Sous Vide Supplies and Plan

I've started a project to build my own sous vide cooker.  The first step is to build a very accurate temperature controller to regulate a water oven.  The Internet is full of such designs, but I particularly liked the design I found from Rodney Sparks.

Effectively this is a box with regulated power outlet.  You set a desired temperature and plug a heating element (such as a crock pot) into the regulated outlet.  The temperature probe reports the actual temperature (in my case of the water the heating element is touching) and the power sent through that outlet is changed to increase or decrease the output of the heating element.  The PID controller handles all the math involved in how much and when the power should be provided and the SSR handles sending the power to the outlet.  It's a loop system.

Say I want the water in my crock pot to be 100 degrees, but it's only 90 degrees.  The temperature sensor reports that value to the PID, which tells the SSR to turn on the power to the crock pot, thus increasing the temperature of the water.  When the sensor reports 98 degrees, the PID will probably slow down the power.  It handles all that integral math for us.

There's also no reason I won't be able to use this temperature controller for projects other than sous vide; the controls are generic and can be configured for other applications.  I could use it to control an espresso maker or my smoker's temperature, for example.

I've also decided to include two additional features into my controller.  They are:

1. A non-regulated power outlet.  This is just a spare outlet.  I plan to plug in an aquarium pump to help circulate the water oven.

2. A magnetic chemistry-style stirrer.  Again, to aide in circulating the water, I'm including a fan with magnets.

The parts for my homemade sous vide cooker have been arriving.  I'm going to jot them here for reference.

Parts List:

1x PID controller, Auber SYL-1512A

1x Project box, Mouser 546-1455K1602BK

1x Power input w/ fuse, Mouser 693-6200.4115

2x Fuses, Mouser 0218015.HXP

2x Power outlet, Mouser 693-4300.0701

1x AC power cord, Mouser 552-AC30UNA-R

1x Temperature probe, RTD, Auber PT100S

1x Temperature probe connector, Auber RTDCON (Update: Not recommended, see note)

1x Solid-State Relay, Auber RS1A40D25

1x Pump

20x N48 1/4" x 1/4" cylinder Neodymium magnets

2x Magnetic stir bar

1x AC Fan

1x SPST rocker switch, RadioShack

3x rolls 14 AWG insulated stranded wire

3x rolls 20 AWG insulated stranded wire

Notice the silver connectors in the bottom-left.  I would not recommend these.  Next time, I will use a 2.5mm sub-mini "headphone" jack with the tip-ring-ring-sleeve configuration.  This is a nicer connection and still provides leads for the three wires.

Unboxing the SSR.

Unboxing the Auber PID controller.

PT100 RTD temperature probe.  Notice the 3 leads; most thermocouples have 2 and this increases accuracy.  It's difficult to see in the photo, but the entire cable is covered in clear insulation for waterproofing.

Unboxing the SSR.  It's smaller than a deck of cards, but thicker.

View of the SSR and Auber PID controller.  Note how this Auber model can accept either 3-wire RTD connectors or 2-wire thermocouple connectors.

The bottom of the SSR includes a heat sink.  I've heard they can get pretty hot.

Top view of AC fan.  I'm using this fan and placing Neodymium magnets on it to create an electric stirrer within the sous vide controller.

Side view of the AC fan.  Notice the two electrical leads on the right.

Bottom view of the fan, which will become the top in my use.

14 AWG (American Wire Gauge) stranded, insulated wire in three distinct colors.  I have no idea if this is the best wire to use.

20 AWG wire.  This is thinner than the 14 AWG used around the power supply and is easier to bend and work with.  I still don't know if this is the best wire to use.

My project box and rough layout of where each component will go.  

The front face and back face of the aluminum project box had to have holes cut for the components.  This step actually proved fairly annoying since I don't have any metalworking experience or tools.  I thought I could simply use a titanium drill bit, but that did not work.  I ended up paying $40 to a local student who was a robot-building enthusiast.  He did a good job cutting the holes.

Rocker switch.  I will only be using this to control the fan; the PID controller will be powered on if the power cord is plugged in.