[small object velocimeter] only principle, no code

Project source ：Arduino ESP8266 Electromagnetic gun velocimeter &OLED Monitor

There are several problems in this project .

I don't know why the author quoted Adafruit_ssd1306syp This library .

• Not in the Arduino This library is found in the management Library .
• stay GitHub It seems that this library was found on , But it didn't say ：ssd1306syp
• The introduction of this library locally led to byte is ambiguous error
• take Adafruit_ssd1306syp Change library to Adafruit_ssd1306 There is no error after the Library .

so , This project was not reproduced successfully according to the author's code , Don't do too much code analysis here .

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principle

  Have you ever played smart car ？ There is a speed measurement module ！ It's that thing . I found a picture of the speed measurement module ( Here's the picture )

When there is no object in the groove to block the light , The receiving pipe is connected ,G14\G13 Low level detected . When objects block the light , The receiving pipe is not conductive . here , I hope the single chip microcomputer can read the high level . so G14\G13 It should be set to Pull up input . Under this logic , Only when there is no light blocking object detected as low level , It is detected as high level when there is a light blocking object . That such , Transparent objects are not easy to detect .

How to judge the speed ? Because the object passes through two photoelectric switches in turn , Then there will be time delay . The speed can be obtained by the distance between the two photoelectric switches .

Set the distance between two photoelectric switches ( Center to center distance ) by L , The delay time is T , So speed V = L÷T .

because ESP32 for Arduino There is a function that can read subtle units of time ：micros() . The relative time of two photoelectric switches can be recorded to calculate the speed .

To calculate more accurately , It is best to use interrupt function , And it should be set to trigger on the rising edge ！

Because there are objects blocking G14/G13 The port will detect a high level , The instantaneous recording from low level to high level is more accurate .

It is also very simple to calculate the kinetic energy of an object , Just input the mass of the object . It's used anyway ESP8266 , Direct web input .

Kinetic energy ： E = m×V×V×0.5

Then there is the specified specific kinetic energy 1.8 Joules per square centimeter ！ Just divide the area ~

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Code

Write a pseudo code to operate , Just write the calculation time 、 The speed part

ICACHE_RAM_ATTR void G13_InterFunction()    // Interrupt function 
{ 
  G13time = micros();            
  G13flag = 1;    
}


ICACHE_RAM_ATTR void G14_InterFunction()
{ 
  G14time = micros();            
  G14flag = 1;
}


void setup()
{
  attachInterrupt(G13, G13_InterFunction, RISING);     //  Rising edge trigger 
  attachInterrupt(G14, G14_InterFunction, RISING);     //  Rising edge trigger 
}

void loop()
{
  if(G13flag == 1 && G14flag == 1)
  {
    if(G13time>G14time)
      time = G13time - G14time;
    else
      time = G14time - G13time;
    G13flag = 0;
    G14flag = 0;
  }
} 

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summary

According to the original author ESP8266 It's still frustrating to hear that the project code of version has not been reproduced ！ But changing the code can be done .

I don't know what's wrong for the time being , See later ！

Project information

Let's release the code later , Make sure why there is a problem .

Ah ah ah ！ It's so sad to encounter setbacks ！！！