BleepingComputer.com: Some advice needed about fan voltages / amps / wiring etc..

Hey all,

I've tried all kinds of laptop cooling pads (all of which ran off USB), and they are all too weak to offer any sort of decent cooling (and thus the laptop goes into 'limp' mode if it overheats). Right now, I have to place a huge desktop fan at the side of it, to stop it going into limp.

I bought a "NotePal U3", which has removable fans, and intend on replacing them with decent spec fans. This was all going great, until I realises I remembered sweet nothing about electronics from my childhood days, and got confused by terms such as "rated voltage" and "operating voltage range".

Sooo, to cut a long story short, I don't want an easy "this is how to do it" answer (as this take away the fun lol), but a poke in the right direction would be really helpful, as I really don't know wtf I'm doing lol.

A ) If I had fans which were capable of up to 4000RPM, how would I regulate the power going into it, so I could control the speed? (I assumed it'd be like a dimmer switch, but on a smaller scale??). The cooler came with one, but it's only like 500mA going through it.. if I was to use it on a higher power circuit, would this cause problems?

B ) Based on the following specs of the fans (and there will be 3 of these on the same circuit), what voltage/wattage would the power adapter need to be?
- rated voltage (VDC) - 24
- operating voltage range (V) (20.4 ~ 27.6)
- rated current (A) (0.24)
- rated input power (W) (5.76)

C ) I'd really like to avoid the scenario of waking up and:
*) finding my computer room on fire.. in fact no, finding my *anything* on fire.
*) blowing fuses on the switchboard
*) anything else that would cause my girl to ban me from ever touching anything electronic ever again lol.

- any hints and tips you can give me to safe guard against stuff like this happens, would be really great!

Thanks for taking the time to read, would really appreciate any comments

Cal

If the laptop is overheating, I would make sure the heatsink is clean and the fan works. After that, try reapplying thermal paste on all components attached to the heatsink.

If you still need the powerful fan to keep it cool, look for a 24VDC power adapter with 1A or higher rated current. Those fans will not even spin on 5V from a USB port. To control the speed, you can make or buy a fan controller that will change the fan's speed based on temperature or a manual control.

lti, on 26 April 2011 - 05:28 PM, said:

Hey man, thanks for the reply!

If the fans combined don't go above 1amp, and are all at 24V VDC, will it be dangerous / damaging to use an adapter which is rated => 1amp and at 24V?

Cheers

Cal

Shameless self bamp.

There shouldn't be any damage. The fans draw 0.72A combined, and using an adapter that can supply more current will simply mean that less stress is placed on the adapter.
Controlling the speed of the fans is more difficult. Do you want to be able to control the speed manually, or do you want the fan speed to change automatically when the laptop heats up? The second of these will require the ability to solder on a circuit board.

lti, on 01 May 2011 - 01:16 PM, said:

Hey again! Just the ability to control the speed myself would be sufficient.. It doesn't even need to be a 'rotating switch', it can just be a flip switch which sends it to half speed. Could you possibly recommend any pages which show similar diagrams to what I am looking to achieve? Doesn't need to be exact, just something where I can see the general "flow" that you'd need to take.

Cheers

Cal

To lower the fan's speed, you can place a resistor in series with the fan. The resistor will need to be rated for high wattage, probably around 25W, and have low enough resistance to allow the fan to start without switching it to full voltage. A switch can be used to switch between low and high speed. Unfortunately, I have no diagrams showing this.
You can also use a rheostat, such as this. That one is designed for 12V fans inside a desktop computer, but you can see how it is wired and the resistance and power ratings that are required for either type of control. The resistance required depends on the fans you are using.

lti, on 01 May 2011 - 03:20 PM, said:

Nice, thanks for this! Last question, would it be a good idea to simulate this first, with something like LogicWorks 5 (http://www.capilano.com/lww_5) ??

If you can find software that can simulate what would happen if you put a resistor in series with a fan motor (usually a DC brushless motor), you can try simulating it. Make sure that the voltage across the fans with the resistor in series is above the fans' starting voltages (the minimum voltage required to get the fan to spin). If this is not given by the fan manufacturer, you will have to try connecting various voltages to the fans and seeing if they will start on their own at that voltage.

This post has been edited by lti: 01 May 2011 - 03:53 PM

lti, on 01 May 2011 - 03:53 PM, said:

Alright, I'll let you know how I get on. Thanks for putting up with the noobish questions, it's really appreciated!

