Good morning. I'm looking just to add a variable external potentiometer to a 120>12v power supply output to control this blower fan. Is a pot all I need for variable voltage/speed output? And if so, is it just any 12v rated pot?
Thank you much!

 

Welcome to AAC!
Can you post a link to the particular power supply?

 

@Alec_t Thanks for the welcome!

Here's a couple pics of the PSU. So is it basically putting a pot in line with hot? Or is there more to it?

Thanks for replying.

 

Here's a couple pics of the PSU. So is it basically putting a pot in line with hot? Or is there more to it?

There's more to it then that, unless the fan takes very little current (which is not likely).
How much current does the fan require?

Generally a PWM circuit works best for that purpose.

 

@crutschow heres the details.

 

The fan rating is 2.5A and your power supply is 1.75A, so Houston, you have a problem.

 

@crutschow Didn't catch that. However, checking the blower fan on the power supply, gives tons of air output....

Am I missing something?

 

Yes, you are missing the fact that your power supply would probably suffer an early death if operated that way.

I second using a PWM controller. A 3A 12V capable one is lss than 10 bucks on Amazon or Ebay.

Bob

 

Yes, you are missing the fact that your power supply would probably suffer an early death if operated that way.

I second using a PWM controller. A 3A 12V capable one is lss than 10 bucks on Amazon or Ebay.

Bob

Ahh silly me! Beings this is such a massive electronics site - anyone know of a good place for a used PS?
Thanks again!

 

Time expired to edit....

@BobTPH @crutschow or @Alec_t

Can you tell me if this power unit would work for the fan? This one says its 12v / 5a

https://www.amazon.com/Supply-LEDMO-Adapter-100-240V-Transformers/dp/B06Y64QLBM/

Thank you!

 

Barely and not for long. Do you run your car engine at MAX RPM nonstop? I'd look for a minimum of 7A and preferably 10A but then I'm conservative.

 

Might want to add a little more care in your wiring there as well. Crimping the ends in some eyelets would be ideal but at the least you may want to cut away those hanging strands...

 

A 5A supply should be fine. I have never sized my supply to 3 times the required current.

Bob

 

Barely and not for long. Do you run your car engine at MAX RPM nonstop? I'd look for a minimum of 7A and preferably 10A but then I'm conservative.

My plan was using the PWM controller and running the blower at %20-%50, definitely not %100, for maybe 15 minutes at a time, off and on. So do you think that PS would work in that manor?

@narkeleptk Yes, this was just to kick the fan on and see how much air it blows. Everything will be soldered up and heat shrunk when done.

@BobTPH - just saw your post. So knowing what I wrote above, 5A seems alright?

 

12V → 555 Pwm → N Mosfet → Fan

CMOS type 555, N Mosfet Ids ≥ 10A, Vds ≥ 20V

Some N, P type MOSFET Components Simple Data.

 

My plan was using the PWM controller and running the blower at %20-%50, definitely not %100

In that case the power supply you have may be sufficient.
A fan's motor current drops off rapidly with speed, since the fan load is non-linear, i.e. 50% fan speed requires less than 50% power.

 

The start-up current of a DC motor is several times the rated normal running current (2.5A) , so a 5A-rated SMPS type supply as per the post #10 link might object to the start-up (bearing in mind that '5A' is in units of 'Internet Amps', which may be exaggerated). Your existing 12V supply, on the other hand, looks to be the old school chunky transformer type, which generally can tolerate a brief current surge. I agree with Crutschow.

 

@ScottWang @BobTPH @Alec_t and @crutschow ok I think we're square on the PS now, TY very much.

On the PWM controller, does this look applicable on changing % fan speed? :12V 10A
https://www.amazon.com/HiLetgo-12V-40V-Controller-Switch-Module/dp/B00QVONO20/

 

On the PWM controller, does this look applicable on changing % fan speed? :12V 10A

Yes, I would expect that to work for you.
It has a more than sufficient current and voltage rating.

Let us know how it works.

 

Thank you very much Crutschow