Controlling three fans with one knob?

[MichaelD]

My case has three 120mm fans. They are currently 3-speed Antecs but I am willing to replace them, possibly even with the 120CFM monsters that came with the case.

What I want is a single knob with which I can control the speed of all three fans at the same. I want to go from a very slow speed all the way to full with the same knob.

I'm handy with a soldering iron and heat shrink so modding is not a problem.

I don't want a bay controller with 20 different knobs; I want to put the single knob on a PCI slot cover.

If it cannot be done with one knob, I'd be willing to go to three knobs (one per fan) with the same granular control. I can fit three mini-pots on a single PCI slot cover.

Can this be done?


Thanks!

 

[DerwenArtos12]

Evening Michael.

What's the full-speed wattage on the antecs?

 

[MichaelD]

Hi there, DA.

The full speed wattage of the Antecs is 2.9 watts EACH (8.7 total)
The full speed wattage of the stock fans is 9.6 watts EACH (28.8 total)

Big diff b/t those two fans, I know.

Basically, I'm looking for this exact thing, but it can control 3 fans simultaneously.

Thanks man!

 

[DerwenArtos12]

Originally posted by: MichaelD
Hi there, DA.

The full speed wattage of the Antecs is 2.9 watts EACH (8.7 total)
The full speed wattage of the stock fans is 9.6 watts EACH (28.8 total)

Big diff b/t those two fans, I know.

Basically, I'm looking for this exact thing, but it can control 3 fans simultaneously.

Thanks man!

I'd say go to your local electronics store or go online and grab 3 50ohm 10W single turn wire-wound potentiometers. You could use just one to control all three antecs or one each for the stock fans. 50 ohms should run them just about into the ground.

 

[MichaelD]

Thanks, DA. Pots have three connections. How would I hook up the fans/power to the pot?

Could I buy a 30w (or greater) pot and control all three stockers with that one pot?

 

[DerwenArtos12]

Originally posted by: MichaelD
Thanks, DA. Pots have three connections. How would I hook up the fans/power to the pot?

Could I buy a 30w (or greater) pot and control all three stockers with that one pot?

you'll want to keep it pretty close to 30w but, keep in mind that a 30W pot is going to be BIG. probably too big to put in an expansion slot plus, the wirewound put off a little RF at 10W so, I'd be hesitant to put it too close to anything too important like a video card.

As far as hooking them up. Your output will be the center terminal and you'll have to pick which of the side terminals you want to use for your input. With the nob facing you, the left will be clockwise to increase ohm and the right terminal will be the oposite.

 

[MichaelD]

Thanks much. I didn't know about the pot putting out RF; that's definitely an important consideration.

I'm still confused how to hook everything up. Power, fan, pot...what goes where?

 

[DerwenArtos12]

Originally posted by: MichaelD
Thanks much. I didn't know about the pot putting out RF; that's definitely an important consideration.

I'm still confused how to hook everything up. Power, fan, pot...what goes where?

Oh, you'll want 12v into the pot(right side with the knob facing you), then into the fan(from the center terminal of the pot), then back to a ground from the fan. That'll have it so clockwise will decrease resistance and increase fan speed.

EDIT: oh god, I'm being dumb this morning. Just realized I wrote RF instead of EMF, sorry.

 

[jdkick]

I'm wondering if something like this could be helpful along the way. I just woke up tho, so I don't have any bright ideas at the moment.

 

[DerwenArtos12]

Originally posted by: jdkick
I'm wondering if something like this could be helpful along the way. I just woke up tho, so I don't have any bright ideas at the moment.

I'm not sure if that was a compliment or an incomplete thought but, I'll assume it's a compliment.

Thanks.

 

[jdkick]

lol. That's what I get for posting early in the morning. I forgot to add the link:

http://www.sunbeamtech.com/PRO...an-power-port/mfpp.htm

 

[DerwenArtos12]

Originally posted by: jdkick
lol. That's what I get for posting early in the morning. I forgot to add the link:

http://www.sunbeamtech.com/PRO...an-power-port/mfpp.htm

ah, not especially. it only works properly at 12V due to the layout of the internal circuit board. Quite frankly you could just as easily buy some of these or even some of the basic white ones for even cheaper and wire up as many fans as you wanted to the pot or, as I've done before, wire the pot inline with a pair of male molex connectors then wire up a 4 pin female molex connector with as many 3 pin connectors as you want. I usually use both ground wires when making custom connectors like this so that you cannot accidentally plug this into any drives and feed it funny voltages or voltages through a ground. Just id10t proof it a little.

