Before You Start
Chapter 0 of 10 · Read this before touching anything
This chapter doesn't involve any tools. Read it once before you begin.
What Gaggiuino actually does
Your Gaggia Classic Pro has a simple pump that pushes water through coffee at whatever pressure it happens to produce. It has a thermostat that clicks off when the boiler reaches a target temperature and clicks back on when it drops — a rough approximation of precision.
Gaggiuino replaces both of these behaviours with software control.
It does not replace the hardware. The pump, the boiler, the group head — everything stays. Gaggiuino adds a small computer board that reads the actual boiler temperature via a thermocouple, reads the actual pump pressure via a sensor, and controls both in real time.
The result is that you can tell it: "start at 3 bar for 8 seconds, ramp to 9 bar over 5 seconds, then hold at 8 bar" — and it will do exactly that, every shot.
Is this safe?
Yes, if you follow the instructions.
The Gaggia Classic Pro runs on 230V mains electricity (EU) or 120V (US). This voltage is dangerous. It does not feel dangerous until it is. The safety rules in this guide exist because people have been hurt ignoring them.
The critical safety rules are simple:
THE MACHINE MUST BE UNPLUGGED FROM THE WALL BEFORE YOU OPEN IT
This is the only rule that matters above all others.
Not switched off. Not in standby. Physically unplugged from the wall socket.
Every chapter in this guide that involves opening the machine starts with this step. It is not there for legal reasons. It is there because the internal components carry live mains voltage the moment the machine is plugged in, even before you press the power switch.
After you finish the build and plug the machine in again, treat the inside of the machine as live. Do not probe around with a screwdriver or multimeter while it is running unless you know exactly what you are doing and why.
A note about the E24 specifically
The Gaggia Classic Pro E24 has two differences from older Gaggia Classic Pro models that require extra steps during installation:
1. The power switch is monostable. The switch on an E24 springs back to the off position when you release it. This is by design (EU energy regulations). Gaggiuino needs the machine to stay on through a warmup phase. We fix this by removing one internal spring from the switch — a 5-minute operation.
2. The machine has an Eco PCB. The E24 includes a circuit board that automatically powers the machine off after 20 minutes of inactivity. We need to bypass this. It involves bridging two connector pins.
Both of these steps are covered in Chapter 4 — E24 Specific Mods with photos and clear instructions.
What you need before starting
Tools
Gather these before your first session. Having them ready matters.
Tools required:
- Phillips screwdriver, PH2 size (1×) — the one in your everyday toolkit
- Small flat-head screwdriver, 2–3mm tip (1×) — for releasing connector pins
- Digital multimeter (1×) — any cheap one works; you'll use it to verify connections
- Needle-nose pliers (1×)
- Isopropyl alcohol and cotton swabs (1×) — for cleaning the boiler mounting point
- Cable ties or velcro straps, small (4–6×) — for cable management at the end
- Good lighting — a desk lamp aimed into the machine makes a real difference
- Flat, clean work surface at least 50×50 cm
Workspace
Work at a table, not the floor. The machine will be partially disassembled and you do not want components rolling off a couch cushion.
Give yourself 2 hours minimum per session. Rushing this build causes mistakes. Mistakes cause troubleshooting. Troubleshooting takes longer than not rushing.
A word about the guide format
Each step in this guide starts with a numbered heading and a title that tells you what you're about to do. Before you do anything, read the entire step. Then do it.
If you see this:
Danger box — these cover safety-critical points. Read before acting.
Warning box — these cover things that are easy to get wrong and hard to undo.
Tip box — these make the step easier. Optional but useful.
Expert detail — click to expand
Collapsed boxes contain deeper technical context. Skip them freely unless you're curious.
Every chapter ends with a verification step. Do not skip the verification steps. They exist to catch problems before they become bigger problems.
One more thing
The Gaggiuino community is active and helpful. If you get stuck, the Gaggiuino Discord is the fastest way to get a real answer. Search before posting — most problems have been solved before.
This guide is written to get you through the full build without needing to leave it. The wiring diagram and firmware links are embedded where you need them. If you do want to go deeper on any topic, the official Gaggiuino documentation has the full technical reference.
Ready? Start with Chapter 1 — Kit Inventory.