Hello fellow tinkerers, the fan I made here was for a specific purpose (my home theater receiver creates a lot of heat that gets trapped in the cabinet that it's in, so I decided to build a fan system to vent the heat out the back), but this type of fan can be used for many applications. Since I had the metal grille, switch, and case fan laying around my house, I only spent one dollar on the power adapter at Goodwill.
What you will need:
-Drill and drillbits
-Dremel tool with cuttoff disk
-12 volt DC adapter
-Computer case fan
Step 1: Prep the Fan and Power Adapter
I got my fan out of an old, useless desktop computer, but I'm assuming most people would simply buy a new fan (an 80mm fan like what I used should cost no more than 5 bucks). The fan probably has a plug end to it, so you're going to want to cut that off, leaving as much wire attached to the fan as possible. Strip the wire ends 1/4 of an inch.
Now take your 12 volt adapter and do the same thing, cutting off the small end. You want the plug and as much wire as you can possibly get. Just like the fan wires, strip the ends approximately 1/4 of an inch.
Step 2: Making the Connections
Okay, now that you have your wires cut and stripped, you need to connect them to make the circuit. Connect the negative wire on the fan to the negative wire on the power adapter by twisting them together and securing the connection with a little bit of solder, followed by a coating of electrical tape.
Now you need to connect your switch to the positive wires on the power adapter and on the fan. Depending on what kind of switch you have, there are either going to be two leads or three leads. If there are two, then it doesn't much matter which lead goes to which wire.
***If your switch only two leads, you dont need to worry about this next paragraph**
If there are three (like on my switch), you will need to determine which leads are going to work for you. Generally, the middle lead is a common lead (in other words, it doesn't matter which wire is connected to it), but the two on the ends are what you need to test. Simply keep one wire connected to the common lead, and test the two other leads by connecting the other wire to it and turning the switch on and off (while your adapter is plugged into an electrical source). Whichever lead allows you to turn on the fan is the one you want. Now all you need to do is solder your two wires to their correct leads, and wrap the connections in electrical tape. I also wrapped the unused lead on my switch to prevent any accidental shortages.
The reason why there would be three leads on a switch is because that particular switch is for AC current (ex. a standard wall mounted lightswitch). The switch I used is normally for AC current and is also normally illuminated when it is turned on, but AC switches will also work for DC circuits like what we have here, you just won't need one of the leads on the switch, and the switch won't light up when it is in the on position.
Step 3: Add the Metal Grille
In order to mount this fan where you need it (in my case, a cabinet), you will need some sort of bracket or mounting tab to secure it. I decided to make my mounting tabs out of a small sheet of metal grille that I scrapped off of an old outdoor speaker. The goal is to provide a sturdy mounting bracket and also to provide sufficient air flow for the fan. I used tin snips to cut the sheet to size, followed by some filing to get rid of the sharp edges on the metal.
I measured and cut holes for the screws that go to the fan, and I used my Dremel tool to cut a rectangular hole for my switch to fit through. To put the switch in backwards without having to redo the solder connections, I just used pliers to bend the metal around the edge of the hole, then slipped the switch right in and bent the metal back in place.
Congratulations! You now have a 12volt cooling fan that you can mount... well, anywhere really. Remember that if you are trying to cool off a container of some sort, or a cabinet, orient the fan so that it is pulling the warm air out. If you accidentally mount the fan backwards, all you need to do is unscrew it and re-orient it.
Thanks guys! If you liked the 'ible, rate it 5 stars and subscribe to me, I will be posting many more projects in the future. Happy tinkering!