When a good PID controller mod goes bad

Ever built something cool that stopped working one day out of the blue? Such was the case with my modified espresso machine.

My current machine is a Rancilio Silvia with a custom PID* controller mod. My design is similar to this one. The modified Silvia served me well every day for the past few years until one day recently. Suddenly it didn’t want to make espresso anymore, it only produced steam. The steam switch wasn’t flipped or broken, and the PID light wasn’t flashing with the machine’s boiler light.

Uh oh.

So what went wrong? Why had my espresso machine turned into a milk frother?

I unscrewed (and unplugged) the machine to find out. Once it cooled down I went over each wire with the multimeter to see if there were any bad connections or short circuits. In spite of some crumbling plastic connectors there was nothing out of the ordinary. The switches all seemed to work as well.

There’s various wiring diagrams online, so I double checked them and noticed something odd; there was a solid state relay I’d missed. When I modified my machine, I’d hid the relay just behind the front panel.

Turns out the relay was the culprit. A quick replacement and I was back in business!

There’s something to be said for taking the time to fix things yourself. A new espresso machine can cost hundreds of dollars. A new espresso machine with a PID controller is significantly more.

The new relay was forty bucks.

(* For those wondering, PID stands for “Proportional Integral Derivative.” Still lost? It’s a little computer that stabilizes something, in this case boiler temperature. With the Silvia’s stock thermostat boiler temperature varies quite a bit — unless you time it just right, the espresso isn’t great. But with the PID controller it’s a perfect shot just about every time. I highly recommend it.)

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