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Can the pi power a 12v computer fan?

I bought a 12v computer fan (there is a picture on it attached) and i was wondering how I could power it from the pi or just in general. Please help.

Better news.

I do not know what voltage the screen needs.

I think I have a match for the PSU

and apart from the claim of a 4000kv test
(Transmission voltage
The national grid in the UK runs on mainly 400kV AC system with an HVDC system, that runs on 400kV too, across the English Channel.)  which is hopefully 4KV flash test, rather than 10 times the rating of our pylon voltage.

My HP and Dell power supplies, rated at 18 volts-ish, both give remarkably reassuring output readings.  Meaning that they could be substituted by me if I had a Charles Bronson - Death Wish moment, so I could actually try and get 12 volts from one of them to run Relays fans etc etc.



Well I just measured mine, with an uncalibrated, DMM.

AC output is 39.0 volts.
DC output is 18.3 volts.

This is rather perplexing.  Suggesting HALF WAVE rectification.

Advantage of a half wave rectifier is only that its cheap, simple and easy to construct. It is cheap because of the low number of components involved. Simple because of the straight forwardness in circuit design. Apart from this, a half wave rectifier has more disadvantages than advantages!

The formula is something like... 0.45 x RMS

So if I have 39 volts AC RMS and apply 0.45 I get 17.55, not a million miles or volts from the suggestion of half wave rectification.

To achieve 12 volts you should look for FULL WAVE unsmoothed, which would give...
0.9 x 39 = 35.1 volts.  3 times what you wanted.

But as it is a wide input voltage, the above does not make sense, except the part about cheap.

So possibly the power board has a wide input voltage capability and smoothing etc onboard,  OR  my readings taken OFF load are not representative of the output under load.



I dont think you can directly connect a 12 volt fan to the Raspi I/O pins. Would probably need a transistor as a switch. I think there was a post on the official Pi forum on the details for this.

Please help me, please

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