Home made liquid temperature sensor for my kegerator. 

From Liquid Therm for Kegerator

Picasa Album for the impatient: https://picasaweb.google.com/102208654018184678210/LiquidThermForKegerator?authuser=0&feat=directlink

Project: Modify an existing digital sensor to take a "close to liquid" temperature to get a more accurate reading of actual keg temperature. 

Requirements: 

  •  Simple to build (mostly stuff I had around the house)
  • Minimal tools required
  • Minimal time and effort required
  • Cheap and effective
  • *Bonus: Looks neat ;) 

Tools: 

  • 3/4" Hole Saw that can cut thin/soft metal and plastic.
  • Hand held blow torch (With Flux, Steel wool and solder)
  • Hot glue gun. 
  • Misc. Drill Bits. 
  • Safety Gear! (Safety glasses and a set of leather gloves)

Materials required: 

  • About 8" of 3/4" copper tube. 
  • Two 3/4" Copper end caps.
  • One-Wire Digital temperature sensor /w connecting wire. Here is where I got mine: DF-robot
  • Sealing Water bottle, Mine came from K-Mart for about $3.00
  • 4" hose clamp, Found at Ace-Hardware for about $2.00
  • The cheapest vodka or 99% alcohol you can get (not for drinking, the alcohol wont freeze!)

Lets Get Started: 

  • First thing is to use the steel wool to scuff up one end of the copper tube. Also scuff the inside of one of your end caps. 
  • Next, apply flux to the end of the copper tube and the inside of end cap you just scuffed up. 
  • Make sure you are in a very well ventilated area for the upcoming part. 
  • Make sure you have your gloves and safety glasses on for this part or its going to get very hot very fast!
  • Push the end cap onto your copper tube. 
  • Evenly heat up the tube and end cap by turning the copper tube over the flame of your blowtorch (You don't want to be right up against it or you may scorch the metal). 
  • Carefully apply solder around the joint of the end-cap and the copper tube until it appears to evenly seal the gap around the entire tube. This can take practice. You don't have to make it perfect it just has to be water tight. 
From
  • While we wait for the copper tube to cool off we will get started with the bottle modifications. 
  • Attach your 3/4" hole saw to  your drill and mark the very center of your bottle cap. 
  • Carefully drill through the cap. If you do this too quickly you will get a jagged hole that will be harder to work with later. 
From Liquid Therm for Kegerator
  • Next attach a soft-metal drill bit and drill a hole in the center of your second end cap.
  • Feed the wire for the temperature sensor through the hole in the end cap and attach it to the sensor. 
  • Use your hot glue gun to seael the hole that the wires are passing through. 
From Liquid Therm for Kegerator
  • Pass the copper tube through the hole in the bottle lid. I left just over 1" above the top of the bottle. 
  • The sensor is exactly the right size to pass down the very center of the copper tube. 
  • Pass the sensor down the copper tube until its near the bottom of the tube. 
  • Fix the cap with the whole through it to the top of the tube. 
From Liquid Therm for Kegerator
  • Use a small amount of hot glue to seal the seam of the upper end-cap and the copper tube. 
  • From the inside of the bottle lid, seal the area around the copper tube with hot glue. Hold the tube and the lid to make sure the glue sets with the tube at the center with a 90 degree angle. 
From Liquid Therm for Kegerator
  • Once the glue dries, use a small amount of hot glue on the top of the lid just to be extra sure the seal will hold. 
  • When everything is dried we can fill up the bottle with our liquid and toss it into the keggerator so it can chill off and we can start taking measurements! 
From Liquid Therm for Kegerator

 

I will update this in a few weeks once ive been able to gature some graphed temperature data.