Variable Fan Controller

When the fan seized up in my source and I changed it to a type with much less noise, turned on my computer, the largest source of noise CPU cooler fan. The computer I have a boxed Pentium III processor in slot 1, which is practically dismountable and fan replacement would be difficult. `Boxing` is a type of fan with ball bearings and replacement of the type of plain bearing to reduce noise, while cooling, but not reliability. Another option was to reduce the fan speed. I tried the program Speedfan. This enabled to set the fan speed, but I was unable to convince him to regulate the speed according to CPU temperature.
Variable Fan Controller - schematic

Variable Fan Controller - img1

The PSU I have the controller in [1] , which I witnessed in earlier computers. I wanted to use it for the CPU fan, I used to but your friend "discovered" the regulator is used in battery charger for model. Involvement of the regulator in Figure 1 is ingeniously simple. The whole controller has only three components: sensors - NTC Thermistor, Trimmer for temperature control and MOSFET. The transistor is the best "standard" type with a threshold voltage around 4 V. For use in PC controller had to be adjusted. It should be that the fan is grounded, otherwise it does not capture special fan outlet "rotation". For proper function of the controller under quite simply figure A transistor to produce the opposite type of conductivity and change the polarity and the fan. The resulting involvement of the figure 2 is not accompanied by a protection circuit. The thermistor is connected to the controller a short cable. The frequent handling inside the PC could happen that turn leads somewhere. The regulator according to Figure 1 , the fan has stopped rotating, which could have fatal consequences especially for AMD. The regulator according to Figure 2 , in which case the current flow stops and the thermistor trimmer, transistor T2 is closed and the transistor T3 is connected in parallel to T1, opens. The fan is powered by the almost full supply voltage. The opening of T2 requires very little current, the transistor is open and current,...

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