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.

Introducing Hot Metal Brewbot

My coffee machine controller is now open source. I have uploaded the firmware and hardware design to GitHub. This meant I needed a catchy name. I have always just called my controller “coffeepid”, which is pretty generic.

After a conversation with several coffee machine modder friends (thanks guys), I settled on “Hot Metal Brewbot”.

Do you need an explanation? Right then…

It’s a (delightfully bad) pun on the hot metal printing press and an espresso press. It also describes the thing we are controlling, i.e. the boiler. And I think it sounds kind of cool.

The name was already claimed by the HoTMetaL HTML editor but that is now defunct. Searching on GitHub, there are a few random projects using the name but nothing obviously popular and nothing related to coffee. And (if you share my dry sense of humour) this gives us another justification for the name: if a programming language can be named after an island where coffee is grown and a derivative of that language can become a standard adjunct to HTML, then why can’t a coffee machine controller be named after an HTML editor?

So there.

A reflection on HRH Prince Philip’s death

I have been surprised to find myself increasingly sad at the death of Prince Philip. This may seem odd as I never met him. So why am I sad? I have been pondering this and have identified four reasons. And what can I do about the sadness? Nothing – but I believe it will pass and I will settle into a hope founded in the Easter story which is, after all, the great surrounding narrative of the week in which Prince Philip died.

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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.

Gaggia Baby Water Level Meter

One of the saddest sounds in the world is the change in tone of the water pump as the water runs dry half way through a shot. There’s no real rescuing this situation. It’s go ahead with a sub-par cup of coffee or start again. Not only is that a wasted 40p of coffee beans1For a double shot. but, worse, it dishonours the farmers, roasters and everyone else who has put so much effort into bringing such a wonderful flavour to you from the far reaches of the planet. So, what is needed is a water level meter that can warn when the reservoir is getting low. Continue reading

References
1 For a double shot.