 

[MichaelD]

Originally posted by: DerwenArtos12

Originally posted by: MichaelD
Thanks much. I didn't know about the pot putting out RF; that's definitely an important consideration.

I'm still confused how to hook everything up. Power, fan, pot...what goes where?

Oh, you'll want 12v into the pot(right side with the knob facing you), then into the fan(from the center terminal of the pot), then back to a ground from the fan. That'll have it so clockwise will decrease resistance and increase fan speed.

EDIT: oh god, I'm being dumb this morning. Just realized I wrote RF instead of EMF, sorry.

Does the ground from the fan go to the third (leftmost with knob facing me) terminal on the pot? Sorry for all the questions...don't wanna blow anything up.

 

[Zepper]

Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

 

[MichaelD]

Originally posted by: Zepper
Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

Thanks for the ideas. I'm not real good (OK, I have no idea) how to spec out the wattage/ohmage of resistors and the like. Any ideas on how I could do that? For example: How did DarwenArtos12 figure I needed 50-ohm, 10watt pots?

 

[DerwenArtos12]

Originally posted by: MichaelD

Originally posted by: DerwenArtos12

Originally posted by: MichaelD
Thanks much. I didn't know about the pot putting out RF; that's definitely an important consideration.

I'm still confused how to hook everything up. Power, fan, pot...what goes where?

Oh, you'll want 12v into the pot(right side with the knob facing you), then into the fan(from the center terminal of the pot), then back to a ground from the fan. That'll have it so clockwise will decrease resistance and increase fan speed.

EDIT: oh god, I'm being dumb this morning. Just realized I wrote RF instead of EMF, sorry.

Does the ground from the fan go to the third (leftmost with knob facing me) terminal on the pot? Sorry for all the questions...don't wanna blow anything up.

no, the ground from the fan would just go to ground. I'll get a picture up of one I have here for fan testing that uses a pair of 10W 25 ohm pots for more precision. I basically ran it 12v>pot>pot>3pinconnector so that the 12v went in the left terminal, out the center, in the second pot left terminal, out the center terminal to a 3 pin fan connector center pin, then a wire from the ground on the 3 pin straight back to the ground on the molex. I'll get a picture up this evening.

 

[MichaelD]

Originally posted by: DerwenArtos12

Originally posted by: MichaelD

Originally posted by: DerwenArtos12

Originally posted by: MichaelD
Thanks much. I didn't know about the pot putting out RF; that's definitely an important consideration.

I'm still confused how to hook everything up. Power, fan, pot...what goes where?

Oh, you'll want 12v into the pot(right side with the knob facing you), then into the fan(from the center terminal of the pot), then back to a ground from the fan. That'll have it so clockwise will decrease resistance and increase fan speed.

EDIT: oh god, I'm being dumb this morning. Just realized I wrote RF instead of EMF, sorry.

Does the ground from the fan go to the third (leftmost with knob facing me) terminal on the pot? Sorry for all the questions...don't wanna blow anything up.

no, the ground from the fan would just go to ground. I'll get a picture up of one I have here for fan testing that uses a pair of 10W 25 ohm pots for more precision. I basically ran it 12v>pot>pot>3pinconnector so that the 12v went in the left terminal, out the center, in the second pot left terminal, out the center terminal to a 3 pin fan connector center pin, then a wire from the ground on the 3 pin straight back to the ground on the molex. I'll get a picture up this evening.

Thanks very much for the pic; I'm a totally visually-oriented person. If I see it, I can figure it out.

 

[DerwenArtos12]

Originally posted by: MichaelD

Originally posted by: Zepper
Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

Thanks for the ideas. I'm not real good (OK, I have no idea) how to spec out the wattage/ohmage of resistors and the like. Any ideas on how I could do that? For example: How did DarwenArtos12 figure I needed 50-ohm, 10watt pots?

