La Marzocco Linea Mini shot timer, automatic backflushing and flow profiling mods

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by toto_ »

I'm currently working on three different mods for the Linea Mini:

1. Shot timer
2. Automatic backflushing - full chemical procedure (15s on, 30s off, 5s on / 5s off x 5, rinse, 5s on / 5s off x 10)
3. Flow profiling - using a new solenoid and needle valve

First I would like to thank shawndo and Peppersass who provided a lot of good information when I contacted them by PM about their flow profiling mods.

Mine is now almost ready. It is 100% reversible. I'm still waiting on a few fittings and a custom 3d printed part that I should receive next week to complete it. I'm currently still debating where to put it. The two easiest locations are at the pump and at the 3-way solenoid valve. Both locations have pros and cons. There is a third location (between the gicleur and the 3way) but removing the 3way is more than difficult so I'm not considering it anymore.

I can enumerate the pros and cons I talked about in private with Peppersass if someone is interested.
The flow profiling mod works independently from the other two mods. That said if I want to keep using the auto backflushing I will have to add a relay to control it too.

The short timer and automatic backflushing mods are implemented using an Arduino. I currently log the time and the backflush info in the console for debugging but I'm definitely planning on replacing that with a led/switch and/or a small lcd touchscreen. I just wanted to get it to work first.

That being said my knowledge about electronics is more than rusty to say the least. I noticed something off with the backflushing. There are 16 on/off cycles in total and for some of them (2-3 max) the pump is activated for 2-3 seconds, then stops, then starts again for the reminding of the flow.
I suppose something is not quite right in my circuit.

Would anyone with Arduino/electronic knowledge willing to help? I can provide a photo of the circuit with a more detailed explanation as well as the source code.



PS: It is now easy to add other options like programming the shot duration and potentially pre-brew/post-brew/pre-brew times once the flow profiling mod is added. I'm not necessarily going to add it though :)


#2: Post by wholemilklatte »

This sounds awesome, i'm definitely interested in learning more details and seeing some pictures. It sounds like an excellent project!

toto_ (original poster)

#3: Post by toto_ (original poster) »

So it appears the issue with the pump stopping during the backflush cycles was due to a bad wire. I changed them with better connectors and now everything is fine.
I also completely took over the main paddle microswitch to prevent (potential) conflicts between the arduino and the paddle. The LM board is a state machine and you can make it work backward if you don't reset things properly. I might just revert that though as the downside of doing that is now it is no longer possible to start a shot without the arduino.

toto_ (original poster)

#4: Post by toto_ (original poster) »

Just got the 3d printed part for the second microswitch. It needs some adjustment but overall it works pretty well for a first try.


#5: Post by nuketopia »

toto_ wrote:
Would anyone with Arduino/electronic knowledge willing to help? I can provide a photo of the circuit with a more detailed explanation as well as the source code.
Sure - post or PM if you like.

toto_ (original poster)

#6: Post by toto_ (original poster) »

I currently fully control the paddle to trigger the shot timer. The backflush can be stopped anytime by pressing the button. If it is mid cycle when it is time to rinse the blind portafilter you can use the paddle (otherwise it's "off") and once you press the button it will start the last cycle (5x5 x 10) of the backflush.

It took me a while to get the 2digit led to work as I had to read the technical doc to implement everything in the code (there is almost no standard with those components).

The next step will be to add the second microswitch, valve and solenoid in a week or two when I receive the last component. After that I will have to figure out how to make this whole thing more user friendly (lcd? box?) as it is currently just for testing.

I would also like to power it up directly from the machine. I would like to use a 12VDC supply to power the arduino and the solenoid (I can also use the 110VAC connection with SSR). There are 5VDC pins that could work with a boost converter module or the 110VAC ones with a 12VDC converter. I'd rather avoid touching the AC ones but so far I did not find any suitable 5V candidates are they all seemed to be used with for turning components on and off or have some sort of blinking.

toto_ (original poster)

#7: Post by toto_ (original poster) »

Identification of all the low voltage pins:

1 - Paddle Microswitch (+barista light) - 5V DC
2 - Power LED - 5V DC
3 - Potentiometer - 5V DC
4 - Water LED - 5V DC
5a - Pressurestat (brown, orange, green) - 2-3V AC
5b - Water Reservoir (grey, white) - 2-3V AC
6 - Group Temperature Probe - 5V DC
7 - Solid State Relay (Pump control) - 5V DC

Note quite sure what the pins near 7 are for.

The only reliable 5V DC power source is the potentiometer. Unfortunately there is not enough current for a power boost converter therefor the 5VDC source can not be used to generate 12VDC for the arduino and solenoid valve.
Afaik the board converts 120VAC to 12VDC then to 5VDC but the 12VDC source is not directly exposed.

This means that for the moment I'm going to rely on external 12VDC (or 5VDC + booster) battery and will look up at the 110VAC to 12VDC driver supply later on.


#8: Post by wholemilklatte »

Looks like you've got a great handle on the machine, this is the first i've seen the inside of a Linea Mini. I have a feeling that that other header is for pushing firmware updates.

Do you have any other pictures of the entire board, and is it easy to access? I bet you're right that there's a 12v power supply you could tap once you figure out where it's coming from.

toto_ (original poster)

#9: Post by toto_ (original poster) »

Here is a full picture of the board:

You can see two G5NB-1A-E relays. I suppose above is either a transformer or a converter. And on the left there is another relay.

One place I could put a converter is on top of the SSR that controls the pump:

An AC to 12VDC converter would fit just fine and can be plugged directly into the main power switch on the right:

That being said I'm not sure I feel terribly confident about the converter I used in that picture :D


#10: Post by wholemilklatte »

I bet Assafl or Peppersass might have some ideas. Do you know - is the voltage regulator right next "1" in your picture for 5v?