# Coffee scales DIY



## cracked_bean (Apr 13, 2014)

I am thinking about making some weighing scales that I can build to fit to my machine, making them water proof practically and removing the need to remove them between shots.

Has anyone done something similar before?

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## DRAXXMENVONE (Jun 19, 2018)

I did and it didn't work! Following with interest!


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## catpuccino (Jan 5, 2019)

Scales are hard, by all accounts. That's larely why Acaia are so succesful, and why lesser companies are scrambling to copy them.

If it were me, I'd buy a Pearl and mod your drip tray something like this:

https://home.lamarzoccousa.com/product/gs3-drain-tray-mod-for-acaia-lunar-scale/


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## cracked_bean (Apr 13, 2014)

DRAXXMENVONE said:


> I did and it didn't work! Following with interest!


What was the issue?

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## cracked_bean (Apr 13, 2014)

catpuccino said:


> Scales are hard, by all accounts. That's larely why Acaia are so succesful, and why lesser companies are scrambling to copy them.
> If it were me, I'd buy a Pearl and mod your drip tray something like this:
> https://home.lamarzoccousa.com/product/gs3-drain-tray-mod-for-acaia-lunar-scale/


They might well be, but I have scales I need. It is more for fun... and you never know might add a solenoid to the group lever...

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## lhavelund (Dec 28, 2018)

I was rather taken with this set of custom scales for the Cafelat Robot (on HB): https://www.home-barista.com/levers/zeebra-cafelat-robot-extension-t61574.html

And a video of the functionality:






I guess the footprint is perfect, because of the footprint the Robot occupies. It would be difficult to squeeze into a much smaller space, I think.


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## DRAXXMENVONE (Jun 19, 2018)

cracked_bean said:


> What was the issue?
> 
> Sent from my iPhone using Tapatalk


It worked perfectly when the unit was out of the machine but aligning everything so nothing touches any part of the machine and giving an inaccurate reading was nearly impossible. I'm thinking of dismantling a cheap set of scales so the weighing mechanism is attached solely to the metal drip tray plate and the display is right out at the front.


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## cracked_bean (Apr 13, 2014)

So I made my first steps into this now. I am currently using a cheap 1kg load cell from amazon and it seems to be getting comparable results to my barista "BREWISTA SMART SCALE". The plan is to have the load cell be the only item directly under the shower screen, with cables running to the ADC then those to the uC and a screen.

My first frame was a bit too big and didn't attach in any way to the coffee machine just sat on it. My cup plate was also much bigger than it needed to be so going to lower that down to 60 mm too.

Please forgive the cleanliness of the machine I have been banging around playing with this - it is clean now - promise!






















Currently the scales have no input or output save for the screen, my plan is to have them always on through mains. Once a cup is placed the scales detect the new weight and tare, the tare weight is the one after the T: in this case the cup weighed 259.94g (ignore the last decimal place I intend to round it out). Then once it notices a gradual change in mass (like coffee pouring) it will start recording (red circle to indicate recording shot). This "recording" is really just it starting to display what is on the screen in the bar chart.


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## cracked_bean (Apr 13, 2014)

I had recorded a video but the damned coffee machine is too reflective and you get more than what you want to see 😦.


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## cracked_bean (Apr 13, 2014)

Next step has been made and I'm really happy with the results. The scales can sit on the machine and have no issues with rinsing (although it takes seconds to move them). They autodetect and tare cups, autograph and hold on screen. The accuracy still seems to be as good as my commercial scales. They sleep and turn the screen black when not in use.

Thinking about making a portafilter version now for ground coffee. 

















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## 24774 (Mar 8, 2020)

catpuccino said:


> Scales are hard, by all accounts. That's larely why Acaia are so succesful, and why lesser companies are scrambling to copy them.
> 
> If it were me, I'd buy a Pearl and mod your drip tray something like this:
> 
> https://home.lamarzoccousa.com/product/gs3-drain-tray-mod-for-acaia-lunar-scale/


 The OP being an engineering type may be able to tell us, but I thought scales are quite simplistic. James Hoffman in his comparison video said the load cell was the least complicated part. Accuracy comes into play at higher weights, but way past the 18g-20g most people care about (I'm guessing pourover uses much more, I don't know about that brew method).

