Dual Stir Plate

I had a double brew day coming up and needed a way to do two yeast starters at the same time.  I didn’t want to build another single stir plate, I knew we would be doing high gravity beers and if we wanted to get a partigyle batch off it, then we would need 2 starters going.

I also wanted to make this one look a bit better, too.  Here is the equipment list I put together:

Cigar Box (eBay) $16.90

Amazon:
Push Button Switch – $7.16 x 2
12V 10A Pulse Width Modulator (PWM) – $9.97 x 2
1″ x 5/16″ Spinbar – $5.80 x 2
2000ml Erlenmeyer Flask – $22.92

Home Depot:
8-32 x 2 inch Flat Head machine screw 4-pack – $1.18 x 2
8-32 Zinc plated nut 12-pack – $1.18

Total cost:  $48.03

Of course, I used the DC Jack from the Pump Controller build (I bought a 10 pack) and the wiring left over from the Pump Controller, too.  The two 120mm fans came from a decommissioned PC.  Since I went with larger fans for this build, I also chose to go with a longer spinbar.  The longer bar ended up being $0.60 cheaper.

This is the Cigar Box I chose.  This is the most personal decision for the whole build, so choose one that demands your attention as soon as you see it.  I got lucky that the dimensions for the box were big enough for what I had in mind.

The inside of the box is just as nice:

I then placed the parts in the box to work out the spacing of everything.  I decided to have all my controls off to one side.

With then fans where I wanted them, I used a small phillips head screwdriver to mark the locations for drilling:

With the locations marked, the parts are removed from the box and the holes are drilled.

Since I am using flat head machine screws, I countersunk the holes ever so carefully.

In testing the screw length, the box would not close with the screws in place.  Time for the Dremel.  I took about 1/4″ off the screw, as shown in the picture.

I then marked the location for the DC Jack in the back of the box and drilled the hole for it.

Moving to the front, I drilled the holes for the push button switches and PWM knobs. As you can see in this picture, I did not have a clamp on the box when drilling the first hole for the switch and the box started to split.  I put a clamp on and finished drilling.  I then added a generous amount of wood glue and let it dry before moving on.

Note that I used a 5/8″ Spade bit to countersink the holes for the PWM knobs, as their shafts were not quite long enough.

With all the holes drilled, I created a “Y” connector in the wire to go from the DC Jack to the switches.

Wired up the switches using the same wiring diagram from the Pump Controller :

And soldered the connection to the DC Jack.

Next, I passed the PWM Control Knobs through their holes and secured them using the nut that came with them.  The reason I chose to go with the PWM that uses knobs on a wire lead is that is gives extra flexibility in the placement of the knob versus a forced placement hanging off a PCB.

Here is a shot of the wiring.  Note the heat shrink on the wire coming from the DC Jack.  That is the connection I made to create the “Y”.

Next the PCB for the PWM are placed and the switches and fans are wired in.

Here is how the front looks before placing the black caps onto the knobs.

I used the same fender washers and rare earth magnets from the previous stir plate.  Since I bought a 10 pack of magnets, there was no cost for this project.

REMEMBER:  Neat wires are Happy wires.

The  fans, THEY SPIN!!

Gotta have a shot of the switches lit up.

Closer shot of the one above.

Testing the spinbar

On low the vortex is fat, but moving very quickly.

With the knob all the way up, the vortex thins out and reaches down to the spinbar (this picture doesn’t show it, but it does).

My two starters for my double brew day.

Oh, Happy Day!

There you have it.  A dual stirplate for less than what you can buy a single stirplate.  It just doesn’t get much better than that!

Now Brew More Beer!