Hot Metal Brewbot USA BOM

A coffee machine modder friend in the USA has built my rev2 board and sent me the bill of materials he used. This may give a head start to intrepid adventurers from the USA who are attempting the same.

Download it here. Note: this list was compiled before I decided that a metal oxide varistor is needed. See note 2 here.

Zinc plating

This year I have plated several parts of my coffee machine with zinc to prevent corrosion. This turns out to be surprisingly easy to do at home and I found I already had all the components I needed.

I have plated the bracket which holds the steam boiler in my Gaggia Baby Twin, the bolts which hold the boiler together and the bracket which holds the thermal fuse in place and also acts as a terminal for the earth wire onto the boiler.

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Where to mount a temperature probe?

Let’s suppose you’ve figured out a fab design for a temperature probe that could be mounted anywhere on the Gaggia boiler. What is the best placement for your probe? Two obvious considerations spring to mind:

  • Ideally the probe will reflect the water temperature well (rather than, say, always be colder than the water by some amount that is affected by ambient temperature or always hotter because it is more affected by the heating elements than the water).
  • Ideally the probe will respond very quickly to changes in temperature.

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Temperature probe design

I have not found it easy to design a cheap and reliable temperature probe which can easily be mounted on the Gaggia boiler. If you have a simple solution, I would love to hear about it.

Here I document my present probe design and an idea I have just had which is really simple and obvious to me since I built a 3D printer but wasn’t before.

There are also some notes at the end about types of devices which could be used for temperature probes and how to use them with the rev2 board.

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What to do about scale

Some time back I lived near Durham1For the sake of clarity, that’s just plain “Durham”, the ancient pilgrimage destination, rather than the Durham which always seems to have “North Carolina” appended to the name. where the water is blissfully soft. Five years of sparkly clean kettle and coffee machine that just don’t scale up! Since moving to a harder water area, I have often wanted to recapture those halcyon days. And now I think I may have…

I’ll spare you the long sob story about fruitless googling for simple effective answers to scale and jump to the solution I am now trialing: citric acid.

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References
1 For the sake of clarity, that’s just plain “Durham”, the ancient pilgrimage destination, rather than the Durham which always seems to have “North Carolina” appended to the name.

Wiring tricks for the coffee machine

When modding a coffee machine, it is easy to overlook questions around just how to connect up the wiring. The space the wiring occupies can be very hot. Just the air can easily be over 70°C and if the wire touches the boiler itself, that can be well over 100°C. Some wires also have to carry fairly large currents and mains voltage. The large currents cause extra heating and the large currents and voltages both cause electromagnetic interference.

Here are some wiring tricks I have learnt over the years. Continue reading

Mounting the flow meter

I have struggled for years to find a good way to mount the flow meter on my pimped Gaggia Baby Class. Eventually, when I bought an old Gaggia Baby Twin, I had a look a the metal bracket Gaggia uses and that immediately gave me an idea. An old PC expansion card blanking plate, bent over, a notch filed on the end and a cable tie. A little bit of silicone glue for stability and viola! Continue reading

Gaggia Baby Twin front panel protocol

I recently got (and fixed) a broken Baby Twin off ebay. I want to experiment with the extra boiler. Anyway, it turns out the Twin talks to its front panel using a TWI based protocol. Here are my notes (which I made in an ASCII editor – enjoy the ASCII graphics and sorry about the scroll bar at the bottom): Continue reading