Diagram SOlution

This radiator temperature indicator can be designed using electronic circuit diagram bellow .Temperature indicator consists of two special zener diode, D1 and D2, connected in series to ensure accuracy of 5.96 V Zener voltage at 25 ° C. As long as the radiator temperature not exceeding 50 ° C, thermal indicator will flash a green LED, one orange will be provided for temperatures of 50 ... 75 ° C and a red LED, for temperatures above 75 ° C.

Zener voltage will increase by 20 mV for each temperature increase of a degree Celsius temperature. Radiator temperature corresponding voltage level is compared with two reference voltages, IC1 and IC2 using. When the temperature reaches 50 ° C, IC2s output goes to logic state "1" so that T3 leads and following ignition with diode D4. At 75 ° C, IC1s output is in logic state "1" and, therefore, T2 and T3 will, so that D3 and D4 lights are off. Link