Published April 1, 2024 © GPL3+

IoT Rail Vibration Generator

With this device, rail vibration is generated for measuring the movement and transmitting the data for later analysis.

BeginnerWork in progress5 hours152

Things used in this project

Hardware components

Microchip AVR IoT Mini Cellular Board

WT901C-TTL 9-Axis vibration accelerometer

SparkFun Dual H-Bridge motor drivers L298

3.3V to 5V level converter

DC motor, 12 V

Breadboard (generic)

Jumper wires (generic)

Steel profile

Steel spring

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Drill / Driver, 20V

Story

Introduction

This project demonstrates how to build a hardware-based vibration device, for simulating the forces that are applied to curvature sections of rails in a suburban train line.

For simulating the forces exerted on the rail, two motors each with an eccentric piece placed on the rotor, are attached for creating vibration on each of the horizontal and vertical axes.

The device obtains the vibration data from an accelerometer and transmits to a web site for later analysis.

Motivation

The building of suburban train lines represent a challenge when they are developed in high density urban locations like Mexico City. Suburban train lines are very convenient for transporting many people; they are environmental friendly, tend to free roads of many cars and are a very good option for traveling among different living, working, touristic and commerce places in the city.

In Mexico City, we have underground, superficial and aerial (over columns) suburban train lines. In the aerial part of Line 12, there are train rails with high curvature sections, due to the complicated trace that runs among the streets, houses and buildings.

Vibration produced by the transit of trains over rails is a well-studied area. Nevertheless, it is interesting to develop a device for experimentation and self study of the phenomenon. Also, it could be convenient to send the vibration data over cellular networks, instead of WiFi, due to its inaccessibility along the train lines. Thus, it is a good idea to get experience with the AVR IoT Mini Cellular Board.

IoT Rail Vibration Generator

The device was built using recycled material for the main structure. The train rail is simulated using a section of steel profile obtained from a recycling warehouse. It is mounted over two conical steel springs, the longest diameter of the spring close to the rail, for better vibration. The rail and the springs are attached with long screws to an aluminum square plate.

Rail section attached to a conical spring over an aluminum plate.

The two dc motors are attached with a thin metal plate to the steel profile. One will apply a force in the vertical direction, and the second one in the horizontal direction. The vibration is obtained by an eccentric made in a 3D printer with an attached screw.

Motor attached to the rail with eccentric for creating vibration.

Integrating Each Module

Because this project is considered as a proof of concept and for learning purposes, fast prototyping DuPont jumpers were used for the connections between the AVR 128DB48 IoT board, the H-Bridge and the WT901C-TTL sensor.

Components connections using DuPont jumpers.

Each module was connected independently with the AVR128DB48 IoT board and tested with the corresponding code before integrating a complete device. In the following sections, we describe this.

WT901C Sensor

The WT901C 9-axis digital module incorporates a 3-axis accelerometer, 3-axis gyroscope, and 3-axis magnetic field sensors. It integrates a Kalman dynamic filtering algorithm for solving the current real-time motion posture of the module and has a 200Hz rate.

The WT901C sends data thru a UART, allowing for serial communication with the AVR 128DB48. The Serial2 port was used in this board. The transmitting line (TX) of the sensor is attached to the receiving line (RX) of the AVR 128DB48 board. Same for the RX line, attached to the TX line in the micro controller board (crossed connections).

AVR 128DB48 IoT board and the WT901C sensor connections.

A PC program was used for the first test of the WT901C sensor, together with a USB to serial TTL cable. This allowed to obtain the 9-axis data, display it and graph.

For fast prototyping and using the WT901C sensor, a Software Development Kit (SDK) is provided. This is quite useful, as it implements the interaction of the sensor with different micro-controllers, programming languages and applications.

The first program for testing the WT901C sensor and obtaining the data, employ the Serial2 instruction as we are using the USART2 on the AVR 128DB48 board. For some reason, this didn't work, so we had to turn to the software serial implementation.

SoftwareSerial used for communicating with the WT901C sensor.

Dual H-Bridge Motor Driver L298

The dual H-Bridge motor driver based on the L298 integrated circuit is very convenient for driving two DC motors with PWM signals. It incorporates two control lines for each motor, allowing for full stop or change of direction, according to the following table:

H-Bridge Motor Driver L298 control lines.

It is important to note that the AVR 128DB48 IoT is a 3.3V device and the H-Bridge motor driver expects input signals at 5V. For this reason, a pair of voltage shifters were used. The H-Bridge motor driver has a pair of jumpers that, when placed, send full voltage to the motors. When removed, PWM signals can be applied for adjusting the motors speeds. This bridge also incorporates a 5V regulator that was used for feeding the voltage shifters.

AVR 128DB48 IoT and the H-Bridge motor driver connections.

