PC fan on 30 volts - RC-Monster Forums

BrianG · 09:53 PM

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 · 07.28.2006, 10:03 PM

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 · 10:28 PM

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 · 07.28.2006, 10:35 PM

Thanks Brian,i get it now.

glassdoctor · 07.29.2006, 12:04 AM

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 · 07.29.2006, 12:11 AM

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 · 01:01 AM

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.