URM37 V3.2 Ultrasonic Sensor (SKU:SEN0001)

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Introduction

URM37 V3.2 Ultrasonic Sensor Manual - Rev 2.2

URM37 V3.2 Ultrasonic Sensor uses an industrial level AVR processor as the main processing unit. It comes with a temperature correction which is very unique in its class.

Specification

  • Power: +5V
  • Current: <20mA
  • Working temperature: -10℃~+70℃
  • Detecting range: 4cm-5m
  • Resolution: 1cm
  • Interface: RS232 (TTL), PWM
  • Servo control: One servo control output
  • Operating Mode: Serial; (PWM) passive control mode; Autonomous Mode; On/OFF Mode
  • Temperature sensor: 12 bits reading from serial port
  • Size: 22mm × 51 mm
  • Weight: 30g




Figure 1: URM37 V3.2 Beam Width
Figure 2: URM37 V3.2 Pin Definition

1. +VCC - +5V Power
2. GND - Ground
3. RST - Reset
4. PWM - PWM Output 0-25000US,Every 50US represent 1cm
5. MOTO - Servo control signal output
6. COMP/TRIG

COMP - On/OFF mode, when the detecting distance is smaller than a pre-set value, this pin pulls low.
TRIG - PWM or RS232 trigger pin

7. NC
8. RXD - RS232,TTL communication
9. TXD - RS232,TTL communication

Compare with other ultrasonic sensor

Compare with SRF08 and XL-MaxSonar-WRC1 Ultrasonic Distance Sensor Evaluating

Hardware requierments

  1. 1×URM37 V3.2 Ultrasonic Sensor
  2. 1×Arduino Microcontroller
  3. 1×IO Expansion Shield For Arduino(V5)
  4. 1×USB cable

Tools used

  • 4×jumper wire

Software

  • Arduino IDE

Working Mode Selection

The working mode can be changed by writing 0x00, 0x01 or 0x02 to EEPROM through serial port.

Mode 1: Serial passive control mode

Under this mode, the sensor is always waiting for command from serial port. Every time it receives a command, it will return the distance and wait for the next command. The degree in the command will be used to control a servo motor to rotate corresponding degree. Please note that this mode is always on. It can not be switch on or off.

Jumper setting for RS232 and TTL output

The selection of RS232 or TTL output level is switched by changing three jumpers (J1, J2, J3). A diagram below illustrates the setting:

RS232 Mode
TTL Mode



















Warning: Do not connect to TTL MCU when the output mode is set to RS232, doing so will permanently damage the unit.

This feature is only available for Rev2 and after. If there are no jumpers on the back of the sensor, the sensor is Rev1 and hence not supporting this feature.

TTL Mode Connection Diagram



RS232 Mode Connection Diagram



Module test

After you have connected the module according to the diagram,you can use our "URMV3.2HelpMate" to test the module online

URMV3.2HelpMate

The usage of the software is very simple: ensure that there is no other software on the computer takes up the serial port, and then running mate, select the COM Port, and choose the parameter what you want to measure,and choose the "Continuous Reading ".Click "Measure" it will measure the temperature and the distance.

Mode 2: Autonomous trigger mode

Under this mode, the sensor will make a sensor reading every 25ms and compare the reading with a threshold (pre-set, user is able to define this value by writing EEPROM), if the reading is equal or smaller than the threshold, pin COMP/TRIG will have low output. In the meantime, pin PWM will output the distance reading, every 50us low level stands for 1cm, by counting the number of these pulses, the distance can be calculated. This mode can be simply used as an ON/OFF switch.

First you need to write the desired distance threshold into the sensor module. Using the serial port and the following code.

The way to write its EEPROM can be found in the code below. And the distance is stored in address 0x00 and 0x01 in cm, that's to say if the threshold you want is 15cm, you should write a 0x0f(as 0x0f is equal to 15 )into address 0x00 and 0x00 in address 0x01,and never forget that once you change the distance threshold,the sum is also needed to be corrected. Details for the data is in the table below. Briefly, works like this cmd1<cmd, address, data, checksum>

checkSum = Low 8 bit of the sum of command+data0+data1

// # Editor    :Holiday from DFRobot
// # Data      :30.05.2013

// # Product name:ultrasonic scanner 
// # Product SKU:SEN0001
// # Version :  3.2

// # Description:
// # This sample shows how to use the Autonomous trigger mode by writing its EEPROM 

// # Connection:
// #       Pin 1 VCC (URM V3.2) -> VCC (Arduino)
// #       Pin 2 GND (URM V3.2) -> GND (Arduino)
// #       Pin 6 COMP/TRIG (URM V3.2) -> Pin 2 (Arduino)
// #

int cmmd1[]={
  0x44,0x00,0x10,0x54};//low byte stored in the sensor for the distance threshold.
int cmmd2[]={
  0x44,0x01,0x00,0x45};//high byte, write 0x0010 into address 0x01 and 0x00,so the threshold is set to 16cm
int cmmd3[]={
  0x44,0x02,0xaa,0xf0};// Autonomous mode. write 0xaa into address 0x02
//int cmmd3[]={
//  0x44,0x02,0xbb,0x01};  // PWM mode. write 0xbb into address 0x02
int i;

void setup(){                                 
  Serial.begin(9600);                         // Sets the baud rate to 9600
  A_Mode_Setup();                             //PWM mode setup function
}

void loop()
{
}                      

void A_Mode_Setup(){ 
  //write the data into the URM37 EEPROM
  for (i=0;i<4;i++)
    Serial.write(cmmd3[i]);                             
  delay(200);                                           

  for (i=0;i<4;i++)
    Serial.write(cmmd1[i]);
  delay(200);

  for (i=0;i<4;i++)
    Serial.write(cmmd2[i]);
  delay(200);

}

Remember to unplug the serial pins from Arduino before uploading your code.