PWM signals are generated by using the analogWrite instruction. A test program was developed derived from the gpio.ino example, in which the switch 0 is detected via interrupts. In our case, we increase the duty cycle for the PWM signal with each press.

PWM signal is generated bu using the analogWrite instruction.

The complete code for both test programs can be found in the attachments to this project.

IoT Implementation

Further analysis of the vibration data will be done in Matlab. For this reason, we are programming the code for sending the vibration data to the ThingSpeak web site. AT-commands are being investigated for implementing this functionality with the AVR 128DB48 IoT board.

Code

/*
Test for the AVR 128DB48IoT and the WT901C TTL sensor.
Using sofware serial.

WT901CTTL      128DB48 IoT
    VCC <--->  3.3V
    TX  <--->  PF5 (RX2)
    RX  <--->  PF4 (TX2)
    GND <--->  GND

    21 de marzo de 2024
*/

#include <SoftwareSerial.h>
#include <REG.h>
#include <wit_c_sdk.h>

#define ACC_UPDATE		0x01
#define GYRO_UPDATE		0x02
#define ANGLE_UPDATE	0x04
#define MAG_UPDATE		0x08
#define READ_UPDATE		0x80
static volatile char s_cDataUpdate = 0, s_cCmd = 0xff; 

static void CmdProcess(void);
static void AutoScanSensor(void);
static void SensorUartSend(uint8_t *p_data, uint32_t uiSize);
static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum);
static void Delayms(uint16_t ucMs);
const uint32_t c_uiBaud[8] = {0,4800, 9600, 19200, 38400, 57600, 115200, 230400};

SoftwareSerial mySerial(PIN_PF5, PIN_PF4); // RX, TX

void setup() {
  Serial3.begin(115200);
  mySerial.begin(9600); // BaudRate
	WitInit(WIT_PROTOCOL_NORMAL, 0x50);
	WitSerialWriteRegister(SensorUartSend);
	WitRegisterCallBack(SensorDataUpdata);
  WitDelayMsRegister(Delayms);
	Serial3.print("\r\n** wit-motion normal example **\r\n");
	AutoScanSensor();
}

int i;
float fAcc[3], fGyro[3], fAngle[3];
void loop() {
    while (mySerial.available())
    {
      WitSerialDataIn(mySerial.read());
    }
    while (Serial3.available()) 
    {
      CopeCmdData(Serial3.read());
    }
		CmdProcess();
		if(s_cDataUpdate)
		{
			for(i = 0; i < 3; i++)
			{
				fAcc[i] = sReg[AX+i] / 32768.0f * 16.0f;
				fGyro[i] = sReg[GX+i] / 32768.0f * 2000.0f;
				fAngle[i] = sReg[Roll+i] / 32768.0f * 180.0f;
			}
			if(s_cDataUpdate & ACC_UPDATE)
			{
				Serial3.print("acc:");
				Serial3.print(fAcc[0], 3);
				Serial3.print(" ");
				Serial3.print(fAcc[1], 3);
				Serial3.print(" ");
				Serial3.print(fAcc[2], 3);
				Serial3.print("\r\n");
				s_cDataUpdate &= ~ACC_UPDATE;
			}
			if(s_cDataUpdate & GYRO_UPDATE)
			{
				Serial3.print("gyro:");
				Serial3.print(fGyro[0], 1);
				Serial3.print(" ");
				Serial3.print(fGyro[1], 1);
				Serial3.print(" ");
				Serial3.print(fGyro[2], 1);
				Serial3.print("\r\n");
				s_cDataUpdate &= ~GYRO_UPDATE;
			}
			if(s_cDataUpdate & ANGLE_UPDATE)
			{
				Serial3.print("angle:");
				Serial3.print(fAngle[0], 3);
				Serial3.print(" ");
				Serial3.print(fAngle[1], 3);
				Serial3.print(" ");
				Serial3.print(fAngle[2], 3);
				Serial3.print("\r\n");
				s_cDataUpdate &= ~ANGLE_UPDATE;
			}
			if(s_cDataUpdate & MAG_UPDATE)
			{
				Serial3.print("mag:");
				Serial3.print(sReg[HX]);
				Serial3.print(" ");
				Serial3.print(sReg[HY]);
				Serial3.print(" ");
				Serial3.print(sReg[HZ]);
				Serial3.print("\r\n");
				s_cDataUpdate &= ~MAG_UPDATE;
			}
      s_cDataUpdate = 0;
		}
}

void CopeCmdData(unsigned char ucData){
	static unsigned char s_ucData[50], s_ucRxCnt = 0;
	
	s_ucData[s_ucRxCnt++] = ucData;
	if(s_ucRxCnt<3)return;										//Less than three data returned
	if(s_ucRxCnt >= 50) s_ucRxCnt = 0;
	if(s_ucRxCnt >= 3)
	{
		if((s_ucData[1] == '\r') && (s_ucData[2] == '\n'))
		{
			s_cCmd = s_ucData[0];
			memset(s_ucData,0,50);
			s_ucRxCnt = 0;
		}
		else 
		{
			s_ucData[0] = s_ucData[1];
			s_ucData[1] = s_ucData[2];
			s_ucRxCnt = 2;
			