Edit: Info on what scales do should anyone be interested: https://sciencing.com/calculate-microstrain-12006847.html

I think Acaia are more expensive not because of accuracy, but because of build quality, waterproofing and all the other stuff they do with the app.


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## catpuccino (Jan 5, 2019)

> 18 minutes ago, CocoLoco said:
> 
> The OP being an engineering type may be able to tell us, but I thought scales are quite simplistic. James Hoffman in his comparison video said the load cell was the least complicated part. Accuracy comes into play at higher weights, but way past the 18g-20g most people care about (I'm guessing pourover uses much more, I don't know about that brew method).
> 
> ...


 Load cells are simple sure, but as you point out it's rare that there's a combination of accuracy, build quality, waterproofing and I'd add price/value. By 'scales are hard' I meant building a product not picking a load cell off the shelf.

In my original post I'd not quite grasped that @cracked_bean wanted to tinker with something for fun. That's an excellent idea, I was more in the mindset of what was the most economical idea once you factory in time and effort - which seemed to be accomdating a proven set of scales instead of hacking soemthing together.


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## viveur (Oct 22, 2017)

I've seen a bunch of solutions:

- The fully waterproof scale, seems like the Acaia Lunar is the winner here. But they are expensive, and hence if you do break it... expensive to replace. (The "Decent" scale looks like it might be similar, and at least slightly cheaper - but hasn't been release yet.) Hard to make this yourself.

- The keep your scale out of harms way by putting it under the drip tray solution: that's what Decent Espresso offer with an adapter combined with the "Skale". Or possibly what DRAXXMENVONE suggests in their post? Depending on what specific machine you use, this could be easy to implement - not viable for my machine unfortunately

- The keep your scale out of harms way with some kind of stand between scale and coffee, but bypassing the drip tray - e.g. the ONA "stem". Fundamentally similar concept to the previous item, except that it should work with a wider range of machines? The stem is quite expensive IMHO (it does have to be sturdy though), you could probably DIY something much less elegant for less cost.

Personally I've been using a cheap AWS scale for years, and despite being dropped many times and getting wet daily, it hasn't run into issues so far (but I do need to wipe it after every session).


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## cracked_bean (Apr 13, 2014)

My background is mechanical engineering and I do work in mechatronics regularly.

For this my main concerns were something that was always on, so no batteries, and that could get wet. As others have said load cells are dead simple, a bar of known stiffness with linear deformation (I think) and then you slap a wire on the side and glue it. And distortion to the beam then has a affect on the coil and changes resistance. Ultimately if the wires are covered the load cell can get wet.

The important parts are the electronics or signal processing bits. My solution was just to move them away from the load cell, the ADC is just under the drop tray and then it has a digital signal to the controller which is on the side of the machine.

Because these maybe cost me ~£10 in parts I am happy for it to be a dedicated wet coffee sensor and don't plan on moving it.

I am actually really happy with the result and it means I can keep a constant eye on my extraction without any added hassle. If the time and mass changes I know something else is up.

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## cracked_bean (Apr 13, 2014)

I keep fiddling, this iteration the electronics are the same but I have opted for laser cut acrylic frame and display. The scales now slide back and forth on the drip tray very satisfyingly (no yaw). This now means it is 1 second to get the scales in position and use them.

Next steps I want to make a similar device for a portafilter, already have the holder made, just need to work out a nice way of showing the mass.


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## cracked_bean (Apr 13, 2014)

I have realised I have missed a crucial component of my coffee scales, they have no wifi or bluetooth connectivity. I have laid up and ordered the PCB needed for scales 2.0 IoT.


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## Blue_Cafe (Jun 22, 2020)

Great effort. I love to see this stuff.


