AVR controlled espresso machine

Description

I have this old Isomac Brio espresso machine. I bought the machine many years ago, and I ended up chosing this model mainly because of the built-in grinder. I have never been really satisfied with it, as it is pretty hard to get any consistent results from it.

What started out as a simple descaling task ended up being a full-blown electronic project instead...

Details

The final version of the firmware has the following features:

Configurable brew and steam temperature
Configurable grinder timer
Audible beep when temperature for selected mode is reached
Auto-flush when switching from steam to brew
Grinder-only mode with heater disabled
Config stored in EEPROM
Auto descaling mode

(Let me know if anyone are interested in the firmware source and I will upload it.)

Components

1 × ATmega32 Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontrollers

1 × 16 x 2 blue LCD display

1 × LM35 temp sensor in TO-220 package

Project Logs

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Building the controller
Tobias Rathje • 02/01/2016 at 11:38 • 0 comments

After I had a working prototype on breadboard the final controller was built into a small plastic project box:
with a female D-Sub connector to match the connector on the machine:
The final result with blue LCD and four buttons:
Yeah, I know, it's pretty ugly and it definately won't win any design prizes, but it works :-)
Controller prototype
Tobias Rathje • 02/01/2016 at 11:27 • 0 comments

The first prototype was built on breadboard:
The software was written in C using Eclipse C/C++ and AVR-GCC plugin.
Modifying the machine
Tobias Rathje • 02/01/2016 at 10:46 • 0 comments

While comtemplating what to do with the machine I stumbled upon this post:
http://coffeegeek.com/forums/espresso/machinemods/522994
It seems like this machine wasn't really optimally designed from the beginning. By adjusting the existing over-pressure valve I managed to get much better results from the machine.
But still those crummy mechanical bimetal thermostats were annoying me, and I needed some automation.
At first I used a couple of cheap industrial timers and a PID controller along with some solid-state relays to control the pump, grinder motor and heater, but they were clumsy and impractical so I decided to modify the machine for an external MCU-based controller.
I kept the solid-state relays, replaced the PID sensor with a LM35T and connected the appropriate wires to a D-Sub 9 connector on the front panel instead of the original switches.
After testing that everything was working using the connector, I was ready to move on to building the controller...