Cal

I just remembered this: Did you make sure the heatsink is clean and the laptop's fan works? It sounds strange to have a laptop overheat if its cooling system is functioning properly. You will have to disassemble the laptop to clean the heatsink.
What brand and model of laptop is this?

Let's back up here for a moment.

What is the temperature showing in the BIOS?

You can download SIW to read the temperatures. These may not be the exact figures shown in the BIOS, but will be close enough to see what is going on. When you go to install SIW pay attention once you start, there is a Crawler which already has a check mark to enable its installation. Unless you want this feature remove the check mark.

What do you mean by "it goes into limp mode"?

Have you tried using canned air to blow out the vents?

Is the computer sitting on a solid surface?

Unless this is an older computer the chances that the thermal compound has dried out would be high.

A couple of things to clarify..

The laptop is known to suffer with high temps (and has done since day 1). It is only encountered however, by running full screen games (such as bf2142, mw2 etc). The spec of the laptop does bring it within the gaming category, and the manufacturer recommends it for gaming too.

Also, I have not been doing any overclocking of any sort (rivatuner was used to monitor temps, that's all)

lti, on 01 May 2011 - 05:19 PM, said:

Acer 8943G - 9 months old, bought brand new.

dc3, on 01 May 2011 - 11:03 PM, said:

Thanks for the link, nice lil program that!

Here's a screenshot taken out of gaming.



(this is in the event of gaming)
Without the desktop fan, it'll peak to around 90-100c, then fall back into "limp mode / low power mode" to cool off to around 70c, then go around in circles.
With the desktop fan, it'll stay steady at around 70-75c.
I measured this with the temperature monitor within RivaTuner.

dc3, on 01 May 2011 - 11:03 PM, said:

In regards to "limp mode", after playing for a little while, the FPS will drop to around half it's original whilst the laptop tries to cool itself down. By placing a desktop fan behind it, the FPS stays stable at its full rate (90fps) all the time.

dc3, on 01 May 2011 - 11:03 PM, said:

Nope, I never leave the laptop on a solid surface, it is always either on the cooling pad, or propped up at the back with a book edge.

dc3, on 01 May 2011 - 11:03 PM, said:

Not yet.. Because the laptop suffered with this problem since day 1 (brand new sealed), I'm not sure this would resolve the situation (although it wouldn't hurt to give it a blow every few months, I'm sure!)

What is the make and model of this laptop?

Not knowing what flavor your computer is I can only suggest that there are laptops that are advertised as being able to play games, but with what amount of success is the question. My concern is the possibility of damaging your CPU by overheating it.

By going "limp" you mean that the frames per second drop? Is that all that happens, it doesn't shut down?

Some people will use their laptop with it sitting on their lap, I was just trying to find out if this was the case by asking about having it on a solid surface.

dc3, on 02 May 2011 - 09:57 AM, said:

It is an Acer 8943G.

http://www.pcpro.co.uk/reviews/laptops/359500/acer-aspire-ethos-8943g
http://www.trustedreviews.com/Acer-Aspire-Ethos-8943G_Laptop_review
http://www.slashgear.com/acer-aspire-ethos-8943g-5943g-hd-notebooks-debut-2479012/

dc3, on 02 May 2011 - 09:57 AM, said:

Like with anything, the more intensely you use something, the quicker it is going to expire. I know that even though the manufacturer recommends it for gaming, I am most likely reducing the lifespan of the laptop, but this isn't of much concern (as long as it survives past the warranty, I don't mind)

dc3, on 02 May 2011 - 09:57 AM, said:

Yeah. the graphics card enters into "low power mode" (sorry, I thought it was called limp mode), and then waits until it's hit 70c, then goes back into high power mode again. So far, the laptop has never powered down due to overheating, but this is mostly likely because you physically can't push it past a certain point.

dc3, on 02 May 2011 - 09:57 AM, said:

Nah, I don't ever really sit with it on my laptop, because I'll end up infertile with the kinda heat this thing generates lol.

Another side note.. in case you're wondering why I do gaming on a laptop.. I am constantly moving around the country (due to work) on a daily basis, and it's very rare I get any time to sit at my own desk, and trawling around a huge case + monitor wasn't really an option. So, the laptop, although not the best performance, does the job very nicely! (minus the heat lol)

This post has been edited by sleepycal: 02 May 2011 - 10:04 AM