Are there ventilation devices that can be regulated via voltage or with a resistor?
How do i determine if it has this feature?
>>997633
>Are there ventilation devices that can be regulated via voltage or with a resistor?
You did not state how big of a device you wanted, or exactly how you wanted to control it. But anyway-
1. Most home-ventilation fans are synchronous motors, and varying the speed of them is rather complicated to do. The speed they turn at is dependent on the AC supply voltage frequency.
2. PC fans have brushless motors (which is good, as they last longer than brushed motors) but they have a driver circuit built-in so that they can run right off 12v DC. You can get PC fans from 25mm up to 200mm diameter or so, and motor controllers that will work with DC motors are cheap and simple to use.
3. To adjust the speed of a 12v dc fan, you need a "DC motor controller" that is rated for 12 volts and at least maybe 25%-50% more current that the fan is rated to draw. You can get small DC motor controller boards that have a knob to adjust by hand, or you can get them with "digital" wire hookups that you can operate by an arduino or whatever (5v) microprocessor you want.
4. If you want a fan that can be adjusted manually AND automatically by an arduino, then you run the fan by arduino (using a digital motor controller) and you also have controls hooked to the arduino to tell it what speed you want (there are very cheap + durable capacitive button boards available, with 4 buttons on them). There are motorized pots available but they are kinda expensive, prone to wear and may be difficult to replace in the future.
5. To run a 12v DC motor, you would also need a 12v DC power supply that can deliver at least 2-3 amps. These aren't expensive either. I prefer the ones that have their own metal enclosure over the ones that are a bare circuit board.
6. My own opinion,,,,,,, if you are building electronics projects that plug into a wall socket, it is VERY WISE to put a fuse on them and size it aggressively.
>>997650
Or you could get a four-wire fan, and control it with a voltage-driven PWM signal.
I see how this might have passed you by, given how it only became a standard in 2006 or so.
>>997650
I thank you most respectfully for your extensive answer, despite of the insufficient information provided in my initial post.
I'd work with a 12v DC Fan with about 10 cm diameter, because i'd like to use the same power supply to power LEDs, so in any case i have to get down from the 220V in the network.
Of course the LEDs have different needs that have to be treated in a separate circuit from the 12V power supply.
I will look further into motor controllers then.
>>997669
This. The PWM signal can come out from a microcontroller or from a jellybean astable oscillator (like the still popular 555 timer). You can control the duty cycle with a potentiometer in either case.
If the fan is 12 V DC but without PWM input, you can still use the PWM signal to drive a beefy enough transistor to switch on and off the fan.
>>997683
If all you want is a fan you can set the speed of, any four-pin PC fan and a FanMate is all you need.
>>997702
W-well controll it with an arduino then.
Quick question,
The fan in my laptop is making a noise like a car is idling at 3000 rpm.
I opened it up, got all the dust out and everything but the noise continued,
When i tap the fan it stops making a sound and keeps on spinning,
is this fan broken or is there another fix without buying a new fucking 40$ fan
>>997707
Sounds like the bearing is fucked and the fan is now off balance. There is no cheap and easy /diy/ fix for this.
Buying a new fan is likely the best option.
>>997733
>>997716
If you're replacing the fan, do the thermal pads and thermal paste at the same time. It's super-cheap, and will save you opening the laptop yet again.
And if there's only ~$10 difference, it's totally worth it getting a new heatpipe assembly as well, particularly if (as often happens) the later revisions of it were improved.
just go for any réhobus schematics
>>997633
>>997650
You can control PC fans with voltage. They are usually rated for 12v, but you can run them as low as 5v. It will just spin slower. Search in Google for: Low noise adapter fan, and you will see that it just uses a resistor. Some fans also have specified the lowest voltage they will run of: http://www.farnell.com/datasheets/1322331.pdf (Rated voltage: 12v, Operating voltage range: 5.0 to 13.8v)
That works for fans with 2 and 3 pin connectors. If you want PWM you need 4 pin connector.
>>997669
>Or you could get a four-wire fan, and control it with a voltage-driven PWM signal.
Yea but it's simpler to just get "any PC fan and control it with a DC motor controller"
>>997702
>Generally speaking: Does the transistor heat up like a resistor does?
>Because in that case a transistor would always be more energy efficient than a poti, right?
A resistor and a transistor both will heat up.
The "most efficient" way would be to get an 18v power supply and a DC-DC buck converter, to set the voltage that the fan gets. But you're spending a lot more money to save a very tiny amount of power.
A Zalman Fan Mate was just a power transistor that throttled the DC voltage, by the by. It didn't require a 4-wire motor, and didn't involve PWM at all (pic related).
>>997702
>Generally speaking: Does the transistor heat up like a resistor does?
Not even remotely as much if you do it well. If you use a bipolar NPN transistor, wite its collector to the negative end of the fan and its emitter to ground. Leave the possitive end of the fan connected to 12 V. Wire the output of your PWM source to the base of the transistor through a resistor; the resistor value must be chosen so that the current going through the base multiplied by the current gain of your transistor (beta or hfe as specified in the datasheet) is higher than the current the fan would consume when powered directly to 12 V. To calculate the current going to the base through a given resistor, assume PWM output high voltage on one side of the resistor, 1 V (perhaps an overestimation of the base voltage) on the other side, and apply Ohm's law. If you do it this way, your transistor will switch fully with a tiny voltage drop, so the dissipated power (voltage drop times current) will be negligible.
>>998171
(cont.)
For example, when PWM output high is 12 V, base voltage when on is 1 V, hfe is 40, and your fan consumes 200 mA at 12 V, you need a current of at least 200 mA / 40 = 5 mA to completely switch the transistor on, and thus a resistor of (12 V - 1 V) / (5 mA) = 2.2 kohm maximum to reach that base current.
>pic related
>>998181
Wouldn't that load need a freewheeling diode?
>>998171
>If you do it this way, your transistor will switch fully with a tiny voltage drop,
If you do that, the transistor is just barely conducting the required current. You need to overdrive it rather heavily to minimize the voltage drop in it. Datasheets typically specify 5-10 times higher base drive when talking about saturation voltages and such.
Simply, yes you can use resistors or connect diodes in series. A 1n4007 is cheap as fuck and will cause a voltage drop of about 0.7v per diode.
