New 12v Pump Controller with Temp Probes and Switched AC Power

I wanted to be able to use digital thermometers with my brew house and set off on a quest.  This was a long time in the making and I have learned a lot in the process.

For the control box, I went with this:
The internal panel was very much needed for this project, as you will see.
I went with these digital thermometers with probes:
I decided that I would make my actual temp probes modular and easily removable, so I went with these from Auber Instruments (
The sensors with the 4″ probes will go into the Boil Kettle and the HLT.  The 1.5″ probes will be used in the MLT and the Counterflow Chiller.
These assemblies come with the Quick disconnects on both sides and the XLR connectors to mount into the control box.  The options I chose are:

Sure, 12 feet is a bit long, but better than too short.  Besides, I can always shorten them.

Now I had to decide the layout of the controller.  I wanted to have:

  • All 12v connections switched
  • Two Switched AC connections
  • All digital thermometers on the same power switch
  • All external connections modular

Here is the design I came up with.  This is the front of the box:

The red circles are circular rocker switches.  These are what I used:
uxcell 10pcs Red Light ON-OFF SPST Round Rocker Switch 6A/250V 10A/125V AC – $4.10

The black/blue circles are the same push button switches that I have used before.
Ulincos® Latching Pushbutton Switch U16C2 1NO1NC SPDT ON/OFF Black Metal Shell with Blue LED Ring Suitable for 16mm Mounting Hole (Pack of 3, Blue) – $21.89 x 2

The blue rectangles are the digital thermometers.

Here is the bottom of the box.  This is where all the external connections will be made:

The XLR connections came with the Auber Instruments probes.  The DC connection were the last of the 10-pack I purchased for the first Pump Controller.  The AC Outlets are these:
The AC Input (Yes, it was cheaper to buy a 10-pack than a single) is this one:
Here is the rendering of the inside of the box.  Looks simple enough, right?
The giant rectangle in the middle is the 12v Power Supply
The other rectangles are Terminal Strips.
Now that I had it planned out, it was time to order parts.  Not listed above are:
Then the parts started coming in.  This is the part that is both exciting and frustrating.  I am excited to see everything show up, but cannot yet build it.  The Digital thermometers, AC outlets, and Cable Tie Mounts were on the slowest boat possible from China.
Here are the four thermometers when they finally arrived.  They are 12v and are perfect for this implementation.

The power lead and the probe are both respectable lengths, but will also be cut.

Notice the little jumper to the right of the thermometer here.

Remove that jumper from this hole in the back to convert the readout to Fahrenheit instead of Celsius

This is the shipment from Auber Instruments.  I was very impressed with the packaging

Each probe came in its own plastic, cushioned tube.  These are the 1.5″

And these are the 4″

Inside the bag we have the XLR connector for the box.  This connector is already pre-wired for the internal connections, too.  Note the ends on the cable.  One side has an XLR female and the other is a Quick Disconnect reminiscent of those that are standard for air compressors.


This is the TV Mount.  I wanted one that was fully articulating and was surprised by how inexpensive this one was.  (And at Home Depot, not Amazon!)

I got these from Home Depot.  The bags are $1.18 each.  These fit the nuts that came with the TV Mount.

I did have to cut the screws down so they would not touch the plate in the box.


Four holes later and the mount in on.  This was for dry-fit only.  It was removed after testing the fit.  I re-installed it prior to mounting the plate on the inside.


Here, I have mounted the 12v Power Supply and terminal strips to the panel insert.  I tried to keep in mind the space needed for the wiring when placing everything.

Once placed, I drilled holes where needed and secured everything with screws and nuts.

Checking the fit and spacing.

I then moved to the bottom of the box itself.   I covered the whole bottom with painters tape

This allowed me to measure (and remeasure) and  draw the layout I wanted


I then used a combination of spade bits (which led me to buy the step bit set), drill, and Dremel to cut out the holes.


If you look closely, the “wings” on the top outlet are shorter than those on the bottom.  These hold the outlet in place.  The control box is very thick and these needed to be cut down to fit.

Once I dry fit everything, I removed the tape and secured everything

This is the inside view with everything secured.  I placed terminals on the AC connections to ensure fit.

A close up look at the DC connections

Checking clearances with the plate set in place.

Plenty of room.  Looks good, moving on.

Now to tape the front of the box ad start laying out the template

Layout complete, it’s time to start cutting

The Dremel makes quick work of the rectangular cuts

The step bits work much better on the holes.  Nice and clean.

Test fit with a push button switch. This was replaced with a Rocker switch later

All holes cut and tape removed

Thermometers and switches installed

This is the inside of the front panel


I cut all the power leads and attached them to the terminal strips.  White wire with red terminals are positive, Black wire with blue terminals are negative.  This is the wiring scheme used throughout this build

Neat wires are happy wires!


