Rheostats?

Avathar77

Avathar77

Avathar77

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I am making a fan controller from scratch. Nothing fancy, just some switches and buttons. Mainly because I dont like all the led lights in many of fan controllers in the market and I already had some toggle switches hiding in my goodies cupboard :D
Right now I am controlling the RAD fans and side fan by motherboard headers, but would like to include this to the custom fan controller as well.
Problem is finding some rheostats so that I can adjust the speed. I tried looking in a high street electrical store but they don't sell them any more!

So any one have any idea where I can get my hands on some Rheostats? I need about 5 of them(20-50 ohm).

At the moment it looks like this

DSC01214.jpg


There are 9 toggle switches (I know it looks like over kill but thats all the toggle switches I had!) and 2 push to make switches for the LEDs inside the case.
 
Always used ****** for stuff like that in the past...online webby not hard to find & they have quite a few stores all over the place. Would agree with potentiometers too :)
 
Always used ****** for stuff like that in the past...online webby not hard to find & they have quite a few stores all over the place. Would agree with potentiometers too :)

oh an edit.....seems the electronics store is censored here.

two posts....dunno how that happened but they're both free....even if now useless :\
 
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Be mindful of the low current handling of potentiometers. Typically a voltage reduction circuit used for fans will consist of a transistor that directly controls the fan with a potentiometer to control the transistor.

I had no luck finding Rheostats either.

I never got around to making a fan controller, although I did look at several methods including a nifty 3 pin linear PWM design and also a diode based rotary switch design.

Was thinking of making an external desk mounted box too.
 
Pay attention to the power rating on those pots. Make sure any fans you wire up, doesn't exceed the power rating, it'll be in Watts.
 
found some articles which suggests using a transistor or a mosfet, while others just instructs to connect the fan and potentiometer.
I was going to control 2x Noctua NF-S12B's(http://www.overclockers.co.uk/showproduct.php?prodid=FG-006-NC&groupid=701&catid=57&subcat=4) which will be attached to the second RAD I will be putting soon.

Fans are rated at 1.2 W, 0.1A @12V
http://www.noctua.at/main.php?show=productview&products_id=25&lng=en&set=1

after some calculations I think I need 10watt, 200ohm potentiometers.

I am not much of a electronics guy, so have to do some reading before doing this. Any advise will be appreciated.
 
CD32 said:
Always used ****** for stuff like that in the past...online webby not hard to find & they have quite a few stores all over the place. Would agree with potentiometers too :)

oh an edit.....seems the electronics store is censored here.

two posts....dunno how that happened but they're both free....even if now useless :\
Click to expand...

Can you pm me the place where you were thinking of? If it is the high street electrical store I am talking about then I have tried and they dont do Rheostats but they do have potentiometers.

panyan said:
good man! show the manufaturers how they should be done! they put LED's in everything!

cant wait to see if it works nice :)
Click to expand...

Don't get your hopes up yet!:D
 
Using a LM317T you could make a simple circuit so you could use a potentiometer. Potentiometers are not designed to drive fans directly, they just don't have the current capacity, they usually have as low rating of about 0.25W. Which is not going to be enough even for your 1.2W fans.

facpltxray.gif


The LM317 as far as I recall drops the voltage by 1.5v. Other transistors and mosfets have lower drops but I've seen 317 used a lot in DIY circuits because it is very cheap. The LM317T also supports a large current rating more than enough for a few fans.
 
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Thanx guys for the replies!


PhillyDee said:
You could make an inexpensive PWM controller out of 555 timers.
http://www.nomad.ee/micros/pwm555.html
I have made similar ones in the past and they work a treat.

Just some soldering required!
Click to expand...

Got your PM, but the above link is a bit 2 complicated for me :o

Tealc said:
Using a LM317T you could make a simple circuit so you could use a potentiometer. Potentiometers are not designed to drive fans directly, they just don't have the current capacity, they usually have as low rating of about 0.25W. Which is not going to be enough even for your 1.2W fans.


facpltxray.gif


The LM317 as far as I recall drops the voltage by 1.5v. Other transistors and mosfets have lower drops but I've seen 317 used a lot in DIY circuits because it is very cheap. The LM317T also supports a large current rating more than enough for a few fans.
Click to expand...

