ADC converter

: This circuit is for conversion of anolog input (any physical quantity such as temperature) to digital output in binary form (which can be read by computer) and further it can be converted to binary decimal format. Task2: Construct an ADC circuit to convert 2 bit digital input to anolog output Circuit diagram for the conversion is given in Figure 2. LM339 comparator and 74147 priority encoder are used in this circuit. Analog input from the DC power supply is compared with reference voltage using LM339 comparator chip and then given to 74LS147 priority encoder chip. Binary output obtained from 74LS147 further can be converted to BCD (Binary coded decimal) format using 7447 chip, which can displayed on common cathode 7-sement BCD display as decimal digit. Use three out of four comparators available in LM339. IC pin diagrams of LM339 and IC 74147 are given in following pages. Digital binary output can be obtained from D0, D1 and D2 or pin nos. 9,7 and 6 of IC 74147. Note that LM339 is a quad comparator integrated circuit. It has open collector, therefore requires pull up resistors as shown in Figure 2 at the output of comparator. Use pull up resistors of 3 kΩ. Always use 1 kΩ resistors in series with the LEDs while using LM339 chip. Supply voltage to LM339 can be up to 15 V. Set the reference voltage appropriately. Before connecting ADC circuit, understand the operation of LM339 by connecting one of the comparator and checking the output. Pin diagram of LM339 is given below. 74LS147 is 10 to 4 priority encoder. For this IC, Input is active low and output is active low. Pin diagram is given below. Unused input pins of 74147 should not be left open and they need to be connected to 5 V input supply.