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Topic: Powering and controlling groups of fans (12V DC) (Read 3 times) previous topic - next topic

Delque

I want to automatically control groups of fans' speed, the idea is that the power for the fans is supplied by a PC power supply and the power for the arduino from the USB. There will be multiple groups and each group will generally consist of 8 fans, not higher.

Fan chart: http://catalog.nidec-servo.com/digital/english/general/pdf/D1225C.pdf (The 2150 RPM 12V version)

The fan specification:
- Starting current: 530mA
- Current: 123mA
- Voltage range: 5.0-13.2V

A group of fans (8):
- Starting current: (about) 4.3A
- Current: (about) 1A
- Voltage range: 5-12V

I have seen an example (http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/) with a L293D chip but from what I have read it can't handle the current needed to power 8 fans, at least not the starting current.

A normal PC fan controller (http://www.lamptron.com/products/view/Fan_Controller_FC5V2)regulates the voltage output by turning a knob. What I want is to do the same except without the manual need to turn the knob but instead automatically controlled by the arduino depending on inputs on the computer.

The end product will be build to fit in a 5.25" bay so the components have a space limitation.

So my question is: How would I power and control a group of fans? What components do I need?

Delque

Quote from: KE7GKP

You did not mention reversing the fan direction, so it is not clear why you would need an H-bridge (like L293).

I certainly don't need nor want a reverse fan direction. It was an example I found which seemingly did what I seek, I'm pretty new to this so I'm not very familiar with what methods is needed for what applications. I just read up on what a H-bridge is and it is certainly not exactly what I need.

Quote from: KE7GKP

A simple power NPN transistor would seem all that is necessary to control the group of fans. 



Quote from: KE7GKP

it is not necessarily the case that the Lamptron (and similar) controllers use voltage to vary the speed of the fans. It is more common to use PWM to control the speed of DC motors. Except for the case of fan motors which have a speed control input. But the fan you specified does not appear to have this option.

The Lamptron fan controller states:
- DC Input: +12v (Standard 4-Pin Connector)
- DC Output: 0-12v

So I am sure it does work by regulating the voltage, but I may be incorrect? But if they use PWM instead how do they control fans that does not have PWM support? The fan I specified works on the Lamptron fan controller.

True, the fan does not have PWM support standard.

Quote from: KE7GKP

You seem to already have the "how would I power" question answered. You said that they will be powered from a PC supply. OK

Ahh formulated wrongly, it was meant more for the wiring on the component (if different from the L293D).

Quote from: KE7GKP

The question "how I control the group of fans" seems almost as simple. Use a single power NPN transistor to switch the current to the fans. Either simple on/off, or using PWM to control speed (same circuit either way).

Can you guide/recommend one that can handle the load I started in the first post?

Grumpy_Mike

Quote
But if they use PWM instead how do they control fans that does not have PWM support?

No all motors will respond to PWM, do you understand it?:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

For motor control see:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html

Delque

Quote from: Grumpy_Mike

Quote
But if they use PWM instead how do they control fans that does not have PWM support?

No all motors will respond to PWM, do you understand it?:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

If they don't regulate voltage then how do they control it as in what kind of component?

I do know how PWM works. The fan does not have natively support for PWM (the fourth pin for control input) so to use PWM would require a component and would that be better then voltage regulation?

I have only seen the fan been controlled by fan controller (like the Lamptron Fan Controller FC5V2) that regulates the voltage, at least that is what I assume since, like the Lamptron, there is not one word about PWM in the specifications and they take a 3pin connector for the fans, where as a PWM fan has a 4pin connector.

Grumpy_Mike

Quote
I do know how PWM works. The fan does not have natively support for PWM (the fourth pin for control input) so to use PWM would require a component and would that be better then voltage regulation?


Then if you think that you don't know how PWM works, please read the link I posted.
PWM needs no support either third or fourth pin on a fan.

Delque


This is the typical circuit used to control a load like a fan or a solenoid from an Aduino pin:



That circuit will work just as well for multiple fans as for one fan.
That circuit will also work for PWM control of fan speed.


Thanks. This seems to be exactly what I need and the TIP120 can handle 5A is just what I need. Is the diode strong enough for the required load I need?


Then if you think that you don't know how PWM works, please read the link I posted.
PWM needs no support either third or fourth pin on a fan.

I did not mean that the fans wont work with PWM. I meant they don't have an internal control that takes a PWM signal to control the speed of the fan.

Groove

Quote
the TIP120 can handle 5A is just what I need

If it is "just" what you need, then you may actually need something a little meatier, to handle peaks and variations.
Per Arduino ad Astra

Delque


Quote
the TIP120 can handle 5A is just what I need

If it is "just" what you need, then you may actually need something a little meatier, to handle peaks and variations.

It isn't "just" like that. A group of 8 fans have a starting current of 4.3A but only a current of 1A after they have started, so it seems this is really all I need. Just because I'm curious what else do you have in mind? :)

Delque


It is not good practice to use a parts at their maximum ratings for steady-state conditions. 
A peak startup current of 4A for a 5A rated transistor is fine.

Extactly, with only 1A current under full load after startup it should be quite stable using the TIP120.

AndrewStone

http://www.toastedcircuits.com Lightuino LED driver: 16 sources, 70 sinks, remote controlled.  Also high powered LED drivers.

eaycrcr

Can I just run what I'm thinking by you guys?

The output voltage of an NPN Transistor, wired as above, will vary with a PWM input? So said Transistor could be used to VARIABLE speed, SINGLE direction control of a 12V DC Motor?

If so, very exciting for me!  :D

Grumpy_Mike

Quote
So said Transistor could be used to VARIABLE speed,

Why did you not read the links I posted at the start of this thread. If you had then all these questions would have been answered.
If you did not understand the links then why did you not ask about what you didn't understand.

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