Replacing the Gaggia Classic Thermostat with a DS18B20

For my Espiresso Machine, I needed to replace the stock thermostat on the Gaggia Classic with a DS18B20 (Digital Thermometer). My first attempt was pretty basic, and consisted of smearing the DS18B20 with thermal paste and using a cable tie to tether it the side of the boiler (just beneath the steam thermostat). This actually worked well in practice, but I wanted to come up with a better mounting technique.

Someone on the Gaggia Users Group forum suggested modifying this Circuit Board Standoff, which would have been perfect but unfortunately all the UK stock seem to be 7mm AF instead of 10mm AF, which wouldn’t be large enough to drill out.

Instead, I decided to make a mounting block for the sensor. I used some 10x10mm square section Aluminium bar stock, cut it down to 25mm length, drilled and countersunk a 4.5mm hole through the bar at 5mm from one end. This is designed to mount on the side of the boiler in place of the existing coffee thermostat, using an M4x0.7mm brass screw. There’s another perpendicular 6mm hole along the length of the bar, to accomodate the DS18B20 sensor (this is the waterproof version, which is encapsulated in a stainless steel tube).

The picture below shows the original thermostat (left), and the new mounting block, M4 brass screw and encapsulated DS18B20:

ds18b20_mount_vs_tstatThe 6mm hole intersects the 4.5mm hole, so that it can be filled with thermally conductive paste to ensure a good contact with the temperature sensor. The picture below shows the sensor and brass screw inserted into the block. The screw has been cut down to leave about 6mm of thread exposed, to match the existing thermostat.

ds18b20_mount_inserted

The final picture shows the sensor block mounted on the side of the boiler in place of the existing coffee thermostat (taking care not to over-tighten).

ds18b20_mount_in_situ

It was a challenge to tighten the screw in situ! Ideally I would have preferred an aluminium socket cap screw, but decided to use the materials to hand, rather than wait on another delivery 😉

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