12Vdc Fan Speed Controller.........

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Janitor Tzap
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12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

Well, here's my problem.

I had a bunch of crappy sleeve bearing fans fail on me, in one of my computers.
So, I replaced them with good quality ball bearing fans.

One of these 12Vdc fans is a;
SUNON PMD1208PMB1-A
5700 RPM
84.1CFM
9.1Watt.
It really keeps the CPU cool, only it is really loud!

I have tried using the on board fan speed controller on the Mother Board to adjust the fan speed.
But it doesn't have very good control over this one fan.

After taking the SUNON Fan and connecting it too my variable bench power supply.
I found a voltage of around 7 - 7.5 Volts provides enough air movement for adequate cooling,
and isn't so loud, that it drowns out someone talking normally.

I've come across circuits for fan controllers.
Here's one of the simplest;
Image
Only I have run into a hitch.
The TIP122 (or NTE261 equivalent) is something I don't have. :(
So, I'm wondering if I could use a different transistor in it's place?
{I currently got quite a few 2N3055's and BU806's.}


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dacflyer
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Re: 12Vdc Fan Speed Controller.........

Post by dacflyer »

any npn should work so long as it can handle the current draw, if possible use one that is good enough that you do not need a heatsink.
otherwise use one if you got the space, or mount it to the case, just make sure it is insulated.
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Re: 12Vdc Fan Speed Controller.........

Post by dyarker »

The TIP-122 is an NPN Darlington, while the 2N3055 is a single NPN power transistor. So no, not a direct replacement. However, if you connect a 2N2222, or similar, transistor to the 2N3055 in a Darlington configuration, then yes they (together) will substitute.

Connect the collectors of the 2N2222 and 2N3055 together. This becomes the Darlingto collector.

Connect the emitter of the 2N2222 to the base of the 2N3055, and to nothing else.

The emitter of the 2N3055 is the emitter of the Darlington combination.

The base of the 2N2222 is the base of the Darlington combination.

You may need to increase the base resistance because the min gain of a TIP-122 is 1000, while the min gain of the 2N2222 and 2N3055 together in Darlington is 2000.

Cheers,
Dale Y
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Re: 12Vdc Fan Speed Controller.........

Post by Externet »

I have only a fixed value 5W series resistor in my PC fan tailored to the quietness and fanning I want.
- Abolish the deciBel ! -
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Re: 12Vdc Fan Speed Controller.........

Post by dyarker »

Just looked up BU806. It is a Darlington, but the gain is 1/10 that of the TIP-122. Using this might require you add a 2N2222 , or similar, anyway, making a double Darlington.

Which ever you choose, monitor the temperature at first, might need a small heatsink.

A power resistor is, of coarse, another way to do it. But power resistors aren't cheap, and you say you have transistors on hand.

Cheers,
Dale Y
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Re: 12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

UPDATE:

While digging in my dead board piles, I spied a TIP 121.
I checked if it was the same as the TIP 122.
It was!

But after bread boarding the circuit, and testing the fan with it.
The fan was still running to fast.
I checked the voltage at the fan.
The voltage at it's lowest was 10.5V, and highest 11.7V.

I then changed 10K potentiometer for a 100K potentiometer.
Now I can completely shut off the fan, by bringing the voltage all the way down to 1.5V.
The fan is almost full on, by bring the voltage up 11.8V.

Okay,
Now I just have to work out how to construct it on a PCB,
and put 3Pin Male & Female connectors on it.


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Re: 12Vdc Fan Speed Controller.........

Post by dyarker »

Nice bit of luck finding a TIP-121. Using potentiometer as a potentiometer instead of variable resistance would have reduced problems caused by different gains of different transistors (even same part number) and different impedances of different fans.

C U L
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Re: 12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

UPDATE:

Well,
I've got the speed controller assembled, and it works just fine. :)

Only I'm kicking myself for throwing out the big box of knobs I had.
{I never thought I was ever going to need one.} :(
Because the price for just a knob is NUTS!
They range from 2 dollars for a simple plastic knob,
up to 20 dollars for a brushed aluminum knob!
Guess I'll go dumpster diving, or hit some of the old electronic shops that are still around.

I also decided to add a 0-20V Digital Panel Meter.
So, I can monitor the voltage to the fan.
Image
{I could of gone with a dirt cheap Digital Panel Meter for a dollar, but I wanted one with the bezel.
Thus, it would look nicer when I mount it on to one of the 5 1/4 plastic bay covers.}



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Re: 12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

UPDATE:

Well,
The 0-20V Digital Panel Meter arrived today.
Image
But it has a 4 wire hook up.
Red
Black
Blue
Yellow
Red & Black are the 8Vdc to 12Vdc Power input.
Blue & Yellow are the test leads.
Yellow is Positive.
Blue is Negative.

But I'm hesitant to try it in the Fan Circuit.
Because I'm planning to power the Panel Meter from the 12Vdc line.
Could I tie the Blue & Black wires together without having it burn up?

This came from YB Electronics Co., LTD in China.
No Data Sheet.
Just some Kanji on the side of the box. :(


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Re: 12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

UPDATE:

Well,
After playing E-mail tag with YB Electronics for a several days.
I'm giving up trying too exchange the Panel Meter, for a 3 wire version that will work in my fan circuit. :mad:

Because the 0-20V Digital Panel Meter is a 4 wire hook up.
Red
Black
Blue
Yellow
Red & Black are the 8Vdc to 12Vdc Power input.
Blue & Yellow are the test leads.
Yellow is Positive.
Blue is Negative.
I have to isolated the Panel Meter from the 12Vdc Supply.
Thus, I'm going to build a Isolated 9Vdc Supply for it.

I found a fairly simple one.
Image
Only need one component to finish it.
Any one got a 750 ohm 5% or 1% Tolerance 1/2Watt Resistor they'd like to part with?



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Re: 12Vdc Fan Speed Controller.........

Post by dacflyer »

have you not tried to combine more than 1 resistor to get the value you need ?
such as a 560 + 190 = 750
or use a small trim pot like a 1K and adjust it down to 750.
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Re: 12Vdc Fan Speed Controller.........

Post by Janitor Tzap »

dacflyer wrote:have you not tried to combine more than 1 resistor to get the value you need ?
such as a 560 + 190 = 750
or use a small trim pot like a 1K and adjust it down to 750.
Yeah, I thought of doing two resistors together.
But of course I couldn't find any 190 ohm resistors.

I've got some trim pots, 10 turn, 15 turn, and some 25 turn trimmers.
But I need to look through them. :P

Though I kinda want too keep the circuit simple, and small.
I'm thinking mounting it on to the back of the Digital Panel Display.
Image
Using the 4-pin socket too piggy back the Isolated 9Vdc Supply on to it.



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Re: 12Vdc Fan Speed Controller.........

Post by dyarker »

A 1/2W trim pot? Really?
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Re: 12Vdc Fan Speed Controller.........

Post by Engineer3104 »

How about using two 1.5k ohm 1/4 W in parallel?
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Re: 12Vdc Fan Speed Controller.........

Post by dyarker »

Yes fine, if you leave air space between them. It was "small trimpot" as replacement for 1/2W resistor that caught my eye. Those things are 1/4W or less, and would not last long dropping power.
Dale Y
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