Stand alone Delta 4 pin PWM fan's direct from 12v supply?

[foxtrot_12]

Looking for the easist, most cost effective way to manually control 2 x 4 pin PWM delta fan's direct from 12v supply? They are going to be used in a diy evaporative air con I am putting together. They draw 3.9 amps each. Any advice much appreciated.

 

[Vic 40]

You can look for a fan controller which will be fed by the psu.

 

[Paperdoc]

I assume you do NOT plan to have this system as part of a computer case, but as a stand-alone cooling system (for a room?). So you won't have a computer PSU to use. But you still could use a fan controller module intended for use in a computer. The critical point, however, is power rating. At 3.9 amps each, those two fans consume about 20 TIMES the current of typical computer case ventilation fans. So you MUST review the output current specs for any fan controller you consider. As you do so, look at specs carefully for both controller and fans. Starting current on a fan motor is often 2 or 3 times the running current, although it only lasts for a couple of seconds. So, is that 3.9 amps spec for the fans a running current, or a peak starting current? Take that into account as you examine the specs of the controllers you consider.

Now, as to power supply, you don't need a computer PSU, you just need a sturdy 12 VDC supply capable of putting out up to about 10 amps continuous, 15 to 20 amps peak. Electronics shop, maybe even an automotive battery charger. The controller module's input connector (designed likely with a male 4-pin Molex connector to mate with a computer PSU output) will have two wires: a Red one for +12 VDC on one end, and a Black one for Ground next to it. Wire your power supply accordingly.

 

[foxtrot_12]

Thanks for the replies,

Your right I am making a cooler to cool a tent my family is just about to start a trip around Aus. I have a decent power supply 500 watts of solar and 450 amp battery bank @ 12v. I am just not sure what needs to go in between the supply and pwm fan. Can i use something like this?

http://m.gearbest.com/development-boards/pp_140613.html?currency=AUD&gclid=CMOyv6ykyMkCFQGAvQodrhsJdQ

I am thinking no because there is no Control wire to the fan leading me to think it's for a non pwm fan/motor? From the little understanding i have, the pwm is done enternally with in a pwm fan. So it will need supply wires, plus a signal wire to tell the pwm what to do. Any suggestions of specific controllers that i can hook directly to 12v supply?

Thanks

 

[Paperdoc]

First of all, why are you planning on using a PWM fan? Do you need to control its speed? Unless you do, a plain DC 12V fan will do your job. I would bet Delta has such units, too.

Secondly, you are correct about that controller. It is for use with a standard DC fan, or perhaps a DC fan that is designed to work properly with a pulsing DC supply that may contain spikes. It is the type of controller very commonly used for DC motor speed control via PWM techniques. What it does is send to the "standard" DC fan a PWM-modulated DC supply to achieve speed control. That particular controller does not appear to be suited to heavy current loads, and I note it says it is for use with stepper motors, so I expect it is NOT for standard DC motors.

The newer design of fans for inside computer cases called "PWM fans" are special-purpose units that include the final stages of a PWM controller inside the fan. For this fan design, the supplies to the fan must be a constant +12 VDC and Ground (on Pins 2 and 1) and a PWM signal at low power on Pin #4. Inside the fan its own circuit board components use the 12 VDC supply for the board's power AND to power the fan, so it must stay at 12 V. The board includes a controller chip that does the job of modulating the 12VDC supply by the PWM signal, and sends that to the motor for speed control. The makers of these fans specifically caution that feeding such a special-purpose fan with a DC supply that is already PWM modulated likely will damage the circuit board components causing the fan to fail.

If you want your fans to run at full speed all the time, a PWM motor CAN do the job - just wire its inputs for the +12 VDC and Ground, and nothing else. In the absence of a PWM signal for Pin #4, the fan will run full speed. But that motor may be more expensive than a plain 12 VDC motor without any PWM function.

If you want to control the motor's speeds, you MIGHT save money by using a plain 12VDC motor and adding a VOLTAGE controller (rather than a PWM controller). Just be aware that a motor controlled in this manner needs almost full voltage to start, and then you can slow it down. And it will stall if its voltage falls below some minimum. Of course, the controller would have to be able to handle the currents your motors use.

The other option might be to use a PWM controller with the current capacity you need and a DC motor designed for that use. I do not think the particular controller you linked to is the right one. I'm sorry I cannot recommend any particular items for this.