La Marzocco Linea Mini - attach temperature display

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adli

#1: Post by adli »

Hi everyone,

Thanks for admitting me to this forum.

I've done a little hack that I assume would interest other Linea Mini owners as well. I found it frustrating that the Linea Mini does not come with a temperature display.

Inspired by Williamstown Roasters project on for a temperature gauge, I decided to to find a simplified solution (at the expense of cost of course...).

I found a device which is suitable for displaying the temperature based on the read out from the integrated temperature sensor in the Linea Mini, namely the Simex SRP-73 process meter. This display is ideal for displaying the temperature as its input volt range matches the output of the temperature sensor, and it can be programmed the match the temperature curve.

The device needs to be attached to the wiring of the temperature sensor (look for a cable pair attached to CN1 om the print board inside the machine, black cable is ground). The wires will still need to me attached to the print board.

I programmed the device according to this table, using the "user defined characteristic" setting in the device :
Setpoint   Voltage           V(n)       Value (C)
9	       5	     100,00	0
8	      2,5	     50,00	80,67
7	      2,35	     47,00	84,44
6	      2,18	     43,60	88,86
5	      2,05	     41,00	92,37
4	      1,94	     38,80	95,45
3	      1,85	     37,00	98,06
2	      1,79	     35,80	99,85
1	       0	      0,00	100
Setpoint is the 9 set points to be programmed. Voltage is the actual voltage, not used in programming. V(n) is the normalised voltage value, used for "X" value in programming. Value(C) is the temperature to be displayed (in Celsius in this example), used for "Y" value in programming. The curve will be linear between the points.

The Celsius scale can be changed to Fahrenheit if desired.

The read out should be accurate in the operating range of the machine (80-99 degrees Celsius).

Attached is a link to a short YouTube video of the device after the machine is turned on and warming up:

Cheers
Arne

flip

#2: Post by flip »

Very nice! Did you compare the reading with a SCACE by any chance?

adli (original poster)

#3: Post by adli (original poster) »

I don't have a SCACE, so I had to rely on the assumption that the read out from the thermistor is accurate.

The thermistor is plugged into the brew boiler, so I assume the values are correct for the water temperature inside the brew boiler.

If anyone in Oslo has a SCACE to lend me, I would be happy to test.

Ahmad H.

#4: Post by Ahmad H. »

Would be nice to show how you set it up. This is great if it shows the temp accurately.

adli (original poster)

#5: Post by adli (original poster) »

It is not very complicated.

You need a Simex SRP-73 and program it according to the table in my first post. Instructions for programming is in the Simex manual. You also need to program the input to be 0-5 volt and how many digits you want in the display. All according to the Simex manual.

Then you need to hook it up to the thermistor wires. You will need some wiring connected to pin 7 and 9 on the Simex from the thermistor wires. I would not cut the thermistor wires as this can change the impedance of the wires. I used something like this to connect to the thermistor wires:
https://www.walmart.com/ip/60Pcs-30-Pai ... hbdg=L1700

flip

#6: Post by flip »

Could you record a video with the temp fluctuations while pulling a shot?

Epicurus

#7: Post by Epicurus »

Love the idea of a physical temp display! I went the smart home route where it can show the current temperature and its history using a Home Assistant project. The other benefits beyond temp monitoring is integrating a lot of the control features into Homekit. Telling my LMLM to perform actions via Siri is really convenient.

La Marzocco Home Assistant Integration


adli (original poster)

#8: Post by adli (original poster) » replying to Epicurus »

The smart home hack is so cool, going to try this one!

Cheaper than buying a Simen also :)


adli (original poster)

#9: Post by adli (original poster) »

Link to YouTube clip of temperature fluctuation while pulling the shot. As you can see, the brew boiler temperature is actually increasing while pulling the shot.
flip wrote:Could you record a video with the temp fluctuations while pulling a shot?

adli (original poster)

#10: Post by adli (original poster) »

I also did a time laps of the temperature fluctuations while the machine is on idle: