Over the weekend I decided to finally get around to building
my stir plate. I think I was inspired after reading Yeast. I knew yeast played a large role in beer’s character I guess
I was just always intimidated by starter production. I’ve been making starters
ever since my third batch of beer but I never really paid attention to exact
quantities. I essentially said to myself “even though I know it’s not perfect,
making a starter is better than not making a starter.” I had always planned on
making one. I’ve owned the cigar box that I used as the housing for almost two
years. All I needed to do was actually go to Radioshack® and buy everything
else that I needed.
I’ve seen many examples on the internet some more complex
than others. I decided to go with a simple design that I could adjust if need
be in the future.
Materials:
4 – M6 bolts 0.6mm long (adjust size to fit your box and
magnets)
Magnets (need to be strong enough to affect the stir bar)
4 - M6 nuts
Computer fan
Wire (18 gage)
Female connects
Power switch
Power adapter (cellphone cable 6-9V)
Power plug (most people just rewire the cable)
Rheostat (3W 25Ω)
Control knob
Resistor (25Ω)
Metal washer
4 - Plastic washers
Rubber washer
Tools:
Drill
Drill bits (varying on sizes depending on use)
Hot glue gun
Wire strippers
Procedure:
1) First
I started by drilling holes into my cigar box. I used a one inch drill bit for
the holes in the front that would house the switch and rheostat. Then I drilled
a hole in the back for the power adaptor along with some air holes for heat
dissipation. Finally I measured the holes on the top to mount my fan and
drilled those holes. I decided to counter sink the screws on the top so I used
a slightly larger bit and drilled half way into the top to lower the heads of
the screws.
2) I
attached the switch and rheostat to the front of the box. I needed to turn my
rheostat to the side so it would fit with the lid closed.
3) Then
I attached the power adaptor to the back of the box.
4) After
everything was attached I wired the system to test if it worked. I attached the
ground (black wires) from the fan and power switch to the power adaptor
connector. Then I attached the power (red wires) from the switch to the power
connector.
5) The
load line (green wire) to the rheostat (lower attachment on the rheostat) from
the power switch. Finally I attached the power line from the fan to the
rheostat.
6) I
plugged it in and success it works. I noticed that the fan was spinning too
fast so I decided to attach a resistor between the switch and the rheostat to
lower the incoming voltage.
7) The
resistor was attached to the load line and then to the rheostat. This time when
I tested it the fan was working better.
8) Now
that I know it works I used a hot glue gun to attach the magnets. I used a
rubber washer to attach the metal washer to the fan. It should provide some
give to the spinning magnets so the system is less ridged.
9) I
glued the magnets to the metal washer and then glued the metal washer to the
fan. The metal washer is designed to help keep some of the magnetic field from
messing with the components of the fan.
10) I
placed the plastic washers in between the cigar box and the fan to keep the
magnets as close to the top as possible without touching it. Then I bolted the
fan on.
11) Finally
I closed it up and voila! I have a stir plate.
The process was actually pretty simple. It only took me a
couple of days because I was doing it while watching the Stanly Cup finals and
I needed to pick up a resistor later and stronger magnets. In total it probably
cost me $30. It would have been cheaper if I didn’t need to spend $7 on wire and $10 on wire strippers (both of which I used to have until I left them with my boss at my first job).
