO system when enough has been collected.
I know some systems do come with a ballcock arrangement but mine didn't and this would probably be less faff (for me)

All you'd need is a solenoid valve on the inlet

 

[Buffers brewery]

I like projects that have "spin off" opportunities

 

[Regfixit]

I've got an old Wii balance board that I'm looking to convert into a set of scales, hopefully just connecting to my iPhone via Bluetooth. Would be useful on brew days as they could sit happily under my boiler, would make water measurements a load easier, especially the sparge.

This uses a Wii balance board