When I bought my machine, it wasn’t working and was sold as “unknown, non-working condition”. This model of espresso machine is super popular, and you can find a lot of info about how it works and how to repair every single piece of it. So, I won’t write everything again over here, but will make it easier for you and link all the resources I used. My main source of knowledge was a blog dedicated to modding and fixing the Gaggia Classic (mainly), which is absolutely great, detailed, and insightful, but available only in Polish. If you don’t speak this language, I suggest trying auto-translation, as the blog is totally worth it.

Using this set of links, you can basically repair anything you want in your Gaggia as well

• home page of the “Moja Gaggia, Moje Mody” blog
• how, where and which seals to change in your machine
• fixing/cleaning the 3-way valve
• how is the Ulka vibartion pump built and how to fix it
• how to check of the heaters of your boiler are OK
• big list of spare parts
• electric connections diagram

The post Repairing the Gaggia Classic appeared first on Tailored Cloud.

I think that in order to better understand the modding process of an espresso machine, you need to first understand how it’s working.
What I bought for my project was a roughly 20 years old Gaggia Classic, in a quite rare black Coffee version. Still, in regard to how it’s built, it’s the same as Gaggia Classic v1. What was really interesting to me, is that this machine uses no electronics at all: everything is driven directly using the AC power and switches on the front of the machine – really nice and simple solution!

How coffee is made

When a machine is turned on, it turns on both heaters integrated with the water boiler. Depending on whether the machine is in ‘coffee brewing’ mode or ‘steaming’ mode, there’s one of two thermocouples included in the circuit with the heaters (one disconnects when the boiler gets to ‘coffee brewing’ temperature, the other disconnects when it gets to a higher ‘steaming’ temperature). By default, they are internally connected (on), but when they reach a certain temperature, they break (turn off internally) the circuit and boiler heaters stop working. When the water in the boiler cools down a bit, the thermocouple switches back on and heaters start again. That way, the machine executes its first function: heating water. By the way, this process is what is causing some problems in espresso brewing: the difference between off-and-back-on temperatures (called hysteresis) of the heating circuit can be as high as 10 °C, which will already impact the taste of espresso. The PID controller we want to add will keep our temperature within 1-2 °C of the target value.

Unless you flip the brewing switch, nothing else happens. When you do, the brewing process looks like this:

• The pump starts pumping the water from the water tank to the hose that goes to the Over-Pressure Valve (OPV). The pressure of this water is roughly 15 bar.
• Next, the water goes through OPV. In general, you can have OPV in a form of a simple plastic wedge, that is pushed against the water current by a spring or a full regulated OPV. My advice: don’t even buy machines that have the simple one. Gaggia Classic v1 has a regulated OPV valve. This valve has 1 input and 2 outputs, so to speak. The water flows in and pushes internally on a spring-loaded rubber seal. If the pressure is low, the seal holds and all the water goes out through the first output, which is used to brew coffee. When the pressure of the water is high enough, the spring is compressed, the seal opens and some water gets out the 2nd overflow output of the valve. This output leads back to the water container, where there’s no resistance on the way, so there’s also no pressure buildup and any excess water can flow this way. That allows the OPV to limit the water pressure to a constant value – the one that is needed to open the overflow output. By regulating a nut within the OPV you can preload the spring as hard as needed and that way also regulate the pressure at which the overflow opens. Still, to calibrate the OPV precisely, you need to connect a pressure gauge somewhere. One option to do that is to block water output out of the coffee group using a blind sieve, then split the water hose and connect your gauge there. The other, simpler way, is to connect the pressure gauge to your normal portafilter, blocking water outflow using the gauge directly. So, here’s the 2nd step of the espresso process: setting the water pressure to a correct value, typically 9 bar.

  

• After the OPV, the water passes through a 3-way valve. In theory, this part is not really needed, but you still want to have it. The way this valve works is that it has 3 connections: from the OPV (so the water you want to brew your coffee with), one exits to the coffee group (where you want your water to go to make a coffee) and the second output to the drip tray. The 3-way valve works by enabling one or (actually xor the other of paths water can flow. When the AC power is enabled, the valve allows water to flow between OPV and the coffee group, but blocks output to the drip tray. When it’s not energized by AC, it allows the water to flow between the coffee group and the drip tray. Why is it useful? Just after finishing the brew, there’s still quite high pressure in the coffee group and your portafilter. If you remove your portafilter from the group while there’s still some pressure, droplets and bits of coffee will start flying around your kitchen! To avoid that, as soon as you turn off the water pump, also the 3-way valve is turned off and allows the extra pressure to be released to the drip tray through the 2nd path.

  

• Now we’re almost done. We have water at the right temperature and pressure, we’re protected from a mess by the 3-way valve, we can just push out the hot water from the boiler into the portafilter – it is the fresh water coming from the water tank that is pushing out the hot water from the boiler onto your coffee. So, put your ground coffee into the portafilter and let the water flow!

The post How a single boiler espresso machine works? appeared first on Tailored Cloud.

Still, I want to drop at least a short update here.

Over the last few months, I tried the projects I mentioned in the previous post. I also have a decision about when to use which:

– if you need wireless connectivity, MQTT integration and such – use the bleeding edge

– if you want the most advanced features, yet no connectivity and a very opinionated main developer – go with gaggiuino.

Still, no matter which you choose, you need an operational Gaggia machine first. I have an almost ready short entry about the best resources I found on the Internet when I was fixing mine.

The post Short espresso machine project update appeared first on Tailored Cloud.

For a few years, I was a moderately happy owner of an Ascaso Dream espresso machine and i2 mini grinder. They create a nice set and the coffee was… OK. Espresso was hit-and-miss, but mostly miss, and it always frustrated me that an espresso at a regular coffee bar, like Costa, is much better.

