(NERD WARNING)

I always spend a few seconds adding or taking that last 1g of coffee of the puck to get a perfect weight dose. For those who brew by the numbers, it's just one of those variables which changes together with a bunch of other variables.

No matter how many times I've tried to adjust the timer on my doserless Mazzer Super Jolly, it was never consistently on target, frequently been off by 1g to 2g. Different beans, different grind settings, beans age, ambient and burr temperatures all worked together to make sure no matter what I tried, the dose in my portafilter was not to be trusted .

I first heard of the Acaia bluetooth scale while browsing coffeegeek six months back. Despite all the cool things it does (brewing data logging and broadcasting on social media), it did not control my grinder for me.

This is what I came up with

I used :
- an ARM 3 microcontroller board with a bluetooth adapter which controls a relay (which feeds the Mazzer).
- the Acaia scale to measure grind and connect to the phone.
- wrote an Android app which establishes 2 bluetooth connections, one with the scale, one with the SJSUOne board (the ARM3 board).
- Android app gets streaming weight data from scale, and outputs relay state to the SJSUOne board.

This is what is looks like. I can change beans, grind settings, at any temperature, and my grind weight remains within ...0.1g or 0.2.g (see video, sound ON and max screen please :

That's super cool!

Kurt Vonnegut defined "geek" as someone who bites the bubbles of his own bathtub farts.

I Want one of those
I Got the scale what do i need to buy and from where..?
So cool. Best summer mod ever

/Uldall

Now CSUSJ (formerly San Jose State College) is famous for at least three thing:
1 -The Bulwer-Lytton Fiction Contest www.bulwer-lytton.com/
2 - The SJSUOne
3 - And me (I graduated from there, but before there were computers that could do this that weren't the size of an auditorium).

This is incredibly cool. I wish I had the capacity to build something like this myself!

Really interesting project you have!

Is it possible for the program to "learn" the required offset by itself by calculating the rate at which the grinds are coming out?

Nice work! "Harry's Bar" is pretty cool too!

Thanks all!
I still have some work to do to stabilize the bluetooth connections. Once that's done, I may have something people can buy. It's still a prototype.

Offset :

There will be a calibration screen which runs 5g through a couple of times, and calculates the offset automatically.
I've found it to be consistent for specific beans.

For instance, the crap beans I bought to waste during development have 1g offset.

The Hayes Valley Blue Bottle has 1.5g. Just made 4 drinks this morning at 20g target, all within 0.1g to 0.2g straight onto the portafilter

Near future features will include automatic online retrieval of dose weight for specific beans (user chooses which bean is being ground, and app provides roaster recommend dose).

What is the solution for the grounds that remain in the grinder's exit chute?

I have the exact same grinder, funnel, and catch cup setup. But, I pre-weigh a single dose, drop that into a custom hopper, and sweep everything quickly, with a brush. This ensures that every shot is fresh and has one full shot weight.

If I were doing shot after shot, all day long, I could want this setup whereby each dose is weighed as it comes through the Mazzer. But, any stalling in the production process means that the grounds in the chute go stale. Maybe you just trash the extra, I dunno what I dunno.