Silent PC Accessories:
For individuals spending extended periods on computers. The advantages of a noiseless PC are undeniable. Numerous websites now offer computer accessories tailored to enhance the tranquility of your desktop experience. The primary culprit for PC noise often resides in the CPU fan. In many instances, it can be replaced by a sizable passive heat sink, facilitating more efficient heat dissipation. The orientation of heat sink fins is strategically designed to maximize airflow driven through the case by the power supply fan.
Optimizing Airflow in Modern PCs:
Intel’s ATX type PC form factor specifications recommend utilizing cooling air in this manner. However, achieving success with modern machines necessitates meticulous attention to several factors. Firstly, selecting a processor with minimal power consumption, particularly in idle mode, is crucial. Chips utilizing the cost-effective 45 nm technology are excellent starting points. Secondly, meticulous planning of air circulation within the case is vital. Ensuring efficient ducting of airflow from the PSU through the passive CPU heat sink is imperative. However, a drawback of this setup is that fan speed is solely regulated by the PSU’s temperature, not the processor’s.
Installing a Fan Speed Controller:
To resolve the noise issue, the solution lies in installing a new fan speed controller and incorporating a temperature sensor onto the CPU heat sink. This controller operates by sensing the air temperature in both the PSU and the processor heat sink, adjusting the fan speed based on the warmer reading. This method ensures optimal cooling. With this objective in mind, the author devised a versatile fan speed controller utilizing a small microcontroller, a few transistors, and two NTC thermistors. The key component, IC1, is an 8-pin 8-bit ATtiny13 microcontroller from Atmel, boasting more than sufficient 10-bit resolution analog inputs for the task. The circuit, although not overly complex, incorporates two thermistors connected between NTC1 and NTC2 of K3 and ground, forming two voltage divider networks alongside R1 and R2.
Temperature Sensing and Fan Speed Control:
Voltages generated at NTC1 and NTC2 are directly proportional to the measured temperatures and are sampled by the analog inputs ADC2 and ADC3 of the microcontroller. Based on the measured temperature values, the controller dynamically selects one of ten fan speed settings. The higher of the two temperature readings is always prioritized. The output from pin 6 generates a pulse modulated waveform, regulating fan speed. The output Darlington configuration of T1/T2 propels the fan using the PWM waveform, created by R6/C2. This low pass network effectively filters out the 15 Hz fundamental frequency of the PWM output signal, minimizing any potential PWM noise originating from the fan windings.