Chapter 7 ADC and Sensor Programming 1 Microcontroller

Chapter 7 ADC and Sensor Programming 1

Microcontroller Connection to Sensor via ADC 2

An 8 -bit ADC Block Diagram 3

Resolution versus Step Size for ADC (Vref = 5 V) n-bit 8 10 12 16 Number of steps 256 Step size 5 V /256 = 19. 53 m. V 1024 5 V /1024 = 4. 88 m. V 4096 5 V /4096 = 1. 2 m. V 65, 536 5 V /65, 536 = 0. 076 m. V Note: Vref = 5 V 4

Vref Relation to Vin Range for an 8 -bit ADC Vref (V) 5. 00 4. 00 3. 00 2. 56 2. 00 1. 28 1. 00 Vin in Range (V) Step Size (m. V) 0 to 5 5 / 256 = 19. 53 0 to 4 4 / 256 = 15. 62 0 to 3 3 / 256 = 11. 71 0 to 2. 56 / 256 = 10 0 to 2 2 / 256 = 7. 81 0 to 1. 28 / 256 = 5 0 to 1 1 / 256 = 3. 90 Note: In an 8 -bit ADC, step size is Vref/256 5

Vref Relation to Vin Range for an 10 -bit ADC Vref (V) 5. 00 4. 96 3. 00 2. 56 2. 00 1. 28 1. 024 Vin. Range (V) Step Size (m. V) 0 to 5 5 / 1024 = 4. 88 0 to 4. 096 / 1024 = 4 0 to 3 3 / 1024 = 2. 93 0 to 2. 56 / 1024 = 2. 5 0 to 2 2 / 1024 = 2 0 to 1. 28 / 1024 = 1. 25 0 to 1. 024 / 1024 = 1 Note: In a 10 -bit ADC, step size is Vref/1024 6

A Simultaneous 2 -bit ADC 7

ADC 0848 Parallel ADC Block Diagram 8

MAX 1112 Serial ADC Block Diagram 9

Successive Approximation ADC 10

Potentiometer Connection in Edu. Pad 11

Thermistor Resistance vs. Temperature ('C) 0 25 50 75 100 Tf (K ohms) 29. 490 10. 000 3. 893 1. 700 0. 817 12

Thermistor (Copied from http: //www. maximintegrated. com) 13

Thermistor (Copied from http: //www. maximintegrated. com) 14

LM 34 and LM 35 15

Getting Data to the CPU 16

LM 45 Connection in Edu. Pad 17