Fan Speed Control Circuit (28K)

po0k

This is a design for a possible fan speed control.
It has not yet been built, tested or thought though clearly, yet.

It works on the simple principle of a voltage divider.
I think this is better then using either a retail Baybus thing or using POTS cos afaik this won't generate as much <?> heat and won't burn out. Plus, it costs damn all.



Key:
Vin= Voltage in, here it's 12Volts DC.
Vout=output voltage, for my intended config it'll be 6V (A), 9V (B) or 12V (C)
Rxx=standard resistor, value of which will directly control the output voltage.

The purple fan speed line is provided merely as an afterthought for the 3-pin molex fans, in which the 3rd pin is used to read the fan speed. Pass though wire.

3-way switch: I want to get one in the form of a knob, as it would look cool.
Any sort of 3 way switch would do perfectly. If it has both +ve and -ve connectors I'll only need to use one, as only the +ve line is switched.
In this config all 3 outputs can be joined to one connector, simplyfying construction.
I managed to scavange a few jumper pin thingies from an old board. I intend to use em.

Formula: Vout= (R2/{R1+R2})Vin
to get a 9V output from a 12V source you'd have R1=330Ohm, R2=1KOhm, so it would be (1KOhm/1.33KOhm)12V=9V output.
when R1=R2, Vout=(0.5)Vin.

I'm going t mount this in a 3.5" bay on the front of my old PC, which has two 12V 80mm fans which are quite noisey. It's also in my room and I'd like to be able to leave it on 24/7.
The CPu is a P200 o/ced to 225 which has a standard Pentium fan on it, which is also quite quiet. I'll try it with the two other fans, mightbuild two of the circuits and have one controlling each fan. Might work in some LEDS too, telling which voltage level each one is at. Have to see about it. It's a lot of area for a 3.5" cover, but I reckon it's possible.

Parts you'll need for each circuit:
3x1KOhm resistors
1x 330Ohm resistor
1x 3-way switch
connecting wire
resin-core solder + soldering iron
Something to mount all the stuff on, standard PCB stuff should do, ask peats.
jumper thingies, maybe some molex connectors
LEDS if you want.
Time.

I'm not going to bother with voltage regulators at the moment, might need one or two for the LEDS if i put em in though.

I have a
a) will therebe any loading problems having more then one fan attached to each circuit?ie too much/not enough current
b) will this generate less/more heat then a POT?
c) Anyone have any extra comments/suggestions?

Hope this works, tis part3 of my modding project, though part 2 (spraying) still has to be started This is what I'll be spending my christmas at.

Gerry

Standard resistors can only handle 1/4 watt each, whereas your fans will be 2 watts or more. I also think your circuit is over complicated, but its too early in the morning to figure it out.

po0k

I was down at the electronics lab in the colelge. ot parts.
They're bigger looking resistors. Your man said they'd do the job. now all that remains is for me to get my ass a multi-meter and a proper soldering iron.....

vac

You could just get a varible resistor, that would do it and look nice too :P

po0k

I know, but I don't want to use them because
a)I don't have enough space for one, this is going in the cubby hole space above a hard drive, the switch being squeezed in the 1/2 inch of space between the drive's front and the blanking panel. Therefore a POT is too big.
b)POTS produce a fair bit of heat for the ones that would be needed for fans
c)POTs burn out, and are expensivee. They're also har dot get at a high enough wattage for hooking up several biggish fans (what i intend to do when i get my big fuk-off tower case).

This is fitting in a midi/mini AT case.

I have a few pi of the innards, just gotta find me a scanner....

The switch i got is only a 2way toggle switch ie: 1 input (12V), choose between 2 outputs (in this case 9V and 12V/6V)
I'm getting a multimeter tomorrow and hopefully a solderin iron.
I'll test it on a bread board if I can before actaully assembly.
It shopuld work, and if it doesn't It'll have cost me nothing, cept the soldering iron and multimeter, both which I'd use anyways...

Gerry

But you are already using resistors! They are going to produce just as much heat as a variable resistor. They get rid of the extra power by dissipating it as heat.

http://www.peats.ie/cgi-bin/shop/db.cgi?view=1&id=3277&type=6&path=13x172x475

Thats the type of resistor I have on my machine. It is not a POT, it is made completely differently, and so can handle more wattage, 5 watts in this case. It won't burn out, I've had mine for over a year. I have a 100 ohm wirewound, and some 20's. The 20's aren't really strong enough, they only bring it down to 7 volts.

I have one controlling 2 60mm ystech fans, they are rated at 2.2 watts each. Another controls the 120 mm fan. They will still fit in your front panel, they won't take up any more depth than a switch.

po0k

Cool, might just have a look at them so after all.

Was think about the LEDS though, might work it around another way.

I'll see.
Thanks, thought POTs were bigger, due to the pix I saw of the various yank Baybuses.

Need to pick up a few fans anyways so i'll be up in peats sometime soon.

Twill take a bit more organisation and consideration for a large combination of fans for my intended tower case, but it'll be worth it.

[EDIT] the 't' in thought[/EDIT]

leeroybrown

SyxPak,

I'm sure you could *cough* borrow a lot of the bits and pieces from the department.

There is also a rather nice tool kit the department are ordering for people at the moment. It has a multimeter, electric soldering iron, screwdrivers, and various other tools. Plus a piece of breadboard. Might be just the kind of thing that tweaking enthusiast such as yourself would find very handy.

po0k

The one for £35??

Might get one so.
The meter is £16 to get on it's own.
A bread board would be handy alright.

leeroybrown

They're £40 afaik.

I've seen one and they seem to be pretty gook stuff. And you do get a fair few screwdrivers and other useful tools. Well worth the £40 anyway, especially for someone like you who will use them a lot.

You'd find it really handy for working on your projects at home in later years too.

po0k

I'll try and get it by next week so....£40 is hard to come by when you're broke, adn even mopre so around christmas/New Year's when you're trying to get pished.

marauder

Try this...
http://www.tweak3d.net/articles/quietcase/2.shtml

po0k

resurrecting this thread.....

Marauder, that's not a bad tweak, but it's very messy for several fans (not saying the diagram above is anything clean )

I can across this in BiT (they've done up the site)

http://www.bit-tech.net/article/

Looking at the PWM one in particular....

logic1

I use a pcmods rheobus controller and it'll always be l33t3r than anything you make

Nah seriously I did have one made from pots but got pissed off with the low wattage capacity. PCmods rheobus has up to 17 watts on each pot afaik.

Plus I'm in the process of modding the dials with blue leds hehe.

.logic.

po0k

how much did that set you back?
Order it from 'foreign'??

There's something about making it yourself....taht first time you shock yourself after leaving the +12V line touching teh earthed case. You boot up and stroke the case fondly, before recoiling instantly and knocking your pride and joy off a 4' table edge.

It's teh buzz I live for.