Published August 24, 2018 © LGPL

Trigonometric Height Measurement with 3D Magnetic Sensor

A device to measure the height of walls/buildings with high school trigonometry: sensing angle with a 3D magnetic sensor, dot laser & level.

BeginnerFull instructions provided4 hours1,260

Trigonometric Height Measurement with 3D Magnetic Sensor

Things used in this project

Hardware components

Infineon XMC2GO - industrial microcontroller kit

Sparkfun breadboard holder

Seeed Studio Dot Lase

e-Paper Eink display

Spirit Level

SparkFun Pushbutton switch 12mm

SparkFun Ultrasonic Sensor - HC-SR04

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Hot glue gun (generic)

Story

Step 1: Theory of Operation

Remember high school trigonometry ? Most, students don't know why do they need to learn such crazy stuffs ! But, if you are an engineer, programmer, scientist, astronaut, pilot, mathematician - you know the use is everywhere. This project is a practical example how trigonometry can be used for real purpose.

The project utilizes the formula : tan θ = opposite side/ adjacent side , In a right triangle.

Theory of operation

Using a typical HC-SR 04 ultrasonic sensor distance between the base of the wall and the device is measured (adjacent leg)

A dot Laser is attached to the 3D magnetic sensor, the laser beam is targeted on the top part of the wall/building (which forms the hypotenuse. As the laser is adjusted to shine on the top part of the wall, it forms an angle which is measured with the 3D magnetic sensor.

Wall height (opposite) is calculated with the above formula and shown on a epaper display.

Step 2: Building the Hardware

First the 3D sensor, rotary knob and XMC1100 mcu board is glued (super/hot) on a breaboard holder plastic base. A leveling piece is glued on the rotary knob to measure initial angle.

1 / 3

Next, HC SC04 ultrasonic sensor, a laser, a user switch and a e-ink display is placed on the board to make electrical interconnections like this :

System components interconnection in progress

Finally all the interconnection according to the schematic looks like this -

Connection

Step 3: Programming

To program the system in Arduino IDE, the 2GO kit's board support must be added. This is done by following these steps -

Install and run Arduino IDE 1.8.5

Go to File > Preferences > Additional Board Manager URLs and paste https://github.com/Infineon/Assets/releases/download/current/package_infineon_index.json

Adding 2GO kit support on Arduino IDE

Now go to Tools > Board Manager > type "xmc" in search box and download board support files

board support installation

Now, we need Library for TLE493D 3D magnetic sensor.

Go to: https://github.com/IRNAS/TLV493D-3D-Magnetic-Sensor-Arduino-Library

Download the zip library and add to IDE

adding associated libraries

Next, Install Segger Link for communication between kit and IDE from here:

https://www.segger.com/downloads/jlink/JLink_Windows_beta.exe

Then, go to tools and set

Board: XMC1100XMC2Go

Serial Output Selection: On-board

Port: Port 11 (select whichever new port appears after plugging kit into USB)

port setup and flashing code

Step 4: Measurements

The following video demonstrates the device application. Enjoy -

Height measurement with 3D magnetic sensor

Step 5: Conclusion

This device can be used in high school math classes in for practical experiments. Also can be used in survey for civil installations. Modified version can be used in astronomy and position sensing too.

Please note that, this system will start to produce significant measurement error if too small or too large ( above 80 degrees ) angle are measured. In other words, objects with few cm height or hundred meters height will cause instrumentation error due to ultrasonic distance resolution, 3D magnetic sensor angular resolution, design alignments mismatch. It is also important to put the device with 2-3 meter of the base of the target object. Since, HC SR-04 ultrasonic sensor can measure upto 4 meters with 1-2 cm accuracy. This is a prototype design, for more accuracy, proper alignment and use of higher resolution sensors are recommended.

