rheostat instilation?

Ok so i went to radioshack to buy a rheostat, aparently it wasnt big enough or i installed it wrong because it melted right up.

Can someone give me a link to a cheap rheostat as well as instructions to installing it please :-(.

Try Search or Google it. 1st try on Google:
GUIDE LINK
THE FANMAN

I'm going to try and make this as nice as possible, i've read 3 posts you've made and everytime your under the assumption that the person has done no research on the topic. This is not always the case. I'd prefer a rheostat as it's an easier installation.

Thank you for the link though i'll read it over and see if i could handle making something like that.

??????????????

Are you still interested in a good rheostat and how to install it?

yes...

Here is a good Rheostat and it's very cheap. It is also has a high wattage rating to keep it from burning out with high wattage fans. I am using one with a 9 watt Tornado fan and it works great. The only problem you might have is if you run the fan too slow in rpms. It might not start the next time you turn your PC on, but this will happen with any Rheostat unless the fan has a very low starting voltage. This Rheostat is only rated for 15 Ohms so your not gonna do much better then that with the starting issue. So have it turned to around a 1/4 turn for the fan to start when you turn on the PC. With this Rheostat my Tornado runs from around 3300 to 5700. Here is the link;

http://www.allelectronics.com/cgi-bin/category.cgi?category=470&item=RHE-15&type=store


To connect the Rheostat you use it with the RED or YELLOW wire from a fan. The Positive voltage wire. If you look at the rheostat there are 3 connections. You want to solder the middle to one of the side connections, it doesn't matter which one.

You want to cut the red or yellow wire from the fan in half, and solder one end of the wire to the two connections you soldered together on the Rheostat and the other end of the wire to the single connection on the Rheostat.

FYI its not really a Rheostat. A Rheostat has only two connections. Its a potentiometer that your converting to a Rheostat. You really only have to use 2 connections for it to work. The middle and either side connection, but in electronics your not suppose to leave a connection that goes no where. Thats why you solder one side connection to the middle connection.

15W pot will handle any combination of fans that pulls 60w full speed.

Crull are you sure about that

the yellow wire is the rpm sense wire and i doubt you need to be messing with that

from my knowlege of electronics you just nead a resitor in series with either the + or - power lines to the fan

if you have a 12v fan that uses 1.8 w and .15a it has a resistance of 80ohms

V=I*R

if resistors are in series you add up the total resitance devide the voltage by that

Rtotal=R1+R2

Vtotal/Rtotal=v

if you take that little v times the resistance of each of the resitors you get how many volts each gets

v*R1=V1 v*R2=V2

and V1+V2=Vtotal all the sub voltages will ad up to the total

so if i put a 20ohm resistor in series with a 80ohm fan

Rtotal=20+80=100
Vtotal/Rtotal = 12/100 = .12 = v
v*r1 = .12*20=2.4v = the little resitor gets 2.4v
v*r2 = .12*80=9.6v = your fan is running on 9.6v

A pot just changes resitance from 0 to a maxium

figuring out the wattage for your pot is somthing beond me just get a big one and if it melts you out $2 and get a bigger one

Sorry about that Bluestreak,Here's a good guide on your project.
Please save the link,as there are numerous guides at this site.
THE FANMAN

GUIDE LINK

Dont get mad.This is what I found at the forum by putting
"wiring fans" in the search box.Check it out Dood.
SEARCH RESULTS

Thanks crull i found that one yesterday. Can you show me a picture by any chance of what it lokos like setup?

the yellow wire is the rpm sense wire and i doubt you need to be messing with that

Click to expand...

He was refering to the other yellow wire

zebkoolindc said:

Crull are you sure about that

the yellow wire is the rpm sense wire and i doubt you need to be messing with that

from my knowlege of electronics you just nead a resitor in series with either the + or - power lines to the fan

if you have a 12v fan that uses 1.8 w and .15a it has a resistance of 80ohms

V=I*R

if resistors are in series you add up the total resitance devide the voltage by that

Rtotal=R1+R2

Vtotal/Rtotal=v

if you take that little v times the resistance of each of the resitors you get how many volts each gets

v*R1=V1 v*R2=V2

and V1+V2=Vtotal all the sub voltages will ad up to the total

so if i put a 20ohm resistor in series with a 80ohm fan

Rtotal=20+80=100
Vtotal/Rtotal = 12/100 = .12 = v
v*r1 = .12*20=2.4v = the little resitor gets 2.4v
v*r2 = .12*80=9.6v = your fan is running on 9.6v

A pot just changes resitance from 0 to a maxium

figuring out the wattage for your pot is somthing beond me just get a big one and if it melts you out $2 and get a bigger one

Click to expand...

When I said yellow my mind was thinking of the 12+ yellow wire in the molex connector that the fans positive wire goes to and it usually is red. Sorry about that. Fans don't always stick to color codes. Yes, yellow is usually the sense wire, but I have also seen it blue.

Thats right the rheostat is in series with the positive wire from the fan. The Rheostat creates a voltage drop, so less voltage for the fan.

Usually any Rheostat under around 100 Ohms will work with most of the cooling fans out there. If the fan is high wattage, then you need a high wattage rheostat.

I can draw you a picture, but I am not sure how to post it here. Give me your Email and I will send it to you OK?

Didn't know I could attach files here until now. Here is a picture of how to attach the rheostat. I didn't draw the connector on the end of the wires, because that stays the same. The wires don't change position in the connector.

thanks, my setup was way wrong...that would explain why it went up in smoke so quickly lol

Your welcome. Like I posted before it doesn't matter which side connector you use with the middle connector on the rheostat. So connect the middle with either side connector on the rheostat. Now when you connect the postive fan wires to the two connections on the Rheostat, that will determine which direction the knob will turn to go from min rpm's to maximum rpm's. Clockwise or counter clockwise. Hope that makes sense.