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## Sam_d (Feb 8, 2019)

This would be amazing if it was available for purchase for the people who can't or don't want to do the mod them self. I'm guess aslong as they work well there would be a few people wanting something like this

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## siliconslave (Feb 18, 2020)

very cool - would be interesting to add a shot timer to this using the reed switch on the pump method. What board are you using for the project - arduino or something similar?


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## GlenW (Sep 7, 2013)

I've been messing around with load cells too on my La Pavoni. I use a small one I ripped out of a jewellery scale to weigh the coffee and then four bigger load cells under the machine. As it's a manual lever I can use these to derive the pressure profile.

I'm using an Arduino - was my first time doing any programming of anything since distant memories of Python at university. @cracked_bean Have you designed your own PCBs? What do they do? I'm just using HX711 load cell amplifiers connected to an Arduino - yours looks much more sophisticated!

The scales currently are just bits I found round the house screwed to each side of the load cell - need to sort something a little more pretty out.

This is the scale. The fan and temp controller stuck to the window are to cool down the group head when it overheats.









This is the graph I plot whilst making coffee: red line is pressure, green line is weight on the scale, and grey line is flow rate.









The I write it into a google spreadsheet using web hooks:









All good fun!

Next steps for me which I'll get round to at some point are:

- Nicer hardware for the scales

- Programming in the weight of the portafilter to save me having to tare the scales using the empty portafilter to record the dose

- Build a nice UX to input what grind and beans I'm using


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## DRAXXMENVONE (Jun 19, 2018)

I love this stuff. Keep up the good work!

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## GlenW (Sep 7, 2013)

DRAXXMENVONE said:


> love this stuff. Keep up the good work!
> 
> Sent from my iPhone using Tapatalk


 I'm just glad I got to something that actually works whilst I was still in the enthusiastic bit of lockdown before the apathy set in!


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## Sam_d (Feb 8, 2019)

Wow this is quite amazing for me lol this is something I have wanted to do but lack the knowledge of programming and setting out a working unit of any kind.

I'm quite interested in how this turns out for both the@cracked_bean and@GlenW I keep checking in from time to time.

Keep yo the amazing work guys

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## cracked_bean (Apr 13, 2014)

Still waiting on delivery for some of the components. It will be based on the ESP32 uC so i can have inbuilt WiFi and Bluetooth. It will give me a chance to play with iOS app development.

The PCB I showed just interfaces the uC to the HX711 and a 16x2 display. It also handles power regulation etc but other than that relatively simple. I don't have a shot timer because my coffee machine has one, but I do like the idea of hooking into my machine to determine when the pump starts.

This is actually for the ground coffee portafilter scales, but my intention after getting this one to work is to then modify the coffee scales on the machine in the same way so that it can also communicate to the portafilter scales.

I have found though that weighing every shot is really helping with the coffee. I found that i would dial in then get lazy about it and by the end of a bag the coffee wouldn't be as delicious. With the scales I am constantly aware of performance.

Regarding selling etc, once I have worked on the wet coffee scales more I could do it. Will see how they turn out.

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## cracked_bean (Apr 13, 2014)

@GlenW ; is yours an Arduino connected to a rasbpi or similar, what display is that?

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## GlenW (Sep 7, 2013)

cracked_bean said:


> @GlenW ; is yours an Arduino connected to a rasbpi or similar, what display is that?
> 
> Sent from my iPhone using Tapatalk


 It's a M5Stack - one of these . It's a ESP32 board in a nice package with a screen, 3 buttons, WiFi, BT built in, and then I program it using Arduino. You can then get different back-panels for it, and I've put on one with a bit more space which has a proto-board and I can squeeze my 2 load cells amplifiers inside so it's all neatly contained in one box. So far as my first experience with this kind of thing - really like it. The screen is high enough resolution to be useful, and its nice having a few buttons there so you can use them to tare etc.


