Coolercontrol

by Martin Clausen (mc AT rotgradpsi DOT de)

This is a little circuit to slow down fans to avoid noise.

You use your PC only for internet or as a typewriter? So slow down your cpu and reduce power dissipation. Now you can slow down the cpu cooler and avoid its nasty sound. But sometimes fans cause trouble, because they do not start always at low voltages. Therefor this circuit starts the fan with a few seconds of full voltage and then comes down to approx. seven volts.

Table of contents:

Principle of Operation
Parts
Download of Circuit

Principle of Operation

When power is applied to the circuit, the capacitor C3 is discharged. Therefor the transistor can not conduct. The LM 317 sees a huge resistance to ground and delivers a high voltage at its output. Then the capacitor begins to charge. When the voltage across it has reached 0.7V + 4.9V, the transistor starts to conduct and the LM 317 will reduce its output voltage.

Parts

Semiconductors:
1 LM 317
1 BC 547
1 ZF 4.7
Capacitors:
3 10µF
Resistors:
1 470
1 1.8k
1 100k
Mechanic:
1 pbc
1 some thin wire

Download of Circuit

coolcont.gif circuit V1.00

The part description in schematics is read as follows:
part type + value in exponential form + package description + subpart number in package
for example: C1040805,1 means Capacitor, 100nF, package SMD 0805, first subpart in package

Disclaimer: No warranty at all!
Copyright by Martin Clausen, Germany.
Contact the author: mc AT rotgradpsi DOT de
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