PC fan on 30 volts

[Gustav]

I'm wondering if it might be possible to run one of the very slow 80mm fans on much higher voltage,some of the ultra quiet ones only spin 1800rpm on 12v.

Is this a very bad idea? I don't mind the fan dying,they're cheap,concern would be if it could short out and kill other stuff.i want a fan i can run straight off the main batteries from 4s to 8s.Are there some very small voltage regulators i could use instead.?

[GeeReg]

You could wire in some resistors or a potentiometer to adjust it if you want. 30v would kill it pretty quickly I think.

[coolhandcountry]

If you chat with metal man. He could probably tell you how to make a bec 12 volt version. That would be the thing you need. He made a 6v model.

[MetalMan]

Or you could use a linear regulator to drop the voltage. I think a single 12v regulator (7812, can be gotten at many electronics stores) should work since it should only have about 2watts to dissipate as heat.

[Gustav]

Thanks,there's a 78S12 aswell that's 2A output.

I'm confused though about how i would wire it up,they have 3 pins,wouldn't i need something with a -ve and +ve in and a -ve and +ve out?(like the UBEC) if so,how is that done? Is it obvious i know sod all about electronics?:005:

This guy runs his fans on 24vhttp://www.afrotechmods.com/fanmod.htm and i'm talking about a slow fan here,i would try it,only concern would be if there's any chance it could short out my batteries when it dies.

Was thinking about running a battery just for the fan,a camcorder battery or something,and having that and the fan just attach to the body.That'd keep the birds nest down a bit.Also thought about a 3s or 4s reciever pack,with the fan and UBEC coming off that.

I suppose the alternative would be to have planty of extra heat sink,some properly effective air ducts in the body and just never slow down.

[BrianG]

Looking at the chip so the lettering is facing you, from left to right, the three terminals are input, ground, output. Even though the IC can supply 2A, it will only need to supply what the fan draws. Small fans usually pull no more than 0.25A, especially the slow ones. It is a 12v fan? What voltage do you want to run it at? I wouldn't go higher than 20% higher than its rated voltage or it may shorten its life. You can figure out how much power the regulator will dissipate by the formula:

regulator_dissipation = (supply_voltage - fan_voltage) * fan_current.

When the fan dies, it will most likely open circuit. And even if it does short out, the relatively tiny wires to the fan will act as a fuse and burn up, or the regulator itself will burn up.

[Gustav]

Yeah 12v fans,i normally run 4s or 7s lipo and at first i was thinking about running it straight from the main batteries with no regulator.how would i wire up the regulator? i'm still confused about that.

Are there any 5v fans that can shift a decent amount of air?

[BrianG]

Wiring it is really simple - especially if you stick to 12v (you can wire a 12v regulator to provide more voltage).

- Run a small 20GA wire from + of your main battery to pin 1 (left) of the regulator.
- Run a small 20GA wire from pin 3 of the regulator to the + lead of your fan.
- Run a small 20GA wire from - of your main battery to pin 2 (center) of the regulator.
- Run a small 20GA wire from from pin 2 (center) of the regulator to the - lead of your fan.

Put a heatsink on the IC and use a thermal insulator pad. IIRC, the tab on the IC is common to the output pin and if it touches any negative lead, it will damage the IC.

I'd stick to the 12v fans as they will move more air and are far easier to find. You can use a fan from a computer video card, chipset fan, CPU, etc and those all use 12v.

[Gustav]

Thanks Brian,i get it now.

[glassdoctor]

Just a thought here... if you want to run two fans, you could just hook them up in series and they would each see 15V which would be perfect for a little voltage boost.

I have seen some pc cooling stuff that piggybacked two fans together... and I have thought of doing that just to get more airflow on my 12V fans.

[BrianG]

That is another solution as long as the voltage is 24v-30v. However if he wants something that will work with batteries below 24v (4s and 5s), then the regulator might be his best bet.

[Gustav]

I'm been toying with the idea of using the venturi effect and doing away with fans altogether,i'm trying to figure out what ratio between input and output area of the tube i would need to tripple the air speed.If i could get a 60mph wind blowing over the thing every time it goes 20mph then i don't think there'd be much need for a fan.

Might have to be more like double the air velocity so the OUT isn't too small or the IN too big to be practical.dunno haven't figured it out yet,there's online calculators for it though.

Drag might be a problem though,as might ripping the body clean off at 50mph:005:

The problem with just cutting holes in the body is it opens out after it enters and the air slows down so we're not really getting all that much cooling at these relatively slow speeds,i think maybe what we need is a tube or tubes going to the areas we want cooling.

Originally Posted by Gustav

The problem with just cutting holes in the body is it opens out after it enters and the air slows down so we're not really getting all that much cooling at these relatively slow speeds,i think maybe what we need is a tube or tubes going to the areas we want cooling.

Gustav, I recon a couple of ice cream cones through the windscreen could do the job.....they would have to be double scoop size obviously.....
That just leaves you to work out how much to bite off the end.......:004:

Ive always run my fans on 16-18 cells ( knowing sod all too :027: ) The one thing I am sure of now, is the neon ones seem to last consideably longer than the standard fans.......I plainly have no idea why this would be, just though id pass it on.

[Gustav]

Originally Posted by cabking

Gustav, I recon a couple of ice cream cones through the windscreen could do the job.....they would have to be double scoop size obviously.....
That just leaves you to work out how much to bite off the end.......:004

That sounds a bit technical,so far all i've got is a fairy liquid bottle jammed in the grill with a plastic pipe stuck to it,it's sure to catch on.

[BrianG]

Lol, sounds too complicated. Why not have a small tank of liquid Nitrogen? Or use a Peltier cooler?