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Step 5Let 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!
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!
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Rated Voltage: 12 volts
Operation Voltage: 10.2-13.8 Volts
Input Current: 0.15 Amps
Input Power: 1.8 Watts Max
but im not to sure what the Ohms ratings are on the fans. now ive found a few different power supplies lying around my house to choose from. here are thier specs.
Output: 12V- 1.66A
Output: 18V- 600mA
Output: 12V-1000mA
if anyone could help me out, that would be great :)
Couldn't you power the fans through a USB port on the laptop?
Or would they draw to much power through the laptop power supply or battery?