		}
	}
}

static void ShowHelp(void){
	Serial3.print("\r\n************************	 WIT_SDK_DEMO	************************");
	Serial3.print("\r\n************************          HELP           ************************\r\n");
	Serial3.print("UART SEND:a\\r\\n   Acceleration calibration.\r\n");
	Serial3.print("UART SEND:m\\r\\n   Magnetic field calibration,After calibration send:   e\\r\\n   to indicate the end\r\n");
	Serial3.print("UART SEND:U\\r\\n   Bandwidth increase.\r\n");
	Serial3.print("UART SEND:u\\r\\n   Bandwidth reduction.\r\n");
	Serial3.print("UART SEND:B\\r\\n   Baud rate increased to 115200.\r\n");
	Serial3.print("UART SEND:b\\r\\n   Baud rate reduction to 9600.\r\n");
	Serial3.print("UART SEND:R\\r\\n   The return rate increases to 10Hz.\r\n");
  Serial3.print("UART SEND:r\\r\\n   The return rate reduction to 1Hz.\r\n");
  Serial3.print("UART SEND:C\\r\\n   Basic return content: acceleration, angular velocity, angle, magnetic field.\r\n");
  Serial3.print("UART SEND:c\\r\\n   Return content: acceleration.\r\n");
  Serial3.print("UART SEND:h\\r\\n   help.\r\n");
	Serial3.print("******************************************************************************\r\n");
}

static void CmdProcess(void){
	switch(s_cCmd)
	{
		case 'a':	if(WitStartAccCali() != WIT_HAL_OK) Serial3.print("\r\nSet AccCali Error\r\n");
			break;
		case 'm':	if(WitStartMagCali() != WIT_HAL_OK) Serial3.print("\r\nSet MagCali Error\r\n");
			break;
		case 'e':	if(WitStopMagCali() != WIT_HAL_OK) Serial3.print("\r\nSet MagCali Error\r\n");
			break;
		case 'u':	if(WitSetBandwidth(BANDWIDTH_5HZ) != WIT_HAL_OK) Serial3.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'U':	if(WitSetBandwidth(BANDWIDTH_256HZ) != WIT_HAL_OK) Serial3.print("\r\nSet Bandwidth Error\r\n");
			break;
		case 'B':	if(WitSetUartBaud(WIT_BAUD_115200) != WIT_HAL_OK) Serial3.print("\r\nSet Baud Error\r\n");
              else 
              {
                mySerial.begin(c_uiBaud[WIT_BAUD_115200]);
                Serial3.print(" 115200 Baud rate modified successfully\r\n");
              }
			break;
		case 'b':	if(WitSetUartBaud(WIT_BAUD_9600) != WIT_HAL_OK) Serial3.print("\r\nSet Baud Error\r\n");
              else 
              {
                mySerial.begin(c_uiBaud[WIT_BAUD_9600]); 
                Serial3.print(" 9600 Baud rate modified successfully\r\n");
              }
			break;
		case 'r': if(WitSetOutputRate(RRATE_1HZ) != WIT_HAL_OK) Serial3.print("\r\nSet Baud Error\r\n");
			        else Serial3.print("\r\nSet Baud Success\r\n");
			break;
		case 'R':	if(WitSetOutputRate(RRATE_10HZ) != WIT_HAL_OK) Serial3.print("\r\nSet Baud Error\r\n");
              else Serial3.print("\r\nSet Baud Success\r\n");
			break;
    case 'C': if(WitSetContent(RSW_ACC|RSW_GYRO|RSW_ANGLE|RSW_MAG) != WIT_HAL_OK) Serial.print("\r\nSet RSW Error\r\n");
      break;
    case 'c': if(WitSetContent(RSW_ACC) != WIT_HAL_OK) Serial3.print("\r\nSet RSW Error\r\n");
      break;
		case 'h':	ShowHelp();
			break;
		default :break;
	}
	s_cCmd = 0xff;
}

static void SensorUartSend(uint8_t *p_data, uint32_t uiSize){
  mySerial.write(p_data, uiSize);
  mySerial.flush();
}

