Raspberry Pi Forums

So i've been thinking, based on the GPIO layout that is used on the pi 2, I can see that there are 2 5v outputs and one ground. Is there a way that I could connect one of those larger 10v DC fans to the raspberry pi instead of this small and noisy 5v fans?.

The goal of this would be to increase airflow, while decreasing the amount of noise that the fan creates. The fan would have to be less noisy than one of those 5v fans, (even if it includes slower a RPM). As long as I get a more quiet fan and increased airflow.

I know this question isn't related to the topic, but is there a way to connect a fan to the GPIO and be able to control the fan speed? Im a noob when it comes to linux, so I would appreciate if you guys explained this stuff a little more.

Its 5v and another pin for 5v. They are there for data that requires two separate lines.
They are not independent; you cannot connect them together to get 10v. And you cannot connect them in parallel to get 4Amps either.
You can connect a 12VDC computer fan to the 5V for low air flow to cool off the pi if you have it working inside an oven.

BTW there are 2x 5V, 2x 3.3V, and 8x ground.

Are you planning to run your Pi in an environment that is too hot for you to withstand? If not, why do you want to attach a fan to it?

Don't do it. You don't need a fan.

Did we say that already.

To get 10 volts you will need a 10v power supply from somewhere.

To get speed control you will need something to pulse width modulate that 10v

Now, those are interesting problems to solve in themselves. But, perhaps you have better things to do with your Pi than figure out how to drive a fan you don't need.

Scott Chiste wrote: connect one of those larger 10v DC fans to the raspberry pi instead of this small and noisy 5v fans?.

I'm not sure what 10V fans are, usually they are rated at 12 volts or 5 volts because those are voltages available with PCs. The 12 volt version will often spin up at 7 volts and be less loud since it is going slower than at 12 volts. I don't know, but I suspect they won't run at 5 volts and you wouldn't want them to stall out.

W. H. Heydt wrote:Are you planning to run your Pi in an environment that is too hot for you to withstand? If not, why do you want to attach a fan to it?

Is 17°C too hot to withstand?

My Pi2B sits inside a vertical case above a 'green' 3.5" hard drive and just reaches 85°C when worked hard with no heatsink or fan with an ambient temperature of only 17°C. That means that it's definitely going to throttle back when I'm gaming in the summer, and that will have an adverse affect on framerates. I know this will be a problem to me as it was a problem with my previous Pi setup.

Admittedly, it is fairly heavily overclocked too, as was the old Pi, but there is no "you don't need no steenkin' fan!" blanket rule. A few of us operating at perfectly normal ambient temperatures most certainly do need heatsinks and/or fans if throttling-avoidance is desirable for performance-related reasons, although I have no problem in accepting that we are a small minority.

Horses for courses.

GTR2Fan wrote:

W. H. Heydt wrote:Are you planning to run your Pi in an environment that is too hot for you to withstand? If not, why do you want to attach a fan to it?

Is 17°C too hot to withstand?

My Pi2B sits inside a vertical case above a 'green' 3.5" hard drive and just reaches 85°C when worked hard with no heatsink or fan with an ambient temperature of only 17°C. That means that it's definitely going to throttle back when I'm gaming in the summer, and that will have an adverse affect on framerates. I know this will be a problem to me as it was a problem with my previous Pi setup.

Admittedly, it is fairly heavily overclocked too, as was the old Pi, but there is no "you don't need no steenkin' fan!" blanket rule. A few of us operating at perfectly normal ambient temperatures most certainly do need heatsinks and/or fans if throttling-avoidance is desirable for performance-related reasons, although I have no problem in accepting that we are a small minority.

Horses for courses.

So...you are heavily overclocking and loading it down, plus putting next to a heat source (the HDD) and you are--just barely reaching the temperature at which the Pi starts to throttle itself. Is your gaming going to hammer the system more than what you are already doing? Possibly cooling the HDD would be more effective than using a fan on the Pi. (And besides, a fan without a heatsink is likely to be less effective than a heatsink without a fan.)

W. H. Heydt wrote:So...you are heavily overclocking and loading it down, plus putting next to a heat source (the HDD) and you are--just barely reaching the temperature at which the Pi starts to throttle itself. Is your gaming going to hammer the system more than what you are already doing?

No, but the ambient temperature is likely to exceed 17°C frequently, so the Pi would be throttling frequently without the aid of supplementary cooling.

Possibly cooling the HDD would be more effective than using a fan on the Pi. (And besides, a fan without a heatsink is likely to be less effective than a heatsink without a fan.)

There is no way to effectively cool the HDD separately without removing it from the case altogether. Besides, it's a 'green' low-power drive with a power consumption of only around 5W, so the heat it produces is significantly less than the Pi produces when the overclocked GPU is being pushed hard.

As stated in my previous post, I have both a fan and a heatsink. The fan is in the back of the case sucking room temperature air in just below the Pi which then exhausts around the USB ports on the back of the Pi near the top of the back panel, so there's a degree of convectional cooling going on at all times even when the fan is stopped. There is a 20-vane 14x14x10mm heatsink on the BCM2386 with the vanes oriented to facilitate easy convectional flow, ie, upwards.

