Problems with the Panel Mount Connector

In Rodney Spark's design (which is still excellent), he used a 3-prong Panel Mount Connector to make the RTD probe and its 3 leads detachable.  This connector reminds me of the type of connector you would see backstage for heavy duty audio equipment.  It includes a built-in latch mechanism and was easy to solder, but gave me a problem during the Creme Brulee cook.

To be fair, the root cause of the problem was my inexperience in soldering.  I had unsheathed too much of the leads on the probe side of the connector and the bare leads were touching and not sending the correct signal.  I thought this was occurring on the side of the connector in the box, which was driving me mad.  The fix came with a bit of electrical tape wrapped around the exposed leads to insulate them and keep them apart.  Things are working fine now.

I do, however, plan to supplement this connector with 2.5mm tip-ring-ring-sleeve connector like you have on your iPhone.  This will also give me 3 leads (4 actually) and I'm thinking in a pinch I can also use the thermocouples from my Maverick or iGrill with a little creativity.

Problems with the AC fan

I wanted to include a chemistry-style magnetic stir plate function into my temperature controller.  I thought that would be beneficial in circulating the water in different containers.  Since I was designing my controller to be modular and be container-independent, I didn't want to have to rely on always using a submerged "fish tank" pump.  Particularly, I was thinking about small coolers with closed lids for this application.

My original plan of using an 110-volt AC computer fan with Neodymium magnets is not working so well.  The fan spins entirely too fast and doesn't grab the magnetic stir bar; it just causes it to dance around.  I also don't have a good way to slow the fan down and understand that changing the speed of AC motors is none too easy.

The Neodymium magnets superglued to the top of the fan with the stir bar attached.

I attached a plastic cover around the magnets because I was concerned they would become loose while spinning and centrifugal force would send them into my eyes or TV screen.  They are too strong for the motor to start spinning with a little push.

Another big issue I had was that the magnets were actually strong enough to prevent the motor from starting.  There was considerable attraction to the copper coils under the fan blade.  I think that instead of attaching the magnets directly to the top of the fan, I should have put in a wood or cork spacer.  I think that might decrease the attraction just enough to start the fan normally.

Then, I went on to Plan B.  I use a 12v DC computer fan, attached to a 12v AC/DC adapter, inside the case attached to the power inlet.  I would run a potentiometer across the circuit and control the voltage and visavis the fan speed that way.  But, then I heard that controlling a DC motor that way is also not that simple and you can burn out the potentiometer.  Hmmm.

The adventure continues...

Programming the Auber PID

The Auber PID's user interface is not very intuitive.  It has 3 different settings menus and instead of having buttons to access them, you enter in a numerical code for each.

Code 0001 takes you to most-basic settings, namely setting your desired temperature and alarm temperatures.

Code 0036 takes you to performance settings and the parameter values the controller uses for its math.

Code 0089 takes you to system setup settings, such as mode of operation and type of thermal probe connected.

Auber states in their manual, "For safety reasons, the controller parameters are divided into three groups
with different pass codes. You should only give the code to those who have
the responsibility and knowledge of how to properly change it."  And then they go ahead and plaster the codes all over the Internet.  I'm not sure if that makes the setting any "safer", or just "more annoying".

Since you can use this controller in any generic system, there's a nice auto-tune feature that calculates all the function parameters for your given system.  I'm assuming I would have very different parameters for my crock pot than if I hooked this up to a blower on a charcoal smoker.

You can also use this controller in non-PID mode just like a traditional thermostat, which would completely defeat the purpose of having the device to begin with.

I did do the auto-tune, which on my aging crock pot took over an hour and I had to set the temperature probe to the 3-wire RTD setting.  A two-wire thermistor is the default.

Sous Vide Build

An exciting day!  I'm starting the build of my sous vide temperature controller.

Back of the front face.

Front of the back face.  The center receptacle will be the controlled output.

Front of the front face.

Back of the back face.

First solder of the project.  Not bad.

Work in progress.

Wiring of the outlets.  The left-most receptacle is the power input.  The center power output is the regulated one.  The right receptacle is the non-regulated power output.  The thin red and black wires will connect to terminals 1 & 2 on the PID controller in order to power it.  The thicker red wires will connect to the terminals on the SSR, which will regulate that circuit.  Throughout my build, I used red for hot, black for neutral and green for ground.

I didn't know how to solder the connections to the plug.  My connections are sloppy and this was the most-frustrating part.

The RTD wired to the PID controller. 

Completed setup, other than the stirrer feature.  Notice the square marked for where the fan should go.

I ended up breaking the fan.  I used a 1/2" wood drill bit to hollow out a hole for the magnets to sit in.  Well, I tried to do that anyway and drilled right through the motor.  

Completed setup, using crock pot.  The crock pot is quite old and smells like burning, so I do not think it is the best test case.

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.