frost warning device - with a memory

frost warning device elektor december 1983 with a memory While Britain is normally spared the worst extremes of weather, there are times when it does not seem like that. This is particularly so in winter when the cold seems to be able to creep through any number of layers of woolen clothing. It"s unpleasant, but we just have to grumble and bear it. It would be very convenient, however, if you knew before stepping outside whether it is merely "cold" or "very very cold". If you have a thermometer the problem is solved, except, of course, that it has to be left outside - which sort of defeats the purpose. What is really needed is a temperature sensor mounted outside giving an indication inside. For motorists the problem is somewhat dif- The circuit diagram for this frost warner is shown in figure 1. The temperature is sensed by the LM 335Z which gives a specific value (A) in mV proportional to the measured temperature. This provides one of the inputs to comparator Al. The second inpu...