That would depend entirely on the fans. Thats why I said one pot for all three antecs or one pot per the stock fans. You just use ohms law that states resistance = voltage / amperage. For figuring out what reistance you want you just plug in your fans amperage and what you want the change in voltage to be. IE if you want to run the fan at 3 volts it would be R=9/.25 so you want a 36 ohm resistor rated at the total wattage of the fan. Then you use a color code calculator to figure out what color band resistor you're looking for cause I can't even remember what the codes are and thats telling us you need an orange blue black.

 

[MichaelD]

Originally posted by: DerwenArtos12

Originally posted by: MichaelD

Originally posted by: Zepper
Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

Thanks for the ideas. I'm not real good (OK, I have no idea) how to spec out the wattage/ohmage of resistors and the like. Any ideas on how I could do that? For example: How did DarwenArtos12 figure I needed 50-ohm, 10watt pots?

That would depend entirely on the fans. Thats why I said one pot for all three antecs or one pot per the stock fans. You just use ohms law that states resistance = voltage / amperage. For figuring out what reistance you want you just plug in your fans amperage and what you want the change in voltage to be. IE if you want to run the fan at 3 volts it would be R=9/.25 so you want a 36 ohm resistor rated at the total wattage of the fan. Then you use a color code calculator to figure out what color band resistor you're looking for cause I can't even remember what the codes are and thats telling us you need an orange blue black.

:thumbsup: Ah, I see now. Thanks for sharing the knowledge and the link. I never took any electronics courses...can you tell? :laugh:

 

[Zepper]

You could just use the circuit of one channel of the Sunbeam Rheobus with a heavier duty transistor capable of 3A current - very simple circuit - one power transistor, one resistor (two if you want to lock in a minimum voltage), one light-duty pot.

.bh.

 

[Martimus]

Originally posted by: DerwenArtos12

Originally posted by: MichaelD

Originally posted by: Zepper
Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

Thanks for the ideas. I'm not real good (OK, I have no idea) how to spec out the wattage/ohmage of resistors and the like. Any ideas on how I could do that? For example: How did DarwenArtos12 figure I needed 50-ohm, 10watt pots?

That would depend entirely on the fans. Thats why I said one pot for all three antecs or one pot per the stock fans. You just use ohms law that states resistance = voltage / amperage. For figuring out what reistance you want you just plug in your fans amperage and what you want the change in voltage to be. IE if you want to run the fan at 3 volts it would be R=9/.25 so you want a 36 ohm resistor rated at the total wattage of the fan. Then you use a color code calculator to figure out what color band resistor you're looking for cause I can't even remember what the codes are and thats telling us you need an orange blue black.

If you want to use a 10W pot you could create a simple parallel circuit so that the resistorswill take 2/3 of the load, while the Pot would still stay at 10W, and the whole circuit would have the power characteristics that you want (30W like you stated). Also, I wouldn't hook the Pot directly between the 0 and 12V line. It would be better to first figure out the effective range of the fans, then build your circuit to just operate at those ranges, so you don't accidentally turn all of the fans off when you don't want to. Just build a simple voltage divider circuit with the Pot on the top end (the effective range) of the circuit, and you will be all set!

 

[DerwenArtos12]

Originally posted by: Martimus

Originally posted by: DerwenArtos12

Originally posted by: MichaelD

Originally posted by: Zepper
Well, you could use a 4-position rotary switch (may want to drill a hole in the case for the switch and three resistors patched into the 12V lead from the PSU to give you control of the three fans at once via the Sunbeam thingy. Or use the connectors that DA linked and a piece of perfboard to rig your own. Or you could use one heavy duty variable voltage regulator or transistor so your switch and resistors (or pot) could be lower power, more compact and cost less.

.bh.

Thanks for the ideas. I'm not real good (OK, I have no idea) how to spec out the wattage/ohmage of resistors and the like. Any ideas on how I could do that? For example: How did DarwenArtos12 figure I needed 50-ohm, 10watt pots?

That would depend entirely on the fans. Thats why I said one pot for all three antecs or one pot per the stock fans. You just use ohms law that states resistance = voltage / amperage. For figuring out what reistance you want you just plug in your fans amperage and what you want the change in voltage to be. IE if you want to run the fan at 3 volts it would be R=9/.25 so you want a 36 ohm resistor rated at the total wattage of the fan. Then you use a color code calculator to figure out what color band resistor you're looking for cause I can't even remember what the codes are and thats telling us you need an orange blue black.