Code

#include <SPI.h>
#include "epd1in54.h"
#include "epdif.h"
#include "epdpai#include <SPI.h>
#include "epd1in54.h"
#include "epdif.h"
#include "epdpaint.h"
#include <Tle493d_w2b6.h>
#include <RTC.h>
#include <DeviceControlXMC.h>
#include "epdpaint.h"


int TRIGpin = 14;
int ECHOpin = 8;
int SWCHpin = 13;


int COLORED  = 0; // White in Black
int UNCOLORED = 1;  // Black in White
int pos = 20;

XMCClass xmc2go;

// TLV493 variables //
float Xm = 0.0;
float Ym = 0.0;
float Zm = 0.0;
float angleD = 0.0; // angle in degree
float angleR = 0.0; // angle in radian
long adjacent = 0.0; // base to device distance + offset 5 cm
long offset =5.0;
float height = 0.0; // height of wall

/////////////////////

unsigned char image[8192];   // takes 8k RAM 
//////////////////////////////////////////////////
// width must be multiple of 8
Paint paint(image, 0, 0);     
Epd epd;                     
Tle493d_w2b6 Tle493dMagnetic3DSensor = Tle493d_w2b6();
//////////////////////////////////////////////////////

void setup() 
{

pinMode (TRIGpin,OUTPUT);
pinMode (ECHOpin,INPUT);
pinMode (SWCHpin,INPUT);

///// Init Full Display Update ///////////
  if (epd.Init(lut_full_update) != 0) 
  {return;}
/////////////////////////////////////////////
  
///// Init Partial Display Update ////////
  if (epd.Init(lut_partial_update) != 0) 
  {return;}
//////////////////////////////////////////
////////// Clears Up Full Disp ///////////
// bit set = white, bit reset = black
  epd.ClearFrameMemory(0xFF);   
  epd.DisplayFrame();
  epd.ClearFrameMemory(0xFF);   
  epd.DisplayFrame();
//////////////////////////////////////////

}



void loop() 
{
  /// Get Mag sensor running here ///
  Tle493dMagnetic3DSensor.begin();
  delay(50);
  Tle493dMagnetic3DSensor.enableTemp();
  delay(50);
  Tle493dMagnetic3DSensor.updateData();

    Xm = Tle493dMagnetic3DSensor.getX();
    Ym = Tle493dMagnetic3DSensor.getY();
    Zm = Tle493dMagnetic3DSensor.getZ();
 // angleD = 180+(57.3*Tle493dMagnetic3DSensor.getAzimuth());
 // offset for level
    angleD = (57.3*Tle493dMagnetic3DSensor.getAzimuth())-90; 
    angleR = abs(angleD/57.3);

    digitalWrite(TRIGpin,LOW);
    delayMicroseconds(5);
    digitalWrite(TRIGpin,HIGH);
    delayMicroseconds(10);
    digitalWrite(TRIGpin,LOW);
   
    long duration_cm = pulseIn(ECHOpin,HIGH);
    adjacent = offset+ (duration_cm/58);
    
    
   height = tan(angleR)*adjacent;
   //height = tan(angleR)*200; 
  char VAL[4];
  //  Data Optained From Mag ///// 


   SPI.begin();
   SPI.setClockDivider(SPI_CLOCK_DIV4);
   SPI.setBitOrder(MSBFIRST);
   SPI.setDataMode(SPI_MODE0);
  // Set Active Area on Disp with Orientation and Color //
  // more RAM allows more disp area to be used at once
   paint.SetWidth(200);
  paint.SetHeight(200);
  paint.SetRotate(ROTATE_270);
  paint.Clear(UNCOLORED);
  
  paint.DrawVerticalLine (110,120,50,COLORED);
  paint.DrawStringAt(120,140, "Height", &Font16, COLORED);
  paint.DrawHorizontalLine (30,170,80,COLORED);
  paint.DrawStringAt(40,180, "Adjacent", &Font16, COLORED);
  
  paint.DrawLine (30,170,110,120,COLORED);
  
  // itoa int to string conv
  
  paint.DrawStringAt(5,90, "Height", &Font20, COLORED);
  paint.DrawStringAt(130,90, itoa(height,VAL,10), &Font24, COLORED);
  
  paint.DrawStringAt(5,65, "Angle", &Font20, COLORED);
  paint.DrawStringAt(130,65, itoa(abs(angleD+180),VAL,10), &Font24, COLORED);

  paint.DrawStringAt(5,40, "Adjacent", &Font20, COLORED);
  paint.DrawStringAt(130,40, itoa(adjacent,VAL,10), &Font24, COLORED);

  
  paint.DrawStringAt(10,10, "Units in cm & deg", &Font16, COLORED);

////////////////////////////////////////////////////////////////////////////////
   epd.SetFrameMemory(paint.GetImage(), 0, 0, paint.GetWidth(), paint.GetHeight());
   epd.DisplayFrame();
////////////////////////////////////////////////////////////////////////////////

   delay(200);

} // loop ends here //