Replacing the Gaggia Classic Coffee Thermostat with a TSIC 306

For some time I’ve been using the DS18B20 to measure boiler temperature, but decided to upgrade to the TSIC 306 which has a wider temperature range and faster update rate.

The TSIC 306 is a fairly small TO92 package (about 4.5mm wide, 2.2mm thick and 4mm high) so I decided to try encapsulating it in an M4 hex M/4 spacer (as suggested here). This worked out pretty well, as shown below, pictured alongside the original thermostat from the Gaggia Classic.


The spacer is M4 Aluminium, 20mm high, 7mm across faces, male to female (Richco HTSA-M4-20-2, Farnell 1898535). The male thread has been filed down to about 6mm length, to match the existing thermostat.

I drilled out the female thread in the spacer with a 4.5mm bit to 15mm depth, filled with heat transfer compound and pushed the sensor deep into the spacer. The three sensor leads are individually insulated with heat shrink tubing, and more heat shrink is used to encapsulate the cable and sensor.

Aluminium has excellent thermal conductivity, and simply touching the case with a fingertip is enough to trigger an immediate change in temperature reading!

The only awkward part was fitting it into the boiler. I wasn’t able to do this in situ, but had to remove the steam wand and knob, unscrew the four allen bolts around the group to free the boiler. This allowed enough freedom to tilt and move the boiler slightly to the right, so that I could screw in the sensor by hand.

The new sensor is up and running on the machine, and I’ve left the DS18B20 installed in parallel, so I can compare performance.

9 thoughts on “Replacing the Gaggia Classic Coffee Thermostat with a TSIC 306”

    1. Hi

      The Auber and Sestos PID controller would only work with analogue sensors, such as thermocouple or RTD.
      The TSIC 306 sensor is a digital thermometer and it needs to be connected to a microprocessor of some kind (for example: Raspberry Pi, Arduino) which has the software needed to talk to the sensor, so unfortunately incompatible with the Auber/Sestos PID.

      I’m sure you could buy a PT100 RTD or thermocouple here in the UK, and drill out a bolt or suitable spacer to mount it. The larger suppliers such as RS or Farnell would have them, or you could probably source cheaper via ebay.

      Also, I just searched and was amazed to find that you can buy a complete kit on ebay including a PID controller, 40A SSR and thermocouple for less than £11 including P&P. Suspiciously cheap, but I’d be tempted to give it a shot at that bargain basement price 😉


  1. Hi,

    I also used a TSIC 306 in my Gaggia as you described. I use it together with an Arduino. It worked like a charm for about 4 months, but no I get error readings. What I have noticed is that while steaming the TSIC 306 is exposed to temperatures > 150°C. Do you know whether this can harm it?

    1. Hi Christian
      The TSIC 306 data sheet says that the operating temperature range is -50°C to +150°C (+/-3 °C of measurement limits), and those appear to be the absolute maximum ratings, so I would have to assume that temperatures in excess of 150°C could result in permanent damage. This would imply that it is probably only safe to regulate steam temperature using the TSIC, rather than using the steam thermostat which might allow very large temperature excursions (and there will probably be quite a large variability, depending on the individual thermostat).
      Best regards

    2. Hi Christian
      Having reflected on this, I should have mentioned that it could also be due to electrical interference on the wiring. In my own machine, I found that back EMF spikes from the pump caused communication errors, but adding an RC contact suppressor across the pump fixed that. Here’s the one I used:

  2. When you say:

    > I’ve left the DS18B20 installed in parallel, so I can compare performance

    Can you explain how you did this? Did you drill a threaded hole into your aluminium spacer to attach the original thermostat?

    1. Hi Paulo, I’m so sorry I missed your comment when it first came in, and have only belatedly approved it so it has showed up here (I use a spam filter, and have to manually approve new comments…)

      Anyway, it’s been about 7 years since I wrote the article above (so my memory is a little hazy), but suspect that I probably just cable tied the DS18B20 against the aluminium spacer (but honestly don’t remember!)

      Well, as I write this, I guess that I’ve been using the TSIC 306 on a daily basis for at least 7 years… so it has stood the test of time! (the DS18B20 was removed years ago, I don’t use it anymore)

Leave a Reply

Your email address will not be published. Required fields are marked *