Airflow monitor protects components

Many electronic components,

including fourth-generation UPs, require forced-air cooling. However, the reliability of electromechanical components, such as cooling fans, lags behind that of electronic devices. Even if a fan does not fail, blockage of the air-intake vents can reduce airflow. The circuit in Fig 1 helps you protect against high-temperature-induced system failures by monitoring the performance of the cooling system.

The circuit combines a temperature transducer with a heater resistor. R1 is a surface-mount resistor that sits underneath the DIP-packaged transducer, IC1. The heat from R1 conducts through the IC and the pc board. The rise in IC1's temperature depends on the airflow across the package and tracks the temperature increase in adjacent high-power ICs.

If cooling efficiency decreases, IC1's temperature rises. IC1 includes two user-programmable setpoint alarms, which you can use to warn of impending system failure. For example, the lower setpoint limit can reduce the µP's clock speed or shut off unnecessary peripherals while the upper limit initiates a controlled system shutdown. Alternatively, the lower limit can activate auxiliary power while the upper limit controls the clock.

Authored by Wes Freeman at EDN,