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## siliconslave (Feb 18, 2020)

I was having a look at these the other day, seem like a nice, compact offering with a decent amount of stuff built in (or attachable). As much as the small ESP8266 boards and screen are temping i don't have a 3d printer for a case...


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## cracked_bean (Apr 13, 2014)

@GlenW ; thanks, that's an interesting product. Might look to buy one.

Currently only using a nano so the screen i have got updates very slowly. When i move to the esp32 I expect i shall be able to write it much quicker and move to something bigger and better.

My smd pots came today.. did not quite expect the size. Will be a soldering challenge!

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## DavecUK (Aug 6, 2013)

.


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## cracked_bean (Apr 13, 2014)

Due to an unfortunate event which involved rust where it should not be I had my V open. I attached a cable to the lever microswitch. Through an optocoupler and a little bit of rewiring I have my auto scales turning on with the machine. The latest version also uses a new PCB and uploads the data to the cloud!


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## cracked_bean (Apr 13, 2014)

The finished board. I just need to make a new housing for the screen and it will be complete! A lot of headaches with the HX711 I really wish I could find an i2c alternative!


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## Rincewind (Aug 25, 2020)

I can't believe i haven't stumbled across this thread until now....this is the 🐕's ⚽'s .....this module is also new to me....you do know i'll be up all night now doing some more homework lol.

What's on the end of your sense ? the opto-coupler or the micro-switch (i assume the opto for isolation ?) or the cell amp ?

Shame (as you said) that there is no i2C equivalent...i'll be goooogling like mad later.

I'm beginning to regret selling all my Pace re-work stuff now....my eyesight is getting worse the older i get...fixable with glasses (and the Pace microscope); but the main thing is that with increasing old age my "steadiness" is not what it used to be....ergo the older i get the harder SMD/SMT becomes...ah well.

I did (admin must've deleted them/post) have some pics showing the inside setup of a set of Timemore Black Mirror scales that i dismantled upon them arriving from China (was curious as to wether these were the "dearer version"; enabled via solder-pad/other or not) and the load cell arangement looked identical to yours IIRC,,,can't find pics; must've deleted them....i recall it was a 2Kg cell.

Good luck matey....i shall be watching closely.....goes into kitchen n whips drip tray out for scrutiny 😉


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## cracked_bean (Apr 13, 2014)

Before using this board I was using a nano that didn't seem to care about the grounds being tied together so all it was previously was a voltage divider to bring 24v to 3v. However the ESP32 module is a bit sensitive to these things (likely because I designed the board with no filtering on power lines really). So then I went to ebay and got a £4 optocoupler board. So that sense line goes to the optocoupler board which is connected to the handle microswitch which the gicar unit supplies 24V signal to (which is pulled to ground once pulled).

I am benefitting a lot by working from home and have access to works tools to do this work, although I am not sure if you are aware but now PCB manufacture including assembly is very cheap (although the soldering is fun for me).

The HX711 chip seems to be the defacto standard for load cells. I honestly have a cell like this.

As both of my portafilter scales and my coffee scales are based on this ESP32 module they are both connecting to the wifi and using MQTT to store the data. You can see my last coffee pour was 19.42 g in, 40.15 g out in 37.7 s. I intend to add some history to this so I can see when the beans in the hopper decrease to a level to affect grind, and that I can keep track of my consumption and know when to order more!


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## Rincewind (Aug 25, 2020)

cracked_bean said:


> I am benefitting a lot by working from home and have access to works tools to do this work, although I am not sure if you are aware but now PCB manufacture including assembly is very cheap (although the soldering is fun for me).
> 
> The HX711 chip seems to be the defacto standard for load cells. I honestly have a cell like this.


 Yeah matey, well aware; the company (can't remember name) that the College (my last employer) used manufacurered our boards for us dirt cheap; this was more economical especially on "multi-layered" PCB's....and their turn-around was quick iirc. We didn't opt for component assembly as the students were always encouraged to populate their own boards (went towards the/my assessment process as well).

Same cell in my Timemore scales.


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