Alarm. - Here is Circuit Schematic 3-Wire Cooling Fan Monitor. Cooling fan is an essential part in almost all power electronics systems. Here is a simple circuit for monitoring the instrument cooling fan activity to raise an audio-visual alert incase of the fan failure. This is a proven solution to prevent costly disasters caused by over temperature inside the power electronics instrument. This little adapter circuit can be used with any 3-Wire instrument cooling/exhaust/blower fan.
|Figure 1. Schematic 3-Wire Cooling Fan Monitor|
Prototype was tested with a 80mm/12VDC/3-Wire cooling fan, using a 5VDC lab power supply. Even at 5VDC, the fan performance is good, and the operation is very silent because of the low rpm rate. Besides, total power consumption is comparatively low!
You can use almost all standard 3-wire cooling fans with this adapter circuit. However, for optimum performance it may become necessary to slightly change the values of components C1, R4 and C2. Finally, note that the connector of a common 2-wire fan has a red and a black cable. The red cable goes to the positive of the power supply (Vcc) and the black to the negative (Gnd). However two fans with 3-wire connectors may not have the same wire colors.
The Original Article : "3-Wire Cooling Fan Monitor"