After the code is uploaded, press reset on your Arduino board to confirm it is written on the module. Then you can connect your sensor with the following wiring system. And just read the pin for changes, when the threshold distance is reached.

TTL Mode Connection Diagram

int pin = 13;
volatile int state = LOW;

void setup(){                                 
  pinMode(pin, OUTPUT);
  attachInterrupt(0, user_diy, CHANGE);          //The ON/OFF switch can be used as a singal of interruption
}

void loop(){
  digitalWrite(pin, state);
}   

void user_diy()              //user can give your own code in this interruput function
{     
  state = !state;
}

Mode 3: PWM passive control mode

Under this mode, a low pull on pin COMP/TRIG will trigger a sensor reading. The width of the pulse is proportional to the servo rotating degree. After a successful sensor reading, Pin PWM will output pulses, every 50us represents 1cm. If the reading is invalid, a 50000us pulse will be returned.

The sketch for PWM passive control mode



// # Editor    :Jiang from DFRobot
// # Data      :18.09.2012

// # Product name:ultrasonic scanner 
// # Product SKU:SEN0001
// # Version :  0.2

// # Description:
// # The Sketch for scanning 180 degree area 4-500cm detecting range

// # Connection:
// #       Pin 1 VCC (URM V3.2) -> VCC (Arduino)
// #       Pin 2 GND (URM V3.2) -> GND (Arduino)
// #       Pin 4 PWM (URM V3.2) -> Pin 3 (Arduino)
// #       Pin 6 COMP/TRIG (URM V3.2) -> Pin 5 (Arduino)
// #
int URPWM = 3; // PWM Output 0-25000US,Every 50US represent 1cm
int URTRIG=5; // PWM trigger pin

unsigned int Distance=0;
uint8_t EnPwmCmd[4]={0x44,0x02,0xbb,0x01};    // distance measure command

void setup(){                                 // Serial initialization
  Serial.begin(9600);                         // Sets the baud rate to 9600
  PWM_Mode_Setup();
}

void loop()
{
 PWM_Mode();
 delay(20);
}                      //PWM mode setup function

void PWM_Mode_Setup(){ 
  pinMode(URTRIG,OUTPUT);                     // A low pull on pin COMP/TRIG
  digitalWrite(URTRIG,HIGH);                  // Set to HIGH
 
  pinMode(URPWM, INPUT);                      // Sending Enable PWM mode command
 
  for(int i=0;i<4;i++){
      Serial.write(EnPwmCmd[i]);
   } 
}

void PWM_Mode(){                              // a low pull on pin COMP/TRIG  triggering a sensor reading
    digitalWrite(URTRIG, LOW);
    digitalWrite(URTRIG, HIGH);               // reading Pin PWM will output pulses
    
    unsigned long DistanceMeasured=pulseIn(URPWM,LOW);
    
    if(DistanceMeasured==50000){              // the reading is invalid.
      Serial.print("Invalid");    
   }
    else{
      Distance=DistanceMeasured/50;           // every 50us low level stands for 1cm
   }
  Serial.print("Distance=");
  Serial.print(Distance);
  Serial.println("cm");
}


PWM Mode Connection Diagram

Serial control protocol

Serial setting:Port rate: 9600; Parity: none; Stop bit: 1

Command: Control command consists of four bits, command+data0+data1+sum. Sum=Low 8 bit of the sum of command+data0+data1.

Command Format Function Description
0x11+NC+NC+Sum (Sample: 0x11 0x00 0x00 0x11) Enable 16 bit temperature reading Reading the temperature, the return data format will be:

0x11+High(temperature)+Low(temperature)+SUM

If the temperature is above 0, the first four bits of High will be all 0. If the temperature is below 0, the first four bits of High will be all 1.

The last 4 bits of High together with the Low bits stands for 12bits temperature. The resolution is 0.1. When the reading is invalid, it returns 0x11+0xFF+0xFF+SUM

0x22+Degree+NC+SUM (Sample: 0x22 0x00 0x00 0x22 ) Enable 16 bit distance reading The degree in the command is used to control a servo motor to rotate corresponding degree.


Degree: 0-46 stands for 0-270 degrees, for example, 3 stands for 18 degrees.
Return data format will be: 0x22+High(distance)+Low(distance)+SUM. When the reading is invalid, it returns 0x22+0xFF+0xFF+SUM

0x33+Add+NC+SUM Enable internal EEPROM reading Return data will be 0x33+Add+Data+SUM.
0x44+Add+Data+SUM (Sample: 0x44 0x02 0xbb 0x01) Enable PWM mode Enable internal EEPROM writing Written data can only from 0-255.

Address 0x00-0x02 is used to configure the mode. 0x00 – threshold distance (Low) 0x01 – threshold distance (High) 0x02 – Operation Mode (0xaa for autonomous mode) (0xbb for PWM passive control mode)

The return data format will be: 0x44+Add+Data+SUM

Note:NC stands for any data,SUM stands for sum, Add stands for address.

1. PWN_ON must be set to High to enable sensor.

Examples: Function to calculate the temperature:

IF(HightByte>=0xF0) 
{ 
Temperature= ((HightByte-0xF0)*256-LowByte)/10
 } 
Else
{ 
Temperature= ((HightByte)*256-LowByte)/10 
}

Servo control command reference table:

DEC 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
HEX 0 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
Degree 0 6 12 18 24 29 35 41 47 53 59 65 70 76 82 88
DEC 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
HEX 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F
Degree 94 100 106 112 117 123 129 135 141 147 153 159 164 170 176 182
DEC 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
HEX 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E
Degree 188 194 200 206 211 