Electronics > Projects, Designs, and Technical Stuff

Limiting start up current of a 12V PC fan

(1/7) > >>

paul_g_787:
Hi.

I have a little project I am working on which turns on a fan using a transistor.

The fan is rated at 12V 160mA  which actually draws about 120mA in the real world once running.

My power supply is an old router power supply I found which provides max 200mA at 11.8V. My circuit uses 11mA without the fan so this is perfect!

However when the fan starts up it can draw anywhere between 180mA to 305mA!
Using my bench supply I have confirmed that the fan starts fine every time with anything about 28mA.

So my question is what would be a simple way to limit the inrush current to the fan as to not overload the power supply? A resistor in series maybe to cap it at a max of say 180mA ish?  :-//

bdunham7:
My first question would be what happens when you simply let it start up with the overload?  Does the power supply have any issues with that?

wraper:

--- Quote from: paul_g_787 on April 09, 2022, 05:35:04 pm ---My power supply is an old router power supply I found which provides max 200mA at 11.8V.

--- End quote ---
Is it rated for 200mA or goes into protection at such current? 200 mA sounds low for a router.

paul_g_787:

--- Quote from: bdunham7 on April 09, 2022, 05:41:21 pm ---My first question would be what happens when you simply let it start up with the overload?  Does the power supply have any issues with that?

--- End quote ---

Nothing happens. It just works fine but draws this much more thand rated current for a fraction of a second.


--- Quote from: wraper on April 09, 2022, 05:43:09 pm ---
--- Quote from: paul_g_787 on April 09, 2022, 05:35:04 pm ---My power supply is an old router power supply I found which provides max 200mA at 11.8V.

--- End quote ---
Is it rated for 200mA or goes into protection at such current? 200 mA sounds low for a router.

--- End quote ---

It is rated for 200mA yes.

I was planning to connect a F200mA fuse to the power supply so was mainly worried about it blowing the fuse possibly.  :-//

wraper:
Then do not bother. Also 300mA is not enough to blow a 200mA fuse in a short time.

Navigation

[0] Message Index

[#] Next page