Temperature Logging and other automation

I started thinking about temperature logging again because I remembered the Ranco ETC's have an optional analog 10V output of the temperature. While my Ranco controllers don't have this option, it occurred to me that maybe I could use my Arduino board to test some temperature logging.

My first thought was to try it with my existing temperature probes from the love controllers I have in my control panel, with the fermentor to get a nice fermentation graph over time. I have played around a bit with the probes and was able to get them to change resistance as temperature changed. I took a lot of trial and error to find the right circuit and still am not sure about what resistor is right for the dividing. Essentially what I am seeing for these probes is a 805 Ohm resistance around 30 °F and a 1.5 Kohm resistance around 175 °F. The resistance pattern seems to indicate that the probes are 2.2Kohm thermistors (manual doesn't say), which would indicate a 1K-2.2K resistor would work great. Unfortunately I don't seem to get the resolution I want. Somewhere around .5-1 point on the A2D per degree fahrenheit. Not sure if the problem is the board, A2D chip, or probe, but that resolution is a little less than desirable.

To help solve the problem I bought another board and a 10K thermistor that others have used with the board. This should help me diagnose the problem. I also went ahead and purchased two replacement sensors for the Ranco ETC's I have to use with the board. They are also 10K so should have a similar circuit and behavior. I'll provide an update when I see how these all work.

In addition to the temperature purchases I also got two more sensors to play with for other potential uses. The first is a accelerometer. My intent is to use the dynamic function of this device to detect vibration. Vibration of what, though? The idea would be to attach the sensor to the air lock on a fermentor and record the bubble rate over time based on the amount of vibration. It's just an idea, but it would be a cool way to record and monitor the progress of a fermentation when not at home.

The second new sensor with potential is a ultrasonic range finder. This is a simple device that detects how close it is to things and provides analog feedback. My initial thought was that this would be perfect as a boil over prevention mechanism. The idea being that the gas could be shut-off by triggering a solenoid when the range finder detects the liquid getting too close to the top. This would be pretty cool if it worked. Then I began to think that if this worked well enough it could also be used to detect the level of liquid in the HLT, Mash, or Boil. This would prevent the need for float switches to prevent overflow, detect levels, and even determine how much liquid has been transferred between kettles.

The last automation piece I am still working toward but is further out on my list, is a liquid propane regulation controler. Currently the methods for regulating gas would be to use a solenoid device that either turns the gas on or off. This works, but doesn't allow for fine grain control and heat maintenance. My idea is to use a stepper motor attached to a variable high pressure regulator. This would allow the computer to adjust the gas output on the burner depending on the situation by automatically turning the regulator nob using the stepper motor. Haven't done too much with this yet, just have the motor and stepper control board. Though I just put in an order for the connector that should help me wire the two together for testing.