I have couple of zalman fan mate2's and after taking one of them aprt, i can see the layout is just about the same as the above diagram except for the led and one of the resistors.
If I can take out the rheostat/potentiometer in fanmate2 by de-soldering , May be I can extend it to the drive bay.
 
Avathar77 said:
Can you pm me the place where you were thinking of? If it is the high street electrical store I am talking about then I have tried and they dont do Rheostats but they do have potentiometers.
Click to expand...

er I can't seem to find how to send a pm :confused:
 
PhillyDee said:
There is only trust. You may have to activate yours first. It gives you acess to the MM (see FAQ for details)
Click to expand...

ok tnx for that....think I did a trust thing ages ago to access the market thingy...anyway will see what happens when I press trust..

(altho the place only lists potentiometers on it's online webby too)
 
Tealc said:
Using a LM317T you could make a simple circuit so you could use a potentiometer. Potentiometers are not designed to drive fans directly, they just don't have the current capacity, they usually have as low rating of about 0.25W. Which is not going to be enough even for your 1.2W fans.

facpltxray.gif


The LM317 as far as I recall drops the voltage by 1.5v. Other transistors and mosfets have lower drops but I've seen 317 used a lot in DIY circuits because it is very cheap. The LM317T also supports a large current rating more than enough for a few fans.
Click to expand...

Got a question, I am a bit of a noob when it comes to electronics, but need some help with one of the diagrams you attached.
In yours there is a LED, if I to remove the LED would it be correct to assemble it like this?
DiagWithOUTLED.jpg


Also there are 2 types of 240ohm resisters I can find, one is carbon film and the other metal film, would either be ok or not? Also sent some links in trust, can you please have a look?
 
Either type of resistor is just fine, whichever is cheaper basically.

Don't forget you'll need the Potentiometer as well though which will control the voltage that the fan sees.

A heatsink will just be small slab of metal with a hole in it for a screw to fit through. Apply some thermal paste to the rear of the transistor to aid in the thermal transfer. Expect the heatsink to get hot, especially if you have a powerful fan fitted and have it slowed down a fair bit.

If you have 0.3A fan running at 5v it will need to dissipate about 2 Watts of heat, plus whatever the Transistor needs to operate and from what I understand the cheap LM317T isn't particularly efficient. If you load more than one fan to the circuit you'd get more and more heat needing to be dumped so may need to add some surface area to your heatsink.
 
Thank you very much for the reply. So I take it that my removing of the LED and 180ohm resister is ok?
I have some aluminium strips that can be made in to DIY heat sinks.

I have an idea about the Potentiometer as well.
IMAG0181.jpg

This is from the stock antec front fan. I have 3 of them doing nothing and going to get 2 more from ocuk for 99p each.
All the others I found in the high street shop and online are bit bulky! So thinking of salvaging the Potentiometers out of these antec fans.

I am going to have 5 Potentiometers. 3 of them controlling dual fans(2 rear case fans, 2 fans for RAD1, 2 fans for RAD2) and the remaining 2 Potentiometers controlling 1 fan each.

I found some LM317T's and 240ohm resisters in the bay(I have trust mailed you the links) but as you said I might have to get some good ones!
 
The LED would serve as an indicator of the relative amount of voltage running through the circuit, the 180 ohm resistor was just there to pull down the voltage enough that it didn't fry itself. Removing that circuit will have no effect on the function of the circuit as a voltage regulator.

And the 317T you linked should be fine.

Not sure about those pots you have though. My Tri-cools are switched with a little three position switch. Do you have any idea of the resistance of those Pots? They could be very different from what you need. Measure the maximum resistance and the minimum resistance to determine whether they'll work. If the resistance is too low you'll lose the ability to adjust the speed sufficiently and if it's too high then you'll find that even the slightest of tweaks will cause your fans to come juddering to a halt. The National semiconductor datasheet calls for a 5k potentiometer so I'd get one of those to try out but I might be tempted to grab a 2k one as well just to see if I got better range off it. After all the LM317T is rated for as much as 37v output.
 
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