Hello!! It's Joseph

  Which espresso machine to mod? look for those that has big empty space inside, eg Gaggia classic, or Rancilio Silvia, or Brasilia Lady. Typically these machines have existed for more than 30 years, and do not have any electronics inside. They use a single brass or aluminum boiler, controlling on/off by thermostats. The pump is typically a vibration pump steam generation by another thermostat     Kalaf gitlab and website provides the principles, code, schematic, builds, instructables. ( but not very active)    Jura hacking a Brasilia from Rhys Goodwin  gaggiaclassicmods iSPRESSO and instructable   Es(pi)presso and on home automations arduino-PID-controller-for-espresso by Ross Satchell and published on hackster   Espressuino based on arduino shu-fan   espresso-arm    heald ca pressure control in gemilai crm3605 by pierreye instructable on Saeco SIN006 Callan Bryant schneor design    gravimetric mod on home-bar...

    owner's manual service manual illustrated parts breakdown Coffee time wiki jong ken on heater wire replacement  coffeeclub99 heater mod to 1850W and repair blogs and ruten artisan software Automation mod from N Sager (aka Brewtal) this one from Evan Graham (aka evquink) and roasthacker : bean mass probe bracket on thingiverse evquink's github on bean mass probe v2   wifi temperature broadcast RaspberryPi mod from r0bin about temperature readings on HB :   unconfirmed. the thermal sensor on the heater box side is the feedback probe for controlling the temp you set. The temp read ( on the LED display) is from the exit side probe. The air temp entering the roasting chamber would then be limited to the 250 deg c max.  Remember this unit is reading air temp. Not bean temperature.  The heater side sensor seems to be type k embedded in hex screw, whereas on exhaust side, seems to be type k with metal sheath