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Motherboard fan header boost circuit

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Hallo to all ,

I was wondering if anyone have built a circuit that allows you to add more than one fans on a single fan header , exceeding the permittable motherboard capacity . I can understand that this may be built with transistors or mosfets wired in series with the fan header  , but how exactly?

As you said, adding more than 1 fan may exceed the mb/s capacity. Moreover, any functionality that this header would have-such as to measure the RPM- will not work. So, why don't you add the fan directly to the PSU 12v? You can add as much as you want there.

The idea is to control the fans according to system temps , not  only to power them. I believe using the motherbord header is the only way to do it. As for the tacho signal , I will connect only one fan rpm wire to the header , as the fans will all be the same.

o i see. one more question: you have 4 wire fans or 3 wire fans?

Three wire fans . I have tried in the past with 4wire fans and  managed to control 3 fans with a LM358 based circuit , but never with 3wire.


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