The document differentiates between analog and digital signals, explaining that analog signals vary continuously while digital signals consist of discrete values. It highlights the importance of Analog-to-Digital Converters (ADCs) in translating analog signals into digital format for processing, and discusses different types of ADCs, their advantages, disadvantages, and key parameters to consider in selecting an appropriate ADC. Additionally, it provides example applications of ADCs and includes sample code for implementing ADC in programming.

1. ADC

3. WHAT IS ANALOG AND DIGITAL
SIGNAL?
ANALOG SIGNAL:-
A quantity that varies continuously with time is
known as a Analog signal.
DIGITAL SIGNAL:-
It is a signal that represents a sequence of discrete
values. In other words it has only two values
LOGIC ‘0’ OR LOGIC ‘1’

4. Examples of analog signals:
 Thermometer – mercury height rises as temperature
rises
 Car Speedometer – Needle moves farther right as
you accelerate
 Stereo – Volume increases as you turn the knob.
Examples of digital signals:
 Light switch can be either on or off
 Door to a room is either open or closed

5. Most of the signal that we want to process are analog
i.e.: they are continuous and can take inifinite no. of values
x(t)
t
Analog Signal
IMPORTANCE OF ADC
 Physical quantities to be measured are in analog form
 Microcontroller understands only digital values

6. Digital systems require discrete digital data
ADC converts an analog information into a
digital information
Digital System?Analog Digital
Why ADC ?

7. Examples of A/D Applications
 Microphones - take your voice varying pressure waves in the air
and convert them into varying electrical signals
 Strain Gauges - determines the amount of strain (change in
dimensions) when a stress is applied
 Thermocouple – temperature measuring device converts thermal
energy to electric energy
 Voltmeters
 Digital Multimeters

8. CHOOSING A PERFECT ADC
Parameters to be considered while choosing a ADC
 SPEED
 RESOLUTION
 ACCURACY
 STABILITY

9. t
Ts
Q
xq(t)
Accuracy
t
Ts
xq(t) Higher Sampling rate
t
Q
xq(t)
Higher Resolution

10. Accuracy of A/D Conversion
There are two ways to best improve accuracy of A/D
conversion:
 increasing the resolution which improves the
accuracy in measuring the amplitude of the analog
signal.
 increasing the sampling rate which increases the
maximum frequency that can be measured.

11. Types of ADCs
•Flash ADC
•Sigma-delta ADC
•Dual slope converter
•Successive approximation converter
•Parallel Comparator ADC

12. ADC Resolution Comparison
0 5 10 15 20 25
Sigma-Delta
Successive Approx
Flash
Dual Slope
Resolution (Bits)
Type Speed (relative) Cost (relative)
Dual Slope Slow Med
Flash Very Fast High
Successive Appox Medium – Fast Low
Sigma-Delta Slow Low
ADC Types Comparison

13. SUCCESSIVE APPROXIMATION ADC

14. Successive Approximation ADC
 A Successive Approximation Register (SAR) is added to
the circuit
 Instead of counting up in binary sequence, this
register counts by trying all values of bits starting with
the MSB and finishing at the LSB.
 The register monitors the comparators output to see if
the binary count is greater or less than the analog
signal input and adjusts the bits accordingly

15.  Sets MSB
 Converts MSB to
analog using DAC
 Compares guess to
input
 Set bit
 Test next bit
SAR DAC
Out
VIN
-
+
Successive Approximation
1000 0000
Is Vin > ½ ADC range?
0100 0000
If no, then test next bit

16. Successive Approximation
Advantages
 Capable of high speed and
reliable
 Medium accuracy compared
to other ADC types
 Good tradeoff between speed
and cost
 Capable of outputting the
binary number in serial (one
bit at a time) format.
Disadvantages
 Higher resolution successive
approximation ADC’s will be
slower
 Speed limited to ~5Msps

18. INSTRUCTIONS FOR ADC
 Init_Adc();
 Int Analog_Read(A0);

19. PROGRAM
#define F_CPU 16000000
#include <avr/io.h>
#include "Ilabslib_16.h"
#include <util/delay.h>//COM14
int main(void)
{
Lcd_Init();
Lcd_Clrscr();
Lcd_Goto(2,1);
Init_Adc();
while(1)
{
int value1= Analog_Read(A0);
Lcd_Clrscr();
Lcd_Write_Int(value1);
_delay_ms(200);
}
}

20. #define F_CPU 16000000
#include <avr/io.h>
#include "Ilabslib_16.h"
#include <util/delay.h>//COM14
int main(void)
{
Lcd_Init();
Lcd_Clrscr();
Lcd_Goto(2,1);
Init_Adc();
while(1)
{

21. {
int value1= Analog_Read(A0);
Lcd_Clrscr();
Lcd_Write_Int(value1);
_delay_ms(200);
Serial_Write_Int(value1);
Serial_Write_String("t");
}
}