heat sink monitor

In almost any equipment in which a reasonable amount of energy is con- sumed, there is bound to be at least one heat sink that enables power semiconductors to get rid of their excess heat. The rating of a heat sink is normally determined on the basis of the maximum allowable temperature of the silicon chip: a rather haphazard method. The heat sink monitor described here constantly monitors the temperature of the heat sink. When that tempera- ture stays below 50...60°C, the green LED lights; between those tempera- tures and 70...80°C, the yellow (orange) LED lights; and above 70...80°C, the red LED lights. There is also the possibility of providing a relay with which, for instance, the load can be disconnected. The circuit is, in essence, a window comparator, in which sensor D1pro- vides a control voltage that rises 10 mV per degree Celsius. If the sensor voltage is lower than the voltage at the wipers of P1and P2, the outputs of opamps Al and A2 are low, and D2 lights. When the...