Fan Failure Detector circuit

  
The cooling is not only a PC using a small fan with an electronic commutator [1]. A special feature of these fans is that their removal is less dependent on the load. Indicators monitoring the DC component of current may therefore be very reliable. Interesting connection indicator I found in Electronic Design magazine [2]. The indicator in Figure 1, the only change in passing current. Measured current waveform is the fan in Figure 2 The voltage at the base of the transistor is filtered by resistor R1 and capacitor C1. The immediate changes in the supply current (during the fall) opens the transistor and discharges the capacitor C2.
Fan Failure Detector circuit - schematic

Fan Failure Detector circuit - img1

Fan Failure Detector circuit - img2

If he stops the fan, the voltage on the base and emitter of the same transistor and remains closed. Capacitor C2 is charged and logical level H output indicates a fault. Initial involvement was not accompanied MAX6501 circuit for indicating overheating. Serial sensing resistor for the fan normal PC too little resistance. For most fans meet resistance 12 ohm. Some fans, however, show only a small ripple current, see Figure 3 In this case, the resistor further increase. The cooling is not only a PC using a small fan with an electronic commutator [1]. A special feature of these fans is that their removal is less dependent on the load. Indicators monitoring the DC component of current may therefore be very reliable. Interesting connection indicator I found in Electronic Design magazine [2]. The indicator in Figure 1, the only change in passing current. Measured current waveform is the fan in Figure 2 The voltage at the base of the transistor is filtered by resistor R1 and capacitor C1. The immediate changes in the supply current (during the fall) opens the transistor and discharges the capacitor C2. If he stops the fan, the voltage on the base and emitter of the same transistor and remains closed. Capacitor C2 is charged and logical level H output indicates a fault. Initial involvement was not accompanied MAX6501 circuit for indicating overheating. Serial sensing resistor for the fan normal PC too little resistance. For most...



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