Digital Anemometer

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Digital Anemometer

  1. 1. IISTDIGITAL ANEMOMETER Kosuru Sai Malleswar Harmeet Singh Rajil Ramesh A.An instrument that can measure both the speed and the direction of the wind flow
  2. 2. Introduction An anemometer is a device for measuring wind speed. Coupled with a weather vane whichindicates the direction of the wind, it forms a complete setup for describing the wind at any givengeographical location. There are a variety of anemometers available currently which are classified on the basis oftheir operating principle. Cup anemometers, Windmill anemometers, Hot-wire anemometers, LaserDoppler anemometers, Sonic anemometers, Ping-pong ball anemometer and Acoustic ResonanceAnemometers are a few to name. Two-dimensional (wind speed and wind direction) anemometersare used in applications such as weather stations, ship navigation, wind turbines, aviation andweather buoys.Our Design The anemometer that we have made as a part of this event is of cup type. It consists of fourhemispherical cups each mounted on one end of four horizontal arms, which in turn were mountedat equal angles to each other on a vertical shaft. On an anemometer with four cups it is easy to seethat since the cups are arranged symmetrically on the end of the arms, the wind always has thehollow of one cup presented to it and is blowing on the back of the cup on the opposite end of thecross. Due to the shape of the cups, more pressure and hence more force is exerted on the concavesurface of the cups as compared to the convex surface resulting in an unbalanced torque causingthe shaft to rotate. The air flow past the cups in any horizontal direction rotated the shaft in amanner that was proportional to the wind speed. We have used a DC motor in place of a dynamoto convert the shaft rotation to equivalent voltage. For measuring the angle of wind, we have used a wind wane. The design of a wind vane issuch that the center of gravity is directly over the pivotal axis, so that the pointer can move freelyon its axis, but the surface area is unequally divided. The side with the larger surface area is blownaway from the turdle, so that the smaller side, with the pointer, is pivoted to face into the winddirection. Most wind vanes have directional markers beneath the arrow, aligned with thegeographic directions. In the present design, we have used a simple single turn resistivepotentiometer attached to the wind wane as our sensor. The voltage at wiper point is clearlyproportional to the angle of the rotating dial.Once we have the sensors in place, we can calibrate them to obtain the true wind speed anddirection. By giving the analog voltage outputs of these sensors to a microcontroller after somesignal conditioning, we can convert them to digital format for displaying on LCD.
  3. 3. Block Diagram Figure 1: Block diagram of anemometer and wind direction measurement setupSignal Processing unit The voltage produced by the motor in generator mode is proportional to the velocity of therotating shaft which is proportional to the wind speed. So we made a plot of wind speed versus thevoltage produced. From the graph, we found the offset and the gain. According to these results,we programmed ATMEGA128 Microcontroller to read the voltage through 10 bit Analog toDigital Converter (ADC) units, perform scaling operations and display the speed value on 2X16LCD Module. The supply voltage to the Microcontroller is 5V. The voltage corresponding to the angle is indicated by the wiper arm of potentiometer. Thisis read by another ADC channel of Microcontroller and scaled to obtain the angle and display onLCD. Figure 2: Signal Conditioning unit
  4. 4. Conclusion Anemometer which can measure wind speeds from 2 m/s to 22 m/s with an accuracy of0.05 m/s along with the set up for measuring the wind direction based on the reference directionwith a resolution of 0.3516 degree has been made. This system was connected withMicrocontroller unit to display the speed and the angle on LCD.Code for measuring speed and angle and displaying on LCD#include <avr/io.h>#define F_CPU 14.7456e6#include <avr/interrupt.h>#include <util/delay.h>#include "lcd.h"#define adc_delay 40#define samples 5uint16_t adc_reading;float c,fr;float speed,angle;uint8_t count=0;uint16_t adc_read(unsigned char Ch){ uint16_t res; Ch = Ch & 0x07; ADMUX= 0x00| Ch; ADCSRA = ADCSRA | 0x40;
  5. 5. while((ADCSRA&0x10)==0); res = (uint16_t)ADCL; res|= (((uint16_t)ADCH)<<8); ADCSRA = ADCSRA|0x10; return res;}void lcd_print_float(uint8_t row, uint8_t col,float value){ float fract; lcd_print(row,col,(int)value,3); lcd_cursor(row,col+3);lcd_wr_char(.); fract=(int)(1000*(value-(int)value)); lcd_print(row,col+4,fract,3);}//Main Functionint main(void){ DDRC = DDRC | 0xF7; PORTC = PORTC & 0x80; ADCSRA = 0x00; ADMUX = 0x00; ACSR = 0x80; ADCSRA = 0x86;
  6. 6. lcd_set_4bit();lcd_init(); lcd_string(" SPEED | ANGLE "); lcd_cursor(2,8);lcd_wr_char(|); while(1) { adc_reading=adc_read(0); c=(float)adc_reading; c=c*5000/1024; if(c>70) { speed=c*0.0093; speed+=3.0846; } else { speed=0.000; } lcd_print_float(2,1,speed); _delay_ms(100); adc_reading=0; for(count=0;count<5;count++) { adc_reading+=adc_read(2); _delay_ms(100); } angle=(float)adc_reading; angle/=5; angle=angle*360/1024; lcd_print_float(2,9,angle); }}

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