simple ADC Interfacing
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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.
simple ADC Interfacing
- 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
- 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) {