Don’t let the icy road catch you out!

There is nothing new about car ice alarms. The first appeared many years ago and the author has produced one or two of these designs. Usually, the “ice warning” is given by an l.e.d. (light-emitting diode) which operates at a temperature of, say, 2C. A small margin above the ice point (0C) is desirable to provide an early warning.

Many circuits have used a thermistor to sense the temperature of the air close to the road surface. This method is satisfactory but there are some potential problems. Also, a l.e.d. is not altogether satisfactory to use as the warning device. During daylight hours, it might not even be seen, while at night it tends to be distracting.

The present design overcomes the above problems. It uses a special temperature-sensing IC (integrated circuit) to determine the temperature. This requires no calibration because it provides an accurately known voltage output at a given temperature. Instead of a visual warning, the signal given here is audible. This is not provided as a continuous tone but takes the form of intermittent bleeps that will not be found unduly distracting.