If you want to use a 10W pot you could create a simple parallel circuit so that the resistorswill take 2/3 of the load, while the Pot would still stay at 10W, and the whole circuit would have the power characteristics that you want (30W like you stated). Also, I wouldn't hook the Pot directly between the 0 and 12V line. It would be better to first figure out the effective range of the fans, then build your circuit to just operate at those ranges, so you don't accidentally turn all of the fans off when you don't want to. Just build a simple voltage divider circuit with the Pot on the top end (the effective range) of the circuit, and you will be all set!

Thats getting kind of complicated for someone who hasn't taken a single electronics course don't you think. I don't think he intends to use this for on the fly adjustments, just to find a happy medium voltage instead of being constrained to 12v, 7v, 6v and 5v.

 

[Martimus]

Originally posted by: DerwenArtos12
Thats getting kind of complicated for someone who hasn't taken a single electronics course don't you think. I don't think he intends to use this for on the fly adjustments, just to find a happy medium voltage instead of being constrained to 12v, 7v, 6v and 5v.

Yeah, you are probably right. I just get a little excited about building circuits now that I don't have access to an electronics lab anymore. I have fond memories of designing and building circuits to do the simple testing functions for me. (While I was never a test engineer, I spent a large portion of my time at my previous two jobs doing system and component level testing) I gave up making my own work lab when I had a baby. (good Oscilloscopes are EXPENSIVE!)

 

[MichaelD]

It's actually kind of embarassing that I've not taken what are today considered "basic" electronics courses. I can read a schematic to a point (anyone remember Heathkit?) I built quite a few of their little amps/sound mixers/radios back in the late 70's/early 80's.

I've also recently assembled speaker crossovers from a parts list and a schematic. I see "how it's supposed to be hooked up" and I can do it. I know the symbols for resistors, caps, diodes, transformers, pots, antenna, etc. I know how to use a DMM (and the analog sweep-needle version!) I just can't do the math b/c I was never trained how to figure that stuff out. I don't build this kind of stuff every day so I don't remember where "power/ground/signal" go by default. My short-term memory is fux0red...what can I say? Gettin' older will do that to'ya.

The reason I'm an active member on these types of forums is to help others and to get help from others. In order to live your life to the fullest, you don't need to know everything; you just need to know WHO KNOWS everything and let them help you.

You guys are smart w/this stuff. I know Exchange and AD...it's a fair trade-off, methinks.

 

[Navid]

Originally posted by: MichaelD
The full speed wattage of the Antecs is 2.9 watts EACH (8.7 total)

If the fan at 12V takes 2.9W, its current is 2.9W / 12V = 0.24A.
Then, you can calculate the effective resistance of the fan to be 12V / 0.24A = 50 Ohms.

If you put the three fans in parallel, the equivalent effective resistance (of the three fan combination) will be 50 Ohms / 3 = 16.7 Ohms.

Let's say you want the fan voltage to go from 12V at max down to 5V at min.
Then, you can calculate the resistance of the pot this way:
When you are at the min RPM (5V), the current will be 5V / 16.7 Ohms = 0.3A.
Then, the resistance in series (variable resistor) must be 7V / 0.3A = 23.3 Ohms.
So, you need a 25-Ohm variable resistor.

The resistor will dissipate the maximum power when its resistance is equal to the effective resistance of the fan (16.7 Ohms). Then, the current is 12V / 2 / 16.7 Ohms = 0.36A.
Then, the max power for the resistor is 6V x 0.36A = 2.16W.
So, go for a 25-Ohm resistor with a power rating higher than 3W to be safe.

The variable resistor (potentiometer) has 3 pins. Short the one in the middle to one of the other two pins and connect the 12V wire to them. Connect the pin at the other end of the resistor to the fans. Connect the other side of the fans to ground.

When you set the resistor to max, the fans will have 5V across them.
When you set the resistor to min (0 Ohms), the fans will have 12V across them.
Or you can have any voltage between 5V and 12V by selecting a setting between min and max.