# COMMUNITY : FORUMS : TECH

## Laptop Fan Help!

so i bought a 2.8ghz laptop from a guy for \$30

i fixed EVERYTHING, invested about \$200 of my hard-earned money
and now the CPU fan wants to crap out on me >: (
the fan works, the circuitry that controls the fan has failed (on the mobo)

so what i am asking is that you help me!

i need to be able to regulate the 12v that comes from the battery into lower voltage, with a variable power supply,
https://www.instructables.com/id/How-to-Build-a-Bench-Top-Power-Supply/

I need someone to do the calculation so that i can regulate voltage form 4.5v - 12v

what would be the resistance values?
VOUT = 1.25 * ( 1 + ( R2/R1 ) )

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110100101108 years ago
you sure dont want to do this with resistors. they turn power to heat so you waste the battery for nothing and get more heat to take out of the computer i'd do a circuit that keeps the fan off and turns it on in full speed only when temperature rises. when temp falls down it shuts down. such circuit exists in all modern laptops you need for that a thermistor + N555 timer chip + some extra electronics + good high flow 5 V fan some fans from video cards may fit in laptop cooling devices. most of them are 5 V. they are not too reliable though you can take 5 V from the hard drive power supply. its on one of the pins near the center on the IDE connector. look online to find the exact pin. DO NOT do that if the computer can turn off the drive thru power management - you can overheat the computer without fan. its better to find 5 V elsewhere on the board (test the large planes in the power area of the board)
AnarchistAsian8 years ago
idk, computers aren't really my thing...
NachoMahma8 years ago
. You could install a 5 or 12V fan on the CPU and run it straight off the PSU.
.
. I have an Apevia Model FC-01 fan speed controller (12V in, 5-11.7V@1.2A out) that I can donate if you send me a postage-paid box.
Sandisk1duo (author)  NachoMahma8 years ago
as you can see, i have a laptop, i kind of want it portable...
8 years ago
. For item 1, use the laptop 5/12V to a HDD. . For item 2, it's pretty small; well within your two matchboxes.
Sandisk1duo (author)  NachoMahma8 years ago
5/12v to HDD <- what? #2, i need the circuitry to be small, not the fan, the fan works, the electronics that control the speed of rotation/voltage
8 years ago
. 5V or 12V power to the laptop's Hard Disk Drive. You may have a spare connector inside the laptop. . Follow the link. It is a small controller mounted on an expansion slot cover plate. Two screws and the plate comes off. The connectors are the standard 4-pin Molex, but you should be able to splice it in where you need it.
Sandisk1duo (author)  NachoMahma8 years ago
i can build that thing myself what i need is a circuit that can boost 5v usb to 12v
8 years ago
. Googling 5V to 12V turns up some good stuff, including this. Append " +schematic" and it should get rid of a lot of the chaff.
.
. Why are you so adamant about using 5V-to-12V? You should have 12V available somewhere in the laptop. Or use a 5V fan.
Sandisk1duo (author)  NachoMahma8 years ago
well, the fan runs on 12v,
i can't replace the fan because it is unigue, and a replacement is around \$40

i can run the laptop fan off the 5v usb, the temperature reaching 60+ celcius

so i want to be able to run the fan at full blast, when needed

i checked the voltage of the battery and it is 12.5v, so the problem with powering the fan is solved

the next task is to regulate the 12.5v into lower voltage, and be able to change it from 4.5 - 12v i know the LM317T is the voltage regulator for me

i need the resistor values for it;
https://www.instructables.com/id/How-to-Build-a-Bench-Top-Power-Supply/

put that thing inside the laptop, with the potentiometer sticking out

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