Power and potentiate multiple fans

[Norcasc]

Hey guys,

It´s been a while since i´ve been to my last electronic class, so i hope you guys can help me out with this

I´d like to power a row of 10 CPU fans to enhance the efficiency of the ancient radiators (to heat) of my ground floor.

I planned to use 10 fans (80mmx80mm, 12V, 0,17A), powered by a 12V charger. I´d like to control the speed of all fans by a potentiometre.

I would have simply set all fans in parallel, so all of them will turn with the same speed (*cough* i hope thats right ^^)

I would have chosen the charger based on my rusty school electrotech knowledge...

My problem is to find the right potentiometre.

This is what i planned to order:
https://www.mindfactory.de/product_...x25mm-2400-U-min-24-dB-A--schwarz_746495.html

https://www.amazon.de/Leicke-Netzte...6PUNMu4-icbEeoxE-nUtR0gU6ksPO9V_kggXS-1B_iVOQ

I attached a pic with a circuit in case my description was confusing ^^...

My questions are:
Is it right to use the parallel circuit here...
What potentiometre do i need to control the speed of the fans (best one with commonly used values)
Is the powersupply suitable for this purpose... (If not what values do i need)
I already use some old fans powered by old phone chargers and it makes the room down significantly warmer, just in case you doubt all of this makes any sense :-D

Thanks in advance

 

[duke37]

A resistor will need to disipate a lot of heat so reducing the advantage of the fans.

Parallel conection is good but series connection is also possible. 10 fans in series will need 120V which could perhaps be obtained from the mains with a bridge rectifier, depending on your supply. A lamp dimmer could control the fan speed. Connection to the mains will need excellent insulation installation.

I would stick to 12V and use a switch or swiches to select various numbers of fans. If you use two banks of five fans, the you could use all 10 or only 5, or all 10 with the two banks in series for half speed.

 

[Norcasc]

Thx for the quick answer

Parallel conection is good but series connection is also possible. 10 fans in series will need 120V which could perhaps be obtained from the mains with a bridge rectifier, depending on your supply.
This is to high for me and i don´t wanna play with a 120V source ^^... hence I´d stick to a parallel circuit...

So the 12V charger in the link would do the job and power all 10 fans in parallel?
If yes what potentiometre would you recommend (what values)? [Link for an example would be great ]
And would the circuit work as i drew it?

 

[Bluejets]

Forget the potentiometer, too high a power requirement.
At a minimum, 20W and cost with availability will be impossible.

Not sure the basic cpu fans lend themselves to speed control though.
There are 3 wire units which do but you need the controller. Then you have 10.

Best suggestion with what you have is with Duke37's idea of simply letting a number of fans operate at any given time and switch in more or less depending on the airflow requirement.

I very much doubt though that even 10 cpu fans will have a noticeable effect at circulating air in a room.
A 1 x desk fan would probably do much better.

 

[duke37]

I see that you need to enhance the output of a radiator. A small amount of air blown over the surface, perhaps ducted, will have a considerable effect
Each fan takes a miserly 0.17A so ten will take less rhan 2A. The charger you show can provide 5A so will have an easy time.

 

[Bluejets]

Perhaps a ceiling mounted fan to get the heat back down out of the rafters would be a consideration.

 

[Harald Kapp]

10 fans in series will need 120V which could perhaps be obtained from the mains with a bridge rectifier

I strongly recommend not to go this way. Dealing with mains is dangerous if you do not know exactly what you do.

There are 3 wire units which do but you need the controller. Then you have 10.

All 10 fans could be controlled by the same controller.

Any 12 V fan without control input (2 wire fan) can be controlled using pwm. Suitable controllers are available online, e.g. this one (really just an example).

A 1 x desk fan would probably do much better.

That may be an option in terms of noise reduction. 10 PC fans will generate a lot of noise. A large single fan at low speed (I think you do not need fast airflow across the radiator, just a smooth steady flow) will be much more quiet.

 

[dave9]

I like the desk fan idea, but a typical brushless, 2 wire computer fan is easily controlled by voltage or current limiting, as long as you stay above a minimum value as they need more torque to spin up than to keep spinning.

If I went with computer fans I would use fewer, larger diameter, and thicker too if you can find some that are cost effective. I am doubtful that you really need speed control because fans come in a variety of RPMs to choose from. Choose a modest RPM, say 1200 or lower to keep the noise level reasonable, and wire them in parallel.

Even then I would as soon get something like the following, not have to bother with wiring it up or buying a separate PSU, and note that it has 3 speed settings. While the fastest would be more effective airflow than 10x of the fans you linked, the medium or low speed might be ideal for lower noise. This fan design will create a vortex that pushes heat further into the room than a row of thin 80mm computer fans would, even if they had the same total airflow rate.

https://www.amazon.com/dp/B001R1RXUG/

 

[Bluejets]

So why not simply bring the heat back down out of the rafters..??

BTW I have one of the fans you link to and they are as noisy as.....