>Just a couple points on this..
>1)      BC556 is a PNP TO-92 transistor. The above circuit requires an=
 NPN.

        I gotta sleep, BC546 :o)

>2)      The BC556 is only good for 100mA Ic, not 1-2A

        Yep, right.

>3)      With 1K we'll be getting no more than 4.3mA base current, that=
 means
>        the transistor wouldn't (even typically) be saturated (even if was
>       good for 1-2A. I like to see Ic/Ib ~=3D 20 for BJTs in hard=
 saturation,
>        so you need 100mA of base current, requires another transistor
>        (though the BC556 is too wimpy even for this). Maybe a 2SC8550
>        TO-92 PNP BJT driving a TIP31 through a 43R 1W resistor.=
 (dissipates
>        about 1/2W with fan on).  Then your 1K base resistor would be ok.

        Wasn't a couple? :o) Yes, the transistor was (badly) calculated from my=
 mind. I think I gotta have some sleep :o(

>4)      I agree with the need for a diode across the fan.

        Ufa! At least one :o)

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