static void Delayms(uint16_t ucMs){
  delay(ucMs);
}

static void SensorDataUpdata(uint32_t uiReg, uint32_t uiRegNum){
	int i;
    for(i = 0; i < uiRegNum; i++)
    {
        switch(uiReg)
        {
            case AZ:
				s_cDataUpdate |= ACC_UPDATE;
            break;
            case GZ:
				s_cDataUpdate |= GYRO_UPDATE;
            break;
            case HZ:
				s_cDataUpdate |= MAG_UPDATE;
            break;
            case Yaw:
				s_cDataUpdate |= ANGLE_UPDATE;
            break;
            default:
				s_cDataUpdate |= READ_UPDATE;
			break;
        }
		uiReg++;
    }
}

static void AutoScanSensor(void){
	int i, iRetry;
	
	for(i = 0; i < sizeof(c_uiBaud)/sizeof(c_uiBaud[0]); i++)
	{
		mySerial.begin(c_uiBaud[i]);
    mySerial.flush();
		iRetry = 2;
		s_cDataUpdate = 0;
		do
		{
			WitReadReg(AX, 3);
			delay(200);
      while (mySerial.available())
      {
        WitSerialDataIn(mySerial.read());
      }
			if(s_cDataUpdate != 0)
			{
				Serial3.print(c_uiBaud[i]);
				Serial3.print(" baud find sensor\r\n\r\n");
				ShowHelp();
				return ;
			}
			iRetry--;
		}while(iRetry);		
	}
	Serial3.print("can not find sensor\r\n");
	Serial3.print("please check your connection\r\n");
}

/*
 * PWM test program for one motor. The duty cycle is increased with the switch 0.
 * 
 * March 31st, 2024
 */

#include <Arduino.h>

#define IN1 PIN_PD3   // A2
#define IN2 PIN_PD4   // A3
#define PWM1 PIN_PD5  // A4
#define IN3 PIN_PE2   // D5
#define IN4 PIN_PE1   // D6
#define PWM2 PIN_PD0  // D9

/**
 * @brief Note that it is important that variables modified in an interrupt are
 * volatile, so that the compiler don't optimize them away.
 */
static volatile bool button_pressed = false;

/**
 * @brief Gets called when the SW0 button is pressed.
 */
static void buttonInterrupt(void) { button_pressed = true; }

// setting PWM properties
int dutyCycle = 150;

void setup() {
  pinConfigure(IN1, PIN_DIR_OUTPUT);      // IN1
  pinConfigure(IN2, PIN_DIR_OUTPUT);      // IN2
  pinConfigure(PWM1, PIN_DIR_OUTPUT);      // PWM

  // Motor off
  digitalWrite(IN1, LOW); 
  digitalWrite(IN2, LOW);
    
  // In order to configure a pin as an input, for example the button SW0 at
  // PD2, we can do the following:
  pinConfigure(PIN_PD2, PIN_DIR_INPUT | PIN_PULLUP_ON);

  // Then we can e.g. attach an interrupt to the button when it is pressed (on
  // the falling edge). If we want to have an interrupt when the button is
  // released, we'd need to use the rising edge instead.
  //
  // We could also use digitalRead(PIN_PD2) in a loop in order to check the
  // value continuously
  attachInterrupt(PIN_PD2, buttonInterrupt, FALLING);

  // We start the Serial3, which is used to print messages. As one can also
  // see on the same page in the hardware user guide, the USART3 is used for
  // sending messages to the debugger, which again is connected to the
  // computer via USB. We thus have to be careful to use Serial3 and not
  // Serial for printing
  Serial3.begin(115200);
  Serial3.println("Press SW0 for increasing the duty cycle up to 250");
}

void loop(){
  // Motor ON
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  analogWrite(PWM1, dutyCycle);
  
  if (button_pressed)
  {
    Serial3.println(F("Button pressed"));
    dutyCycle = dutyCycle + 10;
    if (dutyCycle > 255)
      dutyCycle = 60;           // Lowest dutycycle that activates the motor
    button_pressed = false;
    Serial3.println(dutyCycle);
  }
}

Credits

Alejandro Butron

1 project • 1 follower

IoT Rail Vibration Generator

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Motivation

IoT Rail Vibration Generator

Integrating Each Module

WT901C Sensor

Dual H-Bridge Motor Driver L298

IoT Implementation

Schematics

AVR 128DB48 rail vibration sensing device

Code

Test program for sending the WT901 sensor data to the AVR 128DB48.

PWM test program for one motor

Credits

Alejandro Butron

Comments

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IoT Rail Vibration Generator

IoT Rail Vibration Generator

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Motivation

IoT Rail Vibration Generator

Integrating Each Module

WT901C Sensor

Dual H-Bridge Motor Driver L298

IoT Implementation

Schematics

AVR 128DB48 rail vibration sensing device

Code

Test program for sending the WT901 sensor data to the AVR 128DB48.

PWM test program for one motor

Credits

Alejandro Butron

Comments

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