Problem about Direct curre%nt Fan? So I have an active sub woofer with a heat si

Question

Problem about Direct curre%nt Fan? So I have an active sub woofer with a heat sink at its back panel. I want to install a DC fan on it (the one that is used on computers), and u%se the internal transformer as the fan's power source. The transformer delivers 12volts and 17volts to the main amplifier unit. I've tapped the fan to the 12volt terminals of the transformer, and it worked at normal %RPM. But it gets very hot after few minutes and it smells. The transformer can supply 12 volts DC at 2 amps and the fan is rated at 12 volts, 0.12 amps. So my question is what kind of resistor should I use to make% the fan work without overheating? I tried to put a 4ohm resistor in s%eries (it's color blue, but idk h%ow much watts it was rated) but it still runs hot, but cooler than bef%ore. The resistor gets kinda hot too. Should I use other semiconductors? If so, can you give me a diagram or instructions? thanks in advance.

Explanation / Answer

Transformers supply AC only, they do not work on DC. So you are driving the fan with AC, and it will not work at all.

No resistor, just supply 12 volts DC to the fan and it will operate fine.

edit: but perhaps you mean a DC supply, not a transformer. In that case the fan should operate fine. 12 volts DC is 12 volts DC. The currents do not matter as long as the supply can supply more current than the fan needs. The supply could be rated at 500 amps and it would still be fine.

I suspect you have a defective fan. Did you check the 12 volts with a meter? See if it is actually 12 volts DC? Try using a 12 volt battery?

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