Wednesday, September 14, 2022

espresso machine hacks


Fancy coffee machines are extremely expensive and basic models do not offer much in the way of instrumentation. For my first foray into the coffee world, I wanted to see what was happening without spending hundreds (or thousands) on a professional coffee machine.

Good coffee starts with predicability. Pressure and temperature must be regulated accurately to extract the perfect flavors and texture for espresso.

This Delonghi pump espresso machine works well for a first machine but left me desiring more accurate temperature control and pressure feedback.


Here is the last picture first, showing the final features.  I've added a pressure gauge and temperature controller.  The pressure is mostly the same for all coffees using the built-in coffee holder but I'll be fixing that soon by moving to a bottomless portafilter.  

pump espresso machine with added temperature controller and pressure gauge


These are the stock internals of the coffee maker.  The purpose of this picture is to help me figure out how to reassemble everything and reverse engineer the wiring.  Here we can see two separate temperature controlled switches which control power input to the boiler.  One switch is for "brew" and the other is "steam".  I'll be replacing the "brew" temperature switch with an external temperature controller. 

stock boiler


Here I am working out the wiring details.  Later this will help to insert the temperature controller.  I wanted a temperature controller to perform my own (less professional) experiments with extraction temperature.  The front panel selector sends power to the stock temperature switches which are NC or Normally Closed until the desired temperature is reached, then they open and disconnect power to the boiler. 

boiler wiring


Espresso pressure is one of the most important factors in making a great cup of espresso. The pressure is created by the pump in an espresso machine and it forces hot water through the coffee grounds at a high pressure. This pressure is what extracts the coffees oils and flavors, giving espresso its signature taste.  
If the pressure is too low, the espresso will be weak and watery. If the pressure is too high, the espresso will be bitter and have a burnt taste. The perfect pressure for espresso is around 9 bars (130 psi). Fancier espresso machines have a pressure gauge to give the operator some feedback about this metric.

This machine has a spring limit setup inside the boiler which forces the pressure up to 90 psi before exiting into the coffee.  The pressure is predictable but not adjustable.   

exploring pressure gauge location


The temperature controller requires an external relay, in this case an SSR or Solid State Relay to switch on and off the boiler.  This replaces the "brew" temperature switch from the boiler.  I left the "steam" switch in place to allow an easy switch to "steam mode" from the front panel switch.  You can see the heatsink for this SSR the first picture of this post.  It turns out the heatsink is not necessary for heat dissipation. It does help hold the SSR in place and looks awesome anyway... 

added temperature control relay


A portafilter is a key part of any espresso machine. Its the part that pulls the espresso shots out of the machine. Its also where you add the beans to the machine.

The Delonghi "2 cup" filter has one tiny hole at the bottom which makes it a "pressurized" filter.  The entire contents are pressurized up to ~160psi during extraction.  As long as the coffee is not overly packed, this pressure level is reliable.  If the tiny hole clogs, the boiler pressure races above 200 psi while no coffee is coming out. 


The next steps are to add the "bottomless" portafilter and perfect the tamping technique.  With this non-pressurized portafilter, the tamped coffee grounds will more directly affect the extraction pressure.  A finely ground coffee with an accurate tamping should produce an extraction around 130psi. 

Thursday, March 11, 2021

rip sadie

Sadie passed away just before turning 13 years old.  We already miss her dearly.  She was a good dog and we have many wonderful memories with her.  



Friday, February 26, 2021

keep trying

I'm still around, making stuff.  I switched back to OpenSCAD to complicate things and because I like starting over. 

Thursday, August 20, 2020

cyberdesk: my cyberdeck inspired raspberry pi terminal

This build was inspired by movies like Blade Runner and various projects and articles featured on hackaday.  It is a desk-bound Raspberry Pi 3 and tiny monochrome crt monitor.  Salvage items such as door hinges and light switches found a new home.  A moving VESA mount adds some mobility.

Monday, November 26, 2018

Mowbot 4.0!

The last mowbot was a hack.  They all were.  The future for the mowbot is something that will hopefully last much longer.   I'm using FreeCAD to design what I hope will become the last major iteration of the mowbot frame.

mowbot isometric view
Things will be different this time... Maybe. 

Maybe a roadmap will help keep this project on track.  A timeline would probably be a good idea too.

  • better balance 
  • improved traction
  • adjustable and removable mower
  • rake attachment
  • striping bar
  • unified power system (gas engine charges main batteries or fully electric)

Wednesday, December 13, 2017

android vr still sucks

I've been anxiously awaiting decent VR tech since long before the Oculus Rift.  I had hoped that after so many years the technology would finally become usable.  The current technology is close, but it still sucks.

There are plenty of other reviews for the available VR options on Android so I will try to keep this brief.

The Google Cardboard knockoffs are probably the best bang for your buck.  They can be more comfortable than the Daydream View and benefit from the large-ish ecosystem of google cardboard apps.  My face hurt after only a few minutes of trying the Daydream so I didn't spend much time in it.  The carboard/daydream apps still suck, by the way.  If you like looking at cartoons through screen doors you might enjoy all that.

Samsung GearVR is the most comfortable headset that I've tried.  The headset fits well, keeps light out and is quite immersive.  The Oculus apps suite is still maturing and there are many experiences to choose from.  I liked this headset the most but still couldn't wear it for more than 20 minutes at a time.  And, of course, you still get the terrible "screen door" effect.  Perhaps pixel density on Android devices is still too low?

Focus is a common problem for all three headsets.  As I look to the edges of the "screens" things get blurry.  Only the center is in focus, so I have to move my head around a lot instead of just looking left or right.  For example, try reading the menu at the bottom of Oculus home without pointing your head at your crotch.

There is currently no realism in Android VR.  All apps are "low poly" or "lo fi", presumably due to processing limitations on mobile platforms.  VR on PC might be a different story today, but when the Oculus Rift Developer Kit came out it was the same thing.  The comfort and focus issues might be close to resolved but the visual quality has a long way to go.

Saturday, April 8, 2017

mowbot reboot

I'm working on rebuilding the mowbot.  One of the main problems with my previous design was that a lot of weight was placed on the front caster wheels, eventually causing them to fail.  My next iteration of the mowbot will position most of the weight over the rear drive wheels.  With less weight on the caster wheels (and perhaps sealed bearings?) they should last much longer.

The first step for the new frame is the motor mount plate.  I designed this in OpenSCAD, exported to Inkscape and finally printed on paper to use as a template.  A good friend allowed me to use his plasma cutter (thanks Chris!) to make this plate.  

Next I will start mocking up placement of the mower deck and batteries.