Gene Cafe Mods

There are several modifications made to the Gene Cafe roaster for use with the Roast Genie:

  1. All of the Gene Cafe control electronics are removed.
  2. Improved temperature sensing is added to inlet and outlet plenums
  3. A triac-based heater control board is added to provide continuous power modulation to the heater.
  4. Connectors are added to allow interface to the fan motor, drum motor, thermocouple modules, and heater control board.

Outlet Temperature Measurement

The Roast Genie uses type K thermocouples in the inlet and outlet plenums of the Gene Cafe.  An earlier version of this thermocouple module is used.  The thermocouple in the outlet (pictured below) is sealed in place using high temperature RTV.




Thermocouple in Outlet Plenum


Outlet Thermocouple Placement

Inlet Temperature Measurement

The inlet plenum gets too hot for RTV so a very small notch was filed in between the two housings.  The thermocouple is sealed tightly enough in this small notch to prevent (very hot) air leaks.

InletThermocouple1Thermocouple in Inlet Plenum


Outlet Thermocouple Placement

Heater Control Board

The heater control board is based on a design I found here for another coffee roaster mod.  This basically works like a dimmer used for incandescent lighting (also used in some roaster mods).  I designed a custom printed circuit board (available for purchase here).  It is important to put this thing on a heat sink because you are controlling about 1200 watts with it.  It will get pretty hot.

I posted the schematic and theory of operation on the Arduino Sandbox site.


Heater Control Board on Heatsink


View of Triac on Heatsink

The heater control module and heatsink are mounted in the space under the original display board.  It is important to provide some ventilation for the heatsink. I will add some pictures here eventually showing how I mounted this in the roaster.


Power and communication to the Roast Genie is provided by two DB9 connectors mounted near the outlet plenum of the roaster.

DB9Connector Placement


Connector Pin-out


Connector Pin-out



4 thoughts on “Gene Cafe Mods”

  1. Hi,

    Great description in the sandbox, I am looking to make a three phase dimmer (so three of everything), bur since I am located on the other side of the atlantic we use 230V @ 50Hz, any suggestions on components that has to be changed to adapt the design to european power?

    Best regards

  2. Full disclosure here – I am a mechanical engineer so you may want to get some other perspectives as well. You should check the triac ratings – many are 400v or higher. Be sure to pick one that meets your current needs. I think frequency is a non-issue.

    As for how to make a three phase dimmer – of this I am unsure. This is where you will probably have to make the biggest changes from what I have done.

    Good luck and be careful with the line voltage.

    1. It is a type K thermocouple. You can get these from many places but Adafruit is a good source. You can also get the required thermocouple amplifier from them.

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