Tuesday, 05 November 2013 20:36

Sharp GP2Y0A21红外线测距传感器

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Sharp GP2Y0A21是一颗红外线测距传感器,易于使用,价钱廉宜,且低功耗。 规格如下:
  • 距离测量范围:10至80cm(4“到32”)
  • 工作电压:4.5V至5.5V
  • 输出类型:模拟电压
  • 平均功耗:35mA
  • 峰值功耗:约200mA
  • 允许的最大角度:> 40°
  • 更新频率/周期:25 Hz/40毫秒
 
 
Sharp GP2Y0A21是一颗非线性(nonlinear)测距传感器,且是非连续性(non-continuity)输出,当距离小于8厘米,传感器将不能正常工作。其测距特性如图所示。
Distance measuring characteristic
 
 
减少噪音
Sharp GP2Y0A21 传感器的输出很不稳定,容易被干扰,最简单的解决方法是将两颗电容并联(100nF的10-100μF)连接VCC和GND之间。 电容必须尽可能靠近电源,如图:
Soldering capacitors onto IR sensor
 
 
使用Arduino读取Sharp GP2Y0A21的传感值
GP2Y0A21传感器只有三个接脚,VCC、GND和模拟输出(Analog output)。只要将其输出连接至微控制器的模拟输入(Analog input),就能读取传感器读取的值了。这里使用了一个Arduino读取Sharp GP2Y0A21的传感值。
Connecting Sharp GP2Y0A21 sensor to Arduino
 
  1. /*
  2.   Read values from Sharp GP2Y0A21 distance sensor and output to serial
  3.  
  4.   Sharp Distance Sensor GP2Y0A21 (10-80cm)
  5.   3.1V at 10cm to 0.3V at 80cm
  6. */
  7.  
  8. int ir_sensor = A0;
  9.  
  10. void setup() {
  11. //initialize serial communications at 9600 bps
  12. Serial.begin(9600);
  13. }
  14.  
  15. void loop() {
  16. int sensor_value = analogRead(ir_sensor); //read the sensor value
  17. Serial.println(sensor_value); //print the sensor vlue
  18. delay(500); //delay 500ms (0.5 second)
  19. }
 
上面提到Sharp GP2Y0A21 传感器的输出很不稳定,在相同情况下读取传感器,你不可能取得全部相同的值,因此必须多次读取传感器,然后取得其平均数。
  1. int ir_sensor = A0;
  2.  
  3. void setup() {
  4. Serial.begin(9600);
  5. }
  6.  
  7. void loop() {
  8. Serial.println(value_average(10)); //loop 10 times and get its average
  9. delay(500);
  10. }
  11.  
  12. int value_average(int average_count) {
  13. int sum = 0;
  14. for (int i=0; i<average_count; i++) {
  15. int sensor_value = analogRead(ir_sensor);
  16. sum = sum + sensor_value;
  17. }
  18. return(sum/average_count);
  19. } Code
 
Arduino有6个模拟输入,标记为A0到A5,每个模拟输入提供10位的分辨率(即1024个不同的值)。 5V为默认值, 因此读取5V将是1023,2.5V为512,依此类推。以下代码应用了Map函数把传感值转换成电压voltage
  1. int ir_sensor = A0;
  2.  
  3. void setup() {
  4. //initialize serial communications at 9600 bps
  5. Serial.begin(9600);
  6. }
  7.  
  8. void loop() {
  9. int sensor_value = analogRead(ir_sensor); //read the sensor value
  10. //convert to voltage ranged from 0V to 5V
  11. int voltage = map(sensor_value, 0, 1023, 0, 5); //0V=0, 2.5V=512, 5V=1023
  12. Serial.println(voltage); //print the sensor vlue
  13. delay(500); //delay 500ms (0.5 second)
  14. }
上面的例子只能显示四组不同的值(电压),即0V,1V,2V,3V。实际情况,你应该Map更大的值,比如 map(sensor_value,0,1023,0,255)
 
 
将传感值转换成厘米(cm)
以下方程式是根据Sharp GP2Y0A21 传感器的特性而取得的方程式
Equation
  1. int ir_sensor = A0;
  2.  
  3. void setup() {
  4. //initialize serial communications at 9600 bps
  5. Serial.begin(9600);
  6. }
  7.  
  8. void loop() {
  9. int sensor_value = analogRead(ir_sensor); //read the sensor value
  10. int distance_cm = pow(3027.4/sensor_value, 1.2134); //convert readings to distance(cm)
  11. Serial.println(distance_cm); //print the sensor value
  12. delay(500); //delay 500ms (0.5 second)
  13. } Code

以下代码读取100次的传感值,然后取得其平均电压
  1. int ir_sensor = A0;
  2.  
  3. void setup() {
  4. //initialize serial communications at 9600 bps
  5. Serial.begin(9600);
  6. }
  7.  
  8. void loop() {
  9. int distance = average_value(100); //loop 100 times and get its average
  10. Serial.println(distance); //print the sensor value
  11. delay(500); //delay 500ms (0.5 second)
  12. }
  13. int average_value(int average_count) {
  14. int sum = 0;
  15. for (int i=0; i<average_count; i++) {
  16. int sensor_value = analogRead(ir_sensor); //read the sensor value
  17. int distance_cm = pow(3027.4/sensor_value, 1.2134); //convert readings to distance(cm)
  18. sum = sum + distance_cm;
  19. }
  20. return(sum/average_count);
  21. }
Read 18540 times Last modified on Tuesday, 05 November 2013 20:59

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