Fabricating custom displays for a commercial coffee roaster


Roasting the perfect coffee bean is an art form. But even the most talented of roasters can use a little feedback on what’s going on with their equipment. [Ludzinc] recently helped out a friend of his by building this set of 7-segment displays to show what’s happening with this coffee roaster.

The yellow modules hiding underneath the display panel are responsible for setting the speed of the hot air blower and the rate at which the drum turns. They’re adjustable using some trimpots, but it sounds like the stock machine doesn’t give any type of speed feedback other than direct observation.

The solution was to patch into those speed controllers using the ADC of a PIC chip. They each output 0-10V, which [Ludzinc] measures via a voltage divider. After the speed is quantified the microcontroller outputs to one of the displays. Since there’s a different chip for each readout, the firmware can be custom tuned to suit the operator’s needs.

Keep this in mind if you’re still planning to build that coffee roaster out of a washing machine.


  1. me says:

    It reminds me of the control panel for the Back To The Future time machine..

  2. Hack Man says:

    Fabricating custom displays for a commercial coffee roaster if you just happen to have a waterjet laying around.

  3. Hack Man says:

    Sounds like I need to do a quick follow up post on where the buttons came from. Brace yourselves, they ain’t cheap!

    Yeah, they run ~ $30 USD each.

  4. 0xfred says:

    I was going to ask about the switches too. I’m getting them come up as £64.70 (about US$96) in the UK! They’re not that nice.

    It makes me wonder what sort of staff he employs if he needs vandal resistant switches on the machine.

  5. Rob says:

    Wouldn’t take too much to do a really wild retro version of this with magic eye tubes in place of the multi-seg displays. you’d have to have the switch for each function adjacent to the top of the tube doing the display, but you could also facricate a ring-switch with a hollow middle to accommodate the tube and a clear top dome to still allow for button pressing. Overkill, yes. But why the heck not… :-)

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