Introduction: DIY Laptop Cooler

By
About: Jack of all trades, master of none, Sigh...... how does one get good at something when there are so many things in this world to learn?

A plexiglass constructed notebook cooler equiped with spiffy lighted fans for some trippy late night surfing/gaming safari's..

Step 1: Getting Some Stuff Together...

You will need some stuff, so dig around in your parts drawer for the following items:
-a switch (toggle, SPST type)
-some wire (about 22g, roughly a foot or two, coated!)
-sheet of plexiglass or acrylic (a like the 1/4" stuff)
-2 comp. fans (standard 80mm or 120mm)
-some nuts and bolts (#8-32 x 1 1/4")
-old power supply (for this project I used an 24VDC from an old epson receipt printer)
-some tools (Dremel (of course!), hobby knife, Drill, solder gun, solder (the good electronic component stuff) heat shrink tubing, heat gun or blow torch)

Step 2: Layout: Customizing Your Cooler

The measurements in the picture are the dimensions for my notebook so be sure to measure yours and adjust accordingly.
First off we start by measuring our laptop to get the dimentions, mine is about 12"x14" so that is what I went with, obviously yours will differ. The initial design calls for a 12"x14" base with 1" piece folded under, a 3" riser section, and another 1" folded under section for the back. This is constructed out of a single piece of Plexiglass that is melted into shape with either a Heat Gun or Blow Torch. I cut the Plexiglass down to 12x18 as per the measurement we just took, 12" for the base + 3" riser + 1" for the front underfold + 1" for the back underfold = 18"?? Well, close enough, it saves me from making 2 cuts and that means one less opportunity to break the plexiglass. (I've cracked a lot in the past.) (Note: leave the protecting sheets on the plexi until the heating gun part to keep from scratching it up).
Score your plexi with a utility knife and straight edge, line up the scored edge face up with the edge of a counter or such and press down to snap the edge clean.
Next lay the plexi over the back of the notebook for fan placement. My Alienware has two intake areas on the bottom and the exhaust ports on the sides. Mark the corners of the fans so we can scribe the circles and cut them out.

Step 3: Fabrication: Making Stuff, Breaking Stuff

Next using a straightedge, draw a line from the opposite corners of each corner of the marks you made from the fan placement. You should make an X, the center of this X is the center of your circle. Using a compass or Scribe set to 1.5" (or 40mm for those metricly inclined) draw a circle using the center of the X as the center point, giving you a 3" or 80mm circle. Repeat for the other fan.
Using a dremel with a circle cutter set for 1.5" radius, cut out the cirlcle. It might help to use a automatic center punch to mark the pivot point to have a deeper hole to move around on.
Once this is complete you can use some 400 grit sand paper or a fine toothed file to clean up and square the edges if need.
The Switch hole is cut with a cut-off wheel and the power cord hole is drilled. Test fit the switch and the cord keeper, since it is much more difficult to make any modifications after we make the bends.

Step 4: Fire Baby, Fire!

Here is the fun part, shaping the unit. I suppose a heat gun would have been more practical, not to mention safer, but I used what I had available and an acetelene torch is all I had. The first fold we will make will be the base of the riser section (1" mark), so lay the line we marked on an edge of something straight ,(better if its fire proof and not an old dry 2x4 like I used). I'll pretend you are using a heat gun since that would give you more control over the process without cooking the plexi like i did. Moving the Heat gun back and forth along the line, slowly heat the area until the overhanging plexi starts to sag. After another couple of passes, press the edge down using the fire proof edge you are heating on as a crease. This will be the 90 degree bend as shown in the illustration.
Next will be the 60 degree bend, it isn't approximate so just start heating and bending until you get the angle you want. I used another piece of wood flatten the crease by applying a bit of pressure until the plexi cooled enough to retain the shape I created.
For the final fold, I heated up the plexi, folded it under and left it to cool in the desired angle that allowed the unit to sit square on the table. If it wobbles while sitting flat you can use the heat gun to adjust the fold angles until it is right or just works for you. Also make sure you are folding the correct side, you want your fans to be exactly where you want them, not on the opposite side!

