project updates

finally setup the raspberry pi.  used disk imager to write wheezy raspbian to a 16gb sd card.  still debating what awesomeness will come of this.  maybe a dropbox or pirate box?  def think raspberry pi foundation should host a diagnostic hardware hackathon: building low-cost diagnostic tools for the developing world.  low-cost compact peripherals like life support systems, refractometers, facscount systems, imaging devices, hematology analyzers, and other processor dependent diagnostic and treatment devices.  this is coming up on my list.

as for the dry aged steak freezer, it's about ready to go.  nabbed a 110V willhi digital thermostat on ebay for about $15.  you could hardwire the whole thing to your fridge, but i yoinked out the analog thermostat (red and black wires) and connected it to the digital.  also cut an extension cord to use as an external power source.  i actually drilled a hole through the fridge and remounted the thermostat outside since i think the op temp needs to be > 0 C.  however, there are a handful of ways to do this.  you can connect your thermostat directly to your compressor if you want or if you rewire your fridge so that the electricity is connected directly to your compressor instead of through the internal thermostat, you can just wire the fridge's power source to the switch (red and black wires).

anyway, while the thermostat's control accuracy is 1 degree, the whole thing is in celsius so it's less accurate (by 20 to 180%) than fahrenheit.  i dropped the hysteresis from 5 degrees to one degree.  this means the compressor kicks in when the thermostat reaches one degree above your set temp.  dry aging meat has to be in a pretty sterile and controlled environment with the temperature between 34 and 36 fahrenheit, so i'll update on what happens with this celsius business.

as you can imagine, these fridges weren't built to be this cold so the insulation isn't all that great.  the cooling cycles were about 5 minutes so i put about three gallons of water in the fridge to stabilize the temperature (water has a high specific heat = loses and gains heat slowly).  haven't remeasured cooling cycle yet.

did some testing with paperclips and scotch tape (don't ever try that at home).

also been told that laminar air flow over the meat should be about 60cfm, but have seen people dry age in stagnant air.  i have some server fans handy, but i might give this a go as is for now.

more updates and photos to follow.

next steps, getting some water softener salt to suck moisture out and finding a well marbled steak.