Temperature Monitoring with Arduino

First off, I’m sorry it’s been so long since I’ve updated anything – I’ve been pretty busy.

I’m just finishing up the nerdiest project I’ve ever undertaken.  The backstory: I’ve been unsatisfied with my bimetal thermometer for reliable measurements.  I was looking in to buying a nice digital thermometer when I found that the parts for those are ridiculously cheap.  So I decided to build my own thermometer.  But since I’m not a reasonable person, I decided that rather than have a simple digital readout, I’d like the temperature to be sent to my computer at regular intervals, so that I can track it over time. 

All of this is accomplished with the Arduino, a great little nerd toy which does most of the work for you:

It connects to a computer via USB and needs no external power.  It has a bunch of input and output pins and can be programmed to do a whole lot of things.

I decided to build three temperature sensors for monitoring fermentation temperature and one for monitoring mash temperature.  I used three thermistors (10k) and one LM34 sensor.  I placed each inside of a homemade stainless steel thermowell.  All are connected with ethernet cables, which provide a nice way to plug the sensors in to a gutted router box, which holds the Arduino:

Basically, the thermistors and LM34 alter the voltage depending upon the temperature.  They are connected to the analog input pins on the Arduino, which simply reads the voltage off of each pin and sends it over USB to the computer, and my program then interprets each voltage to obtain a temperature reading. 

Wiring of thermistor:

LM34 wired and heat-shrink wrapped:

Finished temperature sensors inside thermowells and with carboy caps (I used silicone sealant to seal everything):

… And the readout on the screen:

The readings are a bit off, because the sensors haven’t been calibrated for the ten feet of wiring.  The program is capable of using Excel’s xml format to import the temperature data directly into Excel, where I can make charts, etc.  I plan to use this on my next brew – I’ll post results!

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