Next, I moved on to the push button 12v switches.  I used the 0.110″ blue spade disconnects from eBay on these.  I had to squeeze them together to fit the small terminals on the switches.  If I were to do it again, I would just solder the wire directly to the switches.
The wire that I am using is a spool that I have had for years.  I used it to install camera systems and have a lot left over.

All four connected

As you can see, power input (+ and -) run from the terminal blocks to the switches and then to the 12v connectors on the bottom of the box.

Terminal block close up

12v connectors close up

Here is a view showing everything connected.  I know we skipped the AC connections, but there is a close up soon.

Here is the front panel with all connections made.  The temp probes were cut and the wires soldered to the wires coming from the XLR connectors.

Close up of the lower terminal blocks.  Note that on the three AC blocks, constant power goes to the 12v power supply.

Close up of the top terminal blocks.


Through testing, I found that the digital thermometers do NOT work with the temperature probes I purchased from Auber.  More specifically, the RTD sensor is the wrong type temperature sensor.  I tried a K-Type and that didn’t work, either.  Now the cold sweat forms.  If I can’t get this to work, then all the money spent is for not.
There is absolutely no documentation for the thermometers I bought, so I had to go into sleuth mode.  The probes that came with the thermometers were wrapped in metal.  I removed the metal and all the epoxy (carefully) to expose the end of the probe itself.  Turns out, this is a simple Thermal Resistor.
I didn’t get my hopes up, but purchased some anyway, they were cheap
It was $1.00 difference between the 50-pack and the 100-pack.  I knew I would mess a few up, so had no issue with the larger pack.
I desoldered the RTD sensor from the probe body and soldered the thermistor.  Lo and behold: IT WORKED!  whew….I could start breathing again.  Wow, what a relief!

Simply covering the thermistor with heatshrink was too thick to fit into the 1.5″ probes.  I turned to Liquid Tape as a solution.
Gardner Bender LTB-400 4-Ounce Black Liquid Electrical Tape – $5.99

I simply dipped the soldered assembly into the jar and let it dry for a few hours.

As it dries, it shrinks. It was only then that I could fit the thermistor into the probe.

I can then assemble the probe body.  I wrapped the threads with plumbers tape, about five times.

Here, you can see the 1.5″ probe installed in the Mash Tun.  To add the probe in line, I added a stainless tee and nipple.

Here, you can see the whole assembly.  I did the same to the wort output of the counterflow chiller.

I got the the tees and nipples here:
Stainless Steel 316 Cast Pipe Fitting, Tee, Class 150, 1/2″ NPT Female – $2.80 x 2
Merit Brass 4008-001-10 Stainless Steel 304/304L Pipe Fitting, Close Nipple, Schedule 40 Welded, 1/2″ NPT Male, 1-1/8″ Length (Pack of 10) – $9.00

Connecting the cable to check clearance.

Here’s the connection on the Boil Kettle


And the Hot Liquor Tank.  Yes, I labeled each of the connectors.  This way, I don’t have to trace the cables each time I use them.


I built a frame to mount the box to the side of the cabinet that holds our MLT from two 2x4s.  The wood was $2.18 each from Home Depot

The TV Mount makes it easy to move the box into any position for easy viewing

Here’s a shot of the back of the Control Box mounted

All cables connected.  Two for the pumps and three for the temp probes.  The fourth is coiled on the hook, waiting for the CFC to be used.


Brew Day finally happened!  Testing the probes prior to filling the HLT.  Note that the second sensor is reading higher than the others.  I had just installed this probe into the MLT and the heat from my hand while handling it caused the reading to jump.  One it was installed, it normalized.

Temperature sensors and hoses connected!


Overall, this was a pretty successful Brew Day.  The temperature sensors worked way beyond expectation.  The digital readouts were nice to have.  We no longer have to stoop down to read an analog dial thermometer and make sure the HLT is placed just right on the stand so we could read the thermometer and have it connected to the pump.
I had also taken this time to re-wire the pumps.  The way they were wired previously, I could not disconnect the power from the pumps to remove them from their shelf for cleaning.  I bought a pack of male and female pigtails to make the solution modular and can now easily disconnect, clean and reconnect.  Here’s a link to the pigtails:
It seemed as though I was always throwing money at this project.  I had been purchasing the parts over the course of a few months.  I have no doubt that as you have read through this, the number of links to parts that were purchased is overwhelming.
After adding everything up, I was pleasantly surprised to see the the cost was just over $500.  Half of that being the Digital Thermometers and Temperature Probes.  The total final cost of everything detailed here comes to $523.51

2 Replies to “New 12v Pump Controller with Temp Probes and Switched AC Power”

  1. Great question. I think just for the cables and probe bodies, these are still a good buy. I would definitely go this route again. They are robust and easy to connect/disconnect.

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