The WOPL Cooling Fan Thread

[laatsch55]

So, we have a Snap-on cooling fan, but it is not temperature controlled. I have looked and there are a lot of options. I'm hoping Joe chimes in with a simple PWM based control method...

 

[Gepetto]

So, we have a Snap-on cooling fan, but it is not temperature controlled. I have looked and there are a lot of options. I'm hoping Joe chimes in with a simple PWM based control method...

I'll look around Lee and see if anything is available off the shelf.

 

[jbeckva]

Hey what about something based on this?

http://www.micrel.com/_PDF/mic502.pdf

 

[Gepetto]

Hey what about something based on this?

http://www.micrel.com/_PDF/mic502.pdf

Sure you can go that way, was looking for a packaged and ready to go controller for this however.

Most quality fans these days have 4 leads. 12V, GND, Tacho and PWM input. Was surfing for a packaged controller that took advantage of this.

 

[NavLinear]

Have you guys found a cooling "system" that you're comfortable with? Kinda curious.

 

[Zach C.]

Have you guys found a cooling "system" that you're comfortable with? Kinda curious.

I've been looking to build something like this, too.

I don't really want an off the shelf solution, though- Would rather assemble myself...but whatever works

Lee mentioned, some time back, that Joe had linked to a PWM design, but I could never find it on this board.

Been meaning to ask about that...

I did a little digging around on the web, but didn't go real far with it (been busy). It looked like most would need a 12V supply, which would almost require a switching supply, or huge waste of energy/ heat sinking with a linear supply unless I'm wrong...

I can't believe I missed this thread until now.

 

[Northwinds]

The fan setup Jer made me works very well. Granted it's not temperature controlled but I have it plugged into another component I don't use and when things start getting warm, I just flip the switch and the dual fans do their job quickly and efficiently. I did see an PL400 auction Lee posted with the same type fans but were bolted through the fins via threaded rods with holes drilled through the fins. Pretty neat idea that disassembles quickly if you need access to the drivers

 

[laatsch55]

I'm still partial to my snap-ons...

 

[laatsch55]

Was talking to Stephen last nightand he remembers an acoustical-coupled fan back iin the day, where as you turned up the volume so did the fan speed....

 

[Northwinds]

Was talking to Stephen last nightand he remembers an acoustical-coupled fan back iin the day, where as you turned up the volume so did the fan speed....

That sounds interesting... so at idle they don't move but when you push the gas pedal they do their thing based on need. Pretty nifty!

 

[laatsch55]

And may perhaps answer the anticipation aspect of keeping the semiconductors to a narrower range of temp to eliminate a heating/cooling cycle which if not destructed by overdriving is the number one cause of failure, not electical, but mechanical in nature...

 

[Zach C.]

Was talking to Stephen last nightand he remembers an acoustical-coupled fan back iin the day, where as you turned up the volume so did the fan speed....

Interesting idea, but temp still seems better to me. Calibrate once, and you're done.

With acoustical, every time you change speakers, rooms, location it would change.

OTOH, stuff with big dynamics then near silence would be improved.

Potentially abuse the gear or bask in the glow of audiophile nirvana?

Also, what audiophile doesn't want one more thing to tweak?

Guess it depends on whether you like metal or classical.

 

[laatsch55]

As it stands at my place, I turn my tunebox on listen to a couple at mid volume, get things warmed up then plug the fan in..

 

[CASSETTE DECK]

So, we have a Snap-on cooling fan, but it is not temperature controlled. I have looked and there are a lot of options. I'm hoping Joe chimes in with a simple PWM based control method...

I have just designed a pulse width modulated fan speed controller.

> All discrete components, no integrated circuits. Silicon transistors only.
> Adjustable frequency.
> Adjustable temperature.
> Wide operating voltage range.
> Uses NTC thermistor, PTC thermistor or transistor for heat sensing.
> Highly sensitive, accurate.
> Operates fan at any speed up to maximum speed at rated voltage.
> Low cost.

I tested the fan speed controller on an adjustable voltage regulated power supply.
I set the prototype at 25 degrees centigrade. Fahrenheit???

This circuit will have other uses including an all discrete PWM switchmode controller, motor speed controller and DC dimmer.

 

[laatsch55]

Well post the schemo CD!!

 

[CASSETTE DECK]

Well post the schemo CD!!

I will be posting a schematic soon.

 

[laatsch55]

OK...

 

[CASSETTE DECK]

Schematic: Temperature controlled PWM fan speed control.



EDIT 1: A 100nF ceramic capacitor must be connected across the power supply to maintain stability due to RF noise generated by fan motor.

EDIT 2: A 100nF ceramic capacitor must be connected between positive and base of PNP transistor with thermistor and resistor in series. This helps to prevent RF oscillation in the differential amplifier.
1K ohm resistor in series with thermistor changed to 1K5 to raise temperature.
1K ohm resistor on emitters of PNP differential amplifier changed to 470 ohm to increase frequency and bias current.
330 ohm 0.5 watt resistor on collector of BC337 driving TIP41 changed to 150 ohm 2 watt to increase drive current for high power DC fans.
330 ohm 0.5 watt resistor on collector of other BC337 changed to 620 ohm 0.5 watt to reduce power consumption when fan is not operating.

EDIT 3: Timing capacitors changed from 10uF to 2.2uF to bring start-up frequency closer to 30Hz.
Choke with iron powder core connected between positive of fan power supply and speed controller power supply. Inductance not critical. 50 turns 2cm core diameter.
1000uF electrolytic capacitor and 100nF ceramic capacitor connected across fan power supply.

 

[laatsch55]

I love the discreet nature of it...

 

[CASSETTE DECK]

I love the discreet nature of it...

I prefer to use discrete designs whenever possible.
Nothing much to it, just a PNP differential amplifier direct coupled to an NPN astable multivibrator, driving a miniature power transistor to control fan speed with a pulse width modulated low frequency.

All common silicon transistors. Economical, flexible design, can be modified to use PTC thermistors and semiconductors for heat sensing. Easy to adapt for other applications.

A change in temperature causes the differential amplifier to go out of balance, which can shut the fan off completely, run it at full speed 100% duty cycle or any speed in between.

The frequency is adjusted by changing the value of the timing capacitors or common emitter resistor of differential amplifier.
The temperature is adjusted by changing the value of resistor in series with NTC thermistor.