Battery Use Alloy Steel Room Temperature Indicator, Display Type : Analogue, Digital

Room Temperature Indicator is a very simple temperature monitor circuit used to guess the nature of temperature. The ten LEDs are used to indicate whether it is hot, cold, or lukewarm. Room Temperature Indicator uses a linear voltage display IC1, which drives a display of ten LEDs in a bar or dot mode. Diode D1 in reverse bias mode is used as a temperature sensor.
About the Circuit :

• The drive voltage for IC1 is derived from a potential divider consisting of a sensor R1 and preset P1. This combination is adjusted to set the required operating temperature, so that first LED D1 glows. As the temperature rises further, LEDs glows sequentially.
• IC1 is a linear voltage display IC consists of 11 comparators which gets sequentially triggered as the temperature rises. Accordingly, LEDs D1 to D10 glows. This is in dot mode. The display can be shown in bar mode also by connecting pin9 to pin3 by switching S2. But it should remembered that in dot mode, the total current will remain below 20mA, but in bar mode it may be 100mA when all LEDs light.