Step 5: Let There Be Light: Powerslave

The fans get installed with the nuts and bolts, make sure you have the fans facing in the correct direction according to the design of your laptop. If your laptop has fans blowing out the exhaust from the bottom then you want your fans to face down to futher aid in the expelling of hot air away from the unit, increasing circulation. Mine has intake fans on the bottom and exhaust ports on the side so I chose to face them up to send more air volume into the laptop. Next add the switch to it proper place and we'll start preping the powersupply.
Using an old wall wort power supply is an easy way to get this thing running but first you have to make sure that you either have enough power to run the fans or if there is too much that it will cook them and perhaps start a fire and burn up your laptop. In order to avoid both these situations we need the help of our friend Mr. Georg Ohms. He came up with neato Law that defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. . There are many Ohms Law calculators on the Web that will do the math for you, all you need is two of the four values and it will compute the rest. Now, I am not a electrician, nor do I have any certificates or training, so alway talk with someone who is qualified when attempting such electrical tom-foolery. Strip the output connector plug of the powersupply carefully with a ulitity knife so you can see which is the + and - . Printed on the transformer it should tell you which led is + and - , so once you strip back the plug housing you can see which led is what. Once you have determined which is pos. & neg. , mark them with tape or something so you don't get them mixed up.
I found a 24 Volt 2 amp power supply from an Epson reciept printer that was just about brand new! Now the problem gets interesting, how do we get 24 volts down to a usable 12 Volts so our little fans don't try to take off when we flip the switch. Lets see, how about we wire them in Series? You know, wiring the positive of the first fan to the positive of the powersupply, the negitive of the first fan to the positive of the second fan and then the negitive of the second fan to the powersupply ground led (see the diagram). This will double the Ohms (60 X 2) to make 120 Ohms since adding them in Series creates more resistance (add the value of the Ohms per fan to get the total). So in your Ohms calculator add the 120 Ohms on to the 24 Volt power supply, hit calculate and it gives us .2 Amps at 4.8 Watts. The .2 Amps is what our fans desire and the fact that we wired them in Series will make each take 12 Volts away from the 24V power supply, so 24 Volts divided by 2 (2 fans) = 12 Volts. So each fan get its required 12 Volts and the proper .2 amps, and all is well. If the power supply was only 12V and we wired the fans in series then each fan would only be running on 6 Volts each or 1/2 the speed they can run. So less voltage and the fans would spin slower which would be OK as long as the Amps were within the fans range and you didn't mind less cooling potential. More voltage will make them spin faster and either burn out or burn up.
The diagram below has the simplified wiring, nothing really complicated once you get the current worked out. You can see that the DC Voltage running through the open circut is 11.87 Volts (we'll call it 12V). I thought about putting a rheostat (speed control) in line to adjust the fan speed in case I wanted quiter operation, but the fans are super quiet so I didn't see any point. After everything is tested and working correctly, break out the soldering iron and the shrink tubing.
The Yellow led coming out of the fans is for monitoring the fan speed when attached to the motherboard. It is not used in this project. I just twisted it around either the positive (red) or negitive (black) leds and stuffed it into the shrink tubing to keep it out of the way. The power cord is feed into the hole we drilled and is held in by the Strain Relief Bushing.Slide the shrink tube on to one end of the wire, twist the two leds together, solder, slide the shrink tubing over the soldered joint and heat with a lighter or heat gun. For the switch connectors I used I used female crimp-on quck connect type lugs that just slide onto the male lugs on the switch. Small cable ties can be used to clean up all the loose wires and secure them from getting caught in the fans.
This project can be found in more detail and a ton of pics on my website. http://www.robertreznik.com/DIY/Laptop%20CoolerV01.htm
Thanks and good luck!