The Gaspresso Propeller Project Ripping apart a coffee maker and converting it to Propane- and 12V operation, and developing a hideous control system to mimic ‘bot personality (Douglas Adams-like) I have a lone cabin up in the mountains, with no electric power other than a sunlight-charged 12v battery, and I also have a sailboat with 12v only. I love a good cup of espresso. So far I have brewed my coffee the Mocca way. Also I have a continous urge to make 'inventions' involving mechanics, electronics, and control-ics. First time I tinkered with cpu's it was with the Intel 6502 back in '83, later I have worked a lot with SCADA systems. I have hobby-level experience with lots of programming languages, ranging from Assembly, via Lisp, to C++ and Java. Unfortunately this urge has been sleeping for a number of (family father-) years. I find myself now in a situation where I life has been tough on me for a couple of years. I need some fun. Fun is indeed a major part of the project: I have many times been disappointed by the extremely boring and much too conforming messages displayed and spoken by digital devices. Imagine a car GPS instead saying "I told you to turn left did I not? - what’s your problem?", and also I was inspired by the sulky robots in Douglas Adam's Starship Express, like the LiftBot for instance. As you have probably guessed by now, I intend to be quite creative with the messages. For each message event, I will have 8 or 16 different 'moods', and select one of them at random each time. An example is: Serious mood: "Water tank empty", Insulting mood: "You're too lazy, cause the water tank has not been refilled", Too nice mood: "I like your lotion, why don't you come fill my water tank…" Suggestions are welcomed. Strategy By googling and reading, I zoomed in on the Parallax Propeller platform. It is a fantastic chip! More joy came as I investigated the SPIN language, which balances perfectly between low level and high level programming. There was no doubt in my mind: propeller was the way to go, so I took delivery of a Propeller Professional development Board.  Next step was to buy a conventional espresso machine that I could modify to run on 12V and propane. I bought a second-hand one cheap, and it was a model with a side-by-side espresso maker and coffee maker, which makes space for the gas burner that would be required for heating the water. Innovation The propane water heater took some pondering before the draft engineering document was ready (scribbles on a notepad), otherwise it should be straightforward. Also, the conversion of the impulse pump from mains power to 12VDC took some engineering and solenoid calculation.  And of course I want the machine to be much more user programmable than it's original, including options for adjusting water temp, pre-infusion time, etc. and I want to fit it with a maximum number of sensors. In this age of 'intelligent' and 'integrated' entertainment devices, maybe I will also include things such as barometric pressure, so it can also comment on the weather. Later in the process I decided to include a RFID reader so the Gaspresso could recognise who wanted coffee, and adress him or her in a personal way - also knowing what the prefered drink would be. Getting started The first thing to do was to disassemble the espresso machine without damaging too much of the casing. This was not so easy and required some swearing, in particular for the parts that were glued together. Then I threw away the parts that I did not plan to use, such as all the electronic circuitry and other parts of the coffee maker. Now I had a 'naked' espresso machine in front of me, and could start detail engineering. The empty space where the coffee pot used to be was perfect for mounting the Propane burner bottle. Getting started for real First conversion project was the impulse pump / vibration pump. It is normally operated by a solenoid coil powered by the mains, through a diode to make it pulsed DC. It needed to be rewound for 12V. I was not sure about the relative permeability of the core, but I settled for 150, and then run the calculations, using 1sq mm wire - which should give an impedance of 28 ohms at 50 Hz. I reconed that if I did not hit that, I could always play around with the driver frequency and duty cycle to find the sweet-spot of required power consumption and maximum pump throughput. My idea was to let the Propeller drive a power MOSFET to switch the 12VDC to the coil. When I had ripped off the old wiring, and rewound it with 150 turns, I hooked it up to a 12 battery and connected the coil for a fraction of a second - and sure, it went 'clank' and the pump squirted some water. The next step was to write a small program to output a frequency of 50 Hz and connect to the coil through a MOSFET. The pump operated fine, but it drew around 12A whereas I wanted it around 7A. Therefore I decided to wind on, reaching 220 turns before there was no more space. Testing again, the current was now around 5A, and with f at 40Hz and duty cycle 40/60 I found 7A. For any reader who thinks I could instead have used a small 12/220 converter, I would say it is CHEATING. Creating sparks and heat While I waited for some components to arrive, I started thinking about how to ignite the gas. First I thought about salvaging an ignition coil from a car in the scrapyard, but I didn't like the idea of this big power-hungry piece, instead I decided to use the 'pencil igniter' which is used in modern cars. In parallel with that (I do parallel processing...) I started thinking about how to make an efficient water heater coil. It had to be simple to make, and it had to pick up the heat from the gas flame efficiently. To find out how the heat distributes abowe the burner I held a sheet of paper over it for a second. The first sheet of course caught fire(!), but the second attepmt went well. The heat is fierce and concentrated. To make the coil I had a hell of a job to bend the copper tubing into a double and narrow coil. After some attempts I succeded, using a 8mm tube which I filled with fine sand before bending. From flames to hot water - safely The Propane burner will create 4kW of heat when on full blast. If this is going to end out sucessfully and not just burn all down, this heat needs to be managed carefully. I decided to put the heating coil inside a flue - a leftover from my diesel stove in my boat - and then fit the burner in the bottom and ventilation grilles at the top (the outlet of a discarded kitchen sink). Around this I made another metal cylinder, such that between them there is ample space for air to flow vertically and thus remove unwanted heat. Virtually no heat should reach the internals of the coffee machine doing it this way. This outer cylinder fits into a groove where the coffee filter holder used to sit. Background SW HW  EL HMI so far, so good Jan 20th 2012 The hardware story