Our project is a standalone temperature and fan monitoring and control unit for the PC. It uses the temperature readings to adjust fan speeds in order to regulate temperature and noise. The system is flexible in that it can be configured to be either completely autonomous, or set up to be configurable. It is also highly configurable in the setting up of the features and parameters. The entire unit is controlled by the 2 Atmel Mega32 MCUs - 1 for the main control unit and 1 for the RF remote control, with inputs to the ADC (for thermal sensors), port pins, RS232 serial connection and output to the LCD, port pins and RS232 serial connection. The RF remote control controls specific settings of the unit. The main unit is powered off a standard 4-pin PC Molex power connector while the remote control is powered off a 9V battery.


Computer devices have steadily increased in transistor count and clock speed as dictated by Moore's Law. Despite various attempts at reducing power consumption and dissipation, power budgets have increased steadily, and thermal output has also increased correspondingly. Over the past 2 decades, microchips have gone from requiring no cooling, to passive cooling with a heatsink only and subsequently to active cooling with a heatsink and fan. As thermal output continues to increase, exotic cooling techniques that require large and fast spinning fans will undoubtedly be required.

Figure 1. Comparison of fan noise vs fan speed for various fans

With such high spinning fans comes another problem of noise. There is typically a tradeoff between cooling performance and generated noise. PC enthusiasts often go to great lengths in order to achieve an acceptable balance. Traditional fan systems have dealt with this problem either with manually adjustable fan speeds by the user or automatically by the host CPU. The former requires user intervention, which is cumbersome and potentially unsafe, and the latter requires intervention by the host CPU, possibly slowing down the system and requiring system hardware and software support for temperature monitoring and control. Autonomous standalone units are available, but they are rare and very expensive. A DigiDoc 5+ 5.25" front panel unit with similar features can cost over $50. We designed and build a flexible, inexpensive, microcontroller controlled standalone PC temperature monitoring and control unit that can either be run autonomously or configured manually.