Now that we're seeing those 12 volt camper coolers turning up at garage sales and thrift stores (I found one for $2.50), here's a neat little idea for turning it into a customizable mini-fridge powered by a USB port!
Step 1: Taking out the Peltier/Heatsink Unit
You'll basically just need a phillips head screwdriver and thin
socket or needlenose pliers to take apart the heatsink and fans, which
will allow you to remove the unit from the cooler. Now, you might ask
why you'd want to do this and not just use the cooler. The answer is
because most of the time when you find one of these the case will be
cracked and the cord is missing, but that's not a problem...
Step 2: The Peltier unit and Clean Up
Sandwiched in between the heatsinks, you'll find the Peltier unit,
which loks about the same size and thickness as a computer CPU. In
between the top and bottom layer, you'll see the special substrates that
have the unique properties that make the Peltier unit cool on one side
while heating the other when an electrical current is applied. There
will, in some cases, be spray foam insulation in between the two
heatsinks, which is very easily broken away with just your fingers. You
can safely remove the peltier unit from the other heatsink, as it will
be held only by thermal compound. Once you've cleaned up the top and
bottom heatsinks, place the peltier back in between the two heatsinks
and retighten the bolts. If you have any thermal paste left over from
putting together your own PC, you can optionally clean the old paste
away and reapply new paste to each heatsink just as you would on a CPU
heatsink/fan assembly before attaching it to a CPU.
Step 3: Attch a USB Cable
Peltier units are designed to operate at a voltage between 3-12
volts, and the 5 volts from your USB port work just fine. Although the
amperage could ideally be higher, the 500 mw output is acceptable. Cut
away the end of an old USB cable (or pick up a cheapy) and strip back a
couple of inches of the plastic covering. Inside you will find 4 wires,
usually within a braided or thin aluminum shield. The wire colors will
be white, green, red, and black. Trim back the white and green wires,
strip off a small bit of the black and red wires, and solder them to the
red and black wires of the peltier unit. Wrap with electrical tape or
use heatshrink tubing. If you need information on correct soldering
procedure or the use of heatshrink tubing, there are many excellent
Instructables that will gve you all the information you need, simply do a
search!
Optionally, you can attach a 1K limiting resister in between the red and black wires, although you are quite safe at the voltage and mA to not really need one.
Now, plug in your USB cable to a USB port on your PC, and within about 30 seconds you will be able to feel one heatsink become very cool while the other becomes warm. Note which heatsink becomes cool, as that's what we'll want to encase inside the mini fridge.
Optionally, you can attach a 1K limiting resister in between the red and black wires, although you are quite safe at the voltage and mA to not really need one.
Now, plug in your USB cable to a USB port on your PC, and within about 30 seconds you will be able to feel one heatsink become very cool while the other becomes warm. Note which heatsink becomes cool, as that's what we'll want to encase inside the mini fridge.
Step 4: Building the Fridge!
I used foamboard because of its ease in cutting with an xacto
knife and its insular properties, and basically built a box around the
heatsink using a hot glue gun to attach the sides and top, and then ran a
line of hot glue along the seams to ensure an airtight compartment. The
bottom piece is cut into two halves, with a square section cut out in
the center to make room for the peltier unit. I then glued the two
halves to the underside of the cooling heatsink, then glued the left,
back, and right sides of the fridge, and finally the top. See the
diagram below:
Step 5: Final Assembly and Extra Touches
I used white plastic tape to hinge the door, although you could
certainly use small hinges from a hardware store and simply glue them
into place with the door fit into the front for proper opening and
closing. I glued small lengths of foamboard inside the fridge assembly
and then glued cut pieces of a flexible refridgerator magnet on both the
inside of the door and the foamboard lengths to make a magnetic "catch"
to hold the door closed. I also threw in a battery powered White LED
and used a leaf switch to turn the light on when the door was open. I
ran the wiring of the leaf switch along the inside and through a small
hole in the back to attach to the AA battery holder glued to the outside
back of the fridge, then used white plastic tape along the wire run,
attaching it to the interior side.
For the handle I used a cheap hardware store drawer pull.
As you can see by the door, I wanted this to look like a store "cooler" that you see for drinks, so I cut a window and hot glued a section of plexiglass in the window.
For the handle I used a cheap hardware store drawer pull.
As you can see by the door, I wanted this to look like a store "cooler" that you see for drinks, so I cut a window and hot glued a section of plexiglass in the window.
Step 6: The Final Result
As you can see by the pictures, this cooler will hold a large
bottled water, or a tall 20 oz plastic soda bottle, although my drink of
choice is a Starbucks Vanilla Frappucino! The cooler will keep drinks
at about 45-50 degrees and works best when your drink is already cold
for obvious reasons. Optionally, you could use a 1 amp 7.5 volt DC
adapter, which will lower the temperature significantly without making
the lower heatsink too hot for placement on regular surfaces. In this
instance, I would strongly recommend that you add the 1K limiting
resistor in order to keep the DC adapter from becoming hot.
Step 7: Tricking it out!
Now, add graphics from your favorite game or website and make your mini-fridge a one of a kind creation. I printed out on a sheet of inkjet transparency film to create the see through graphics you see here. Have fun, and watch the video for the nice ending... ;)
