Posted on Tuesday, April 19, 2011 • Category: Sensors
With this simple circuit you will be able to control the speed of a DC fan according to temperature measured by a temp sensor. Itís an ideal add-on for your PC cooling fans to eliminate produced noise. Requested by some correspondents, this simple design allows an accurate speed control of 12V dc fan motors, proportional to temperature.
A n.t.c. Thermistor (R1) is used as temperature sensor, driving two directly coupled complementary transistors wired in a dc feedback circuit.
An optional circuitry was added to remotely monitor fan operation and to allow some sort of rough speed indication by means of the increasing brightness of a LED.
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