If my espresso quality is subpar, then what is required to get a good espresso? I started to check again what is considered important when making espresso. The non-ultimate list is:

• first and foremost, a good grinder that can get you the needed fine-grained coffee powder of uniform distribution
• precise water temperature control (and good water quality in general)
• water pressure control (should be 9 bar, at least as a start value)
• even distribution, tamping and extraction of coffee puck in the basket (this can be a hard one)
• repeatability and control over everything mentioned above.

After a long break, I got back to a polish coffee forum, where I wanted to check if someone figured out how to make better coffee using hardware I have. I learned there that one folk has basically remade his Ascaso Arc (same hardware, different case than my Dream), added an AT Mega based MCU and turned it into a beast. That started me off. I started to read about how espresso machines are made and how they work, and I found a few open source projects on GitHub, where people create a firmware for home class espresso machines. That was it – at this point, I knew what my next big hobby project is.

This blog entry starts a series of note-to-future-self entries, where I want to document where I found stuff needed to fix and make the open source espresso machine based on Gaggia Classic.

The firmware projects I found are:

• https://github.com/Zer0-bit/gaggiuino
• https://github.com/rancilio-pid/ranciliopid and its fork https://github.com/medlor/bleeding-edge-ranciliopid

The first project on the list is aimed at Gaggia Classic machine, while the second one supports a few machines, mainly Rancilio Silvia, but also Gaggia Classic. I read about the projects, compared them, checked on the features and decided to go with ‘ranciliopid’ or its fork. So, I created a plan and arranged it in stages:

• stage 0
  • buy a used Gaggia Classic
  • learn how it’s built, repair it (if needed), clean it and make nice
  • make it work as the original design intended to
  • add precision baskets, precision shower filter and an NPF (naked portafilter – it doesn’t change the taste of coffee, but allows you to better see how your extraction works and looks awesome – I always wanted to have one )
• stage 1 – add ESP32 MCU in the “full” scenario, with features including
  • digital control through relays of all the main electric components: 3-way valve, pump and heaters, and the TSIC 306 temperature sensor, which allows for:
    • very precise temperature control with PID controller (with 1 °C resolution)
    • timed shots: the machine stops after the set number of seconds
    • pre-infusion: when a brew starts, the machine first pumps water for a brief moment of time (like 2 s), then takes a short pause, then starts the actual extraction – this presoaking of coffee allows getting rid of the air trapped in between the coffee powder and should make your extraction more even
    • backflush: a cleaning mode, where brew group is first pressurized (with a blind sieve/basket attached), then expelled through the 3-way valve to the drip tray
  • add an OLED screen
  • configure MQTT integration
  • insulate the boiler of the machine to eliminate the gigantic heat loss of the naked metal boiler and speed up the heating process on start
  • add a water level sensor: to tell you when you run out of water, so you’re not surprised mid-brew
  • figure out how to place all of that in the machine, add necessary case for the electronics
• stage 2 – add scales
  • Good espresso needs to have a correct extraction ration and extraction time. Extraction ratio is the ratio between the weight of your final product – the espresso in your glass – to the weight of coffee beans used to make it. There’s no single correct value, but in general people agree that your extraction ratio should be somewhere between 2-3x (so from 10 g of freshly ground coffee powder you should get 20-30 g of espresso). As for time, the typical value is 25 s, but it also can vary between 20-30 s. So, to make your coffee right, you need to find (dial in) your grinding settings for a specific coffee to land within these ranges. The basic option is to set your brew time to a constant value, like 25 s, then change your grinding setting until you get the 2-3x extraction ratio. But to be able to tell the ratio, you have to put a scale under your espresso glass when you pull the shot. Now, the firmware that I want to use (and gaggiuino is working on it as well) has a killer feature: you can integrate a scale into your drip tray and connect it directly to the ESP32. That way, you can start making your coffee by weight: your machine will stop the extraction when you reach a certain weight of espresso and will tell you how much time that needed. This is my next stage after the basic functionality.
• stage 3 – features that need to be created and I would like to help contribute
  • Pressure profiling: this is the hot topic in espresso world (as far as I’ve seen). The idea is that you add 2 hardware elements: a water pressure sensor to check the pressure of water flowing through your coffee puck and an AC light dimmer, which you can use to cut down the power of the water pump. By cutting the power of the pump, you make the pump lower the extraction pressure. Controlling the pump using data from the pressure sensor, you can create a pressure profile of water during your extraction. Ideas that I’ve seen so far are based on linear change, so for example your brew starts at 9 atm but then falls down to 6 atm at the end of brew. Still, everything is possible – you just have to create a code that can execute that.
  • Drip tray overflow warning. Since the scale I want to integrate into my machine is actually based under the drip tray, it should be possible to get the weight of the tray when it’s almost full of water, then display a warning for me that I should empty it. Sounds simple and useful.
  • Automatic extraction rate brewing. As I explained above, you can either brew your espresso by time (for a given number of seconds) or until it reaches a certain weight (like until we get 30 g of espresso). The problem that I see with that second method is that my initial coffee powder weight might vary. I’d like to try to integrate a digital scale connected to the espresso machine’s MCU, that weights how much coffee powder has my grinder produced. Having this information in the MCU, I can stop the extraction when the ratio reaches a specific configured extraction rate, like 2,5 x.

Wrapping up

This is going to be a long project for me, but I’m actually writing this after already (almost) completing my stage 1. In this blog series, I want to save a set of “notes for my future self”, so that I have a written reference when I need to service my own machine again.

In the next few entries, I’ll try to start by explaining how an espresso machine works and how you can repair it if you have to.

The post Smart Espresso Machine – starting a new hobby project appeared first on Tailored Cloud.