Car temperature indicator circuit


Posted on Aug 15, 2012

The circuit is used to indicate two different water temperature trip points by turning on LEDs when the temperatures are reached. The circuit is constructed around the LM2904 dual operational amplifier powered from the 12 V auto system. The thermistor is in series with a 10 kSi resistor from ground to the positive 9.1 V point. The top of the thermistor is tied to both non-inverting inputs of the LM2904. The voltage at these inputs will change as the thermistor resistance changes with temperature.


Car temperature indicator circuit
Click here to download the full size of the above Circuit.

Each inverting input on the LM2904 has a reference, or threshold trip point, set by a 10 kfi resistor and a 2 kfl potentiometer in series across the 9.1 V regulated voltage. When this threshold is exceeded on the non-inverting input of LM2904, the TIL220 LED lights. The two trip points can be recalibrated or set to trip at different temperatures by adjusting the 2 k? potentiometer in each section. In addition to being used as warning lights as shown here, circuits can be added to turn on the fan motor or activate a relay.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

12v LED Light
Adc
Time-Out Circuit
Arduino Digital audio player
10 w amplifier using tda2003
ems metaboard
S1L9251X Cd-rom 48x Rf Amp Semiconductor
TDA9813T TDA9813T VIF-PLL With QSS-IF And Dual FM-PLL Demodulator
Headlamp dimmer controlled foglamps FORD RAPTOR
Reading and writing Atmega168 EEPROM Tutorial
Combination of common-source grounded emitter amplifier
OP27 multiple S-type thermocouple circuit



Top