Neither on their own is sufficient to guarantee no throttling if the ambient temperature exceeds 17°C. Using both together gives me roughly another 10 to 12°C of headroom which means that throttling won't start to take place until the ambient temperature is approaching 30°C, which doesn't happen very often in my part of the world. The fan doesn't start until the system reports an SOC temperature of 70°C. It then ramps up from there to full speed at 85°C, so it's not running the vast majority of the time anyway.

I think far too many people vastly underestimate the amount of heat the GPU kicks out when it's overclocked and being pushed hard. The heat generated by all 4 CPU cores of a Pi2B being pushed hard is very small by comparison. You can rest assured that I've not gone to all of this trouble without having a perfectly valid and logical reason for doing it. My technical upbringing and vocational background wouldn't allow me to do that.

I think far too many people vastly underestimate the amount of heat the GPU kicks out when it's overclocked and being pushed hard. The heat generated by all 4 CPU cores of a Pi2B being pushed hard is very small by comparison.

Yes, most of the area of the chip is taken up by the GPU.
You are lucky your Pi gets to 85C at all. During overclock stress testing, all four Pi2's I tried became unstable before the temperature reached 70C. A small heatsink was enough to drop the temperature into the fifties - and I set the temperature limit to 65C to remove the overclock before it gets unstable (though with the heatsink it will never reach that).

I would not use a fan on a Pi, I like the silence, and no moving parts!

It seems to me that the people who keep saying the Pi never ever needs additional cooling have not done any extreme overclocking - or have never properly stress tested their overclocks. The Pi behaves just like any other computer when overclocked - its just that a £1 stick on heatsink is often enough, in contrast to the massive cooling solutions that x86 hardware needs.

jahboater wrote:I would not use a fan on a Pi, I like the silence, and no moving parts!

Me too. Due to the fan being thermally controlled, it never runs when the Pi is performing normal duties, so there's complete silence except when 3D gaming.

It seems to me that the people who keep saying the Pi never ever needs additional cooling have not done any extreme overclocking - or have never properly stress tested their overclocks. The Pi behaves just like any other computer when overclocked - its just that a £1 stick on heatsink is often enough, in contrast to the massive cooling solutions that x86 hardware needs.

Agreed. Stress testing one part of the system in isolation (ie, the CPU(s) or the GPU or the RAM rather than all together) seems to be a common mistake made and is no proof of stability as it doesn't generate the temperatures involved or the inter-device transactions involved in a full-on stress test. Most people claiming complete stability at crazy clock speeds have never actually stress tested at all yet still claim complete stability on the basis that they can browse the web or run a media centre program without crashes.

I fear that the art of overclocking in general has already been too heavily polluted by false claims for a general web search to bring up many genuinely meaningful results for most hardware by people who simply don't know how to overclock. There's far more to it than just chucking a few numbers into a PC BIOS or a Pi config.txt file and making unscientific assumptions. Luckily a few of us still stick together and beat the drum on appropriate methods of stress testing an overclock, but I'm afraid that we are slowly becoming a dying breed.

Hi Scott,

Scott Chiste wrote:So i've been thinking, based on the GPIO layout that is used on the pi 2, I can see that there are 2 5v outputs and one ground. Is there a way that I could connect one of those larger 10v DC fans to the raspberry pi instead of this small and noisy 5v fans?.

Voltage is a electric potential difference between two points, combining voltages sources result on subtraction* (see kirchhoff's laws).
5V - 5V = 0 (common ground, potential between voltages.)
To get 10V, need to add both voltages. To do one of voltages need to be negative.
5V - (-5V) = 5V + 5V = 10V (common ground, potential between voltages.)
But, RPi not have a -5V rail.

* In fact it is a sum of voltages, but voltage sources are bipolar (have positive and negative poles).
Lets try battery association.
This [} is a my battery symbol, [ is the negative (-) pole and } the positive pole (+), a hypothetical 5V battery.
[}+[}=10V -
[}+{]=0V
{]+[}=0V
[}+[}+{]=5V

Voltage pins on RPi GPIO header (or other places) have this equivalent battery association {]+[}, the junction ]+[ is called common or ground. Also 3v3 have same common.
this explanation may be have some inaccuracy.

Is possible to get 10V or more from 5V using a DC to DC converter. A boost converter type or step up.

But, to power fan, use a primary power supply.

I know this question isn't related to the topic, but is there a way to connect a fan to the GPIO and be able to control the fan speed? Im a noob when it comes to linux, so I would appreciate if you guys explained this stuff a little more.

To control fan speed need to use PWM. RPi have only one hardware PWM channel available on GPIO header. But, can be use a software pwm on other pins. This pin need to be connected to driver circuity.

Get one of these, https://www.sparkfun.com/products/11296 and you can power your Pi, the hard-disk and the fan from the same power supply.

(Countless others exist; it's a very common requirement.)