Defrosting My Food (Part Three)

Okay, so I realized that using an old power supply unit was a good idea (see Part Two). However, it is also loud because the fan echoes around pretty badly inside this empty metal box.

The second problem I discovered was that not all plastic storage containers are created equal. I tried to defrost some frozen spaghetti on top of this unit, but the bottom of the plastic container does not have a flat surface where the frozen part will not make full contact with the top of this box. The solution was to put another aluminum heat-sink between the inner bottom surface of the container and rest the other half on the top of the PS warmer.

This seemed like too much fuss and making the defroster device was just too dangerous if I was forced to make more (for family or friends). My odds might be really good that I would eventually get hurt gutting the dangerous components out of the inside of the power supply. This also leaves a lot of waste still.

So, I decided to make the whole unit smaller by eliminating the PS box completely.

Why not just use the heat-sink and fan by itself ? Small enough to still fit under a plastic container, even with an indented bottom. And much quieter.

The unit in the photo above was made by a friend of mine from a concept drawing I gave him. We hadn't quite worked all the bugs out of the idea yet but this was much less complicated. He rigged his to work on a 9 volt battery and power switch. We found this design much quieter, more portable and more efficient overall.

Knowing that the look of the above prototype wouldn't win points with my wife (I don't want that thing in my kitchen!), I knew it needed to be refined again. Plus, the battery would probably not last long enough to actually do the job required.

So, one more design refinement and we had a nice looking unit that runs on a power supply through AC.

So, does it work? You bet.

I put two regular ice cubes in a small plastic container and set it on top of the new unit. The ice cubes completely melted in 1 hour and 40 minutes. Then, I took that same container and placed two identical ice cubes in it and set it on my desk. It took 3 hours and 20 minutes to do the same thing. And in case anyone is wondering, the room was at 23 degrees Celsius throughout the experiment.

I think it looks like a NASA Lunar Lander.

Defrosting My Food (Part Two)

So here is the second half of my project to defrost my lunch (or whatever else) utilizing old computer parts.

Warning: Be certain that if you are planning on replicating this project for your own use (which is fine with me), take extra special care when removing the circuit guts from the inside of the power supply unit. There are large capacitors and other assorted things that can quite possibly give you an electric shock, the likes of which you have never experienced. This shock can cause serious harm and quite possibly, death if you are not careful as to what you are doing. I will not be held responsible as this is strictly an experiment of my own and I am a certified computer technician who is well aware of the risks.

The first plan of attack I had was to gut an old computer power supply (PS) and use the box as a sort of plate/ air chamber defroster. I left the fan inside of the unit and attached it to the switch which is also already installed in the power supply. On the top plate, I attached an aluminum heat-sink from a processor and even used the 'transfer paste' between the two surfaces.

When this is assembled again, the fan will pull the air in from the ventilation side of the PS box, pull it across the heat-sink and out of the front of the unit. When you put something frozen on top of the (PS) box, the cold is transferred to the box itself and absorbed by the heat-sink. Pulling room temperature air across the heat-sink will help to warm it up.

I tested this device and found that it worked pretty well as expected.