This circuit uses IC LM 35 to sense the temperature. output of LM 35 is given to the IC ADC 0804 (IC4) which converts the analog output of the LM 35 to digital output. The ADC 0804 is a 8 bit ADC .Eight LED’s are connected to the output of ADC to show the output logic.If needed the LED’s can be avoided and the output can be connected to any suitable external circuit like temperature controller etc.A 5V fixed voltage regulator based on 7805 (IC1) powers the circuit.Another variable voltage regulator based on LM317(IC2) is used to provide the reference voltage to the ADC 0804.
Notes:
- POT R10 can be used to adjust the scale factor of the ADC. The reference voltage at pin 7 of ADC0804 should be 2.5 V for full scale.
- IC1: 7805, IC2: LM317, IC3: LM35, IC4 ADC0804
- D1 TO D8: DIODE LED, R2 TO R8: 1K 1/2 WATT RESISTOR
Spesifikasi IC LM35
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full -55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35's low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a -55° to +150°C temperature range, while the LM35C is rated for a -40° to +110°C range (-10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.
Feature IC LM35
•Calibrated directly in ° Celsius (Centigrade)
•Linear + 10.0 mV/°C scale factor
•0.5°C accuracy guaranteeable (at +25°C)
•Rated for full -55° to +150°C range
•Suitable for remote applications
•Low cost due to wafer-level trimming
•Operates from 4 to 30 volts
•Less than 60 µA current drain
•Low self-heating, 0.08°C in still air
•Nonlinearity only ±¼°C typical
•Low impedance output, 0.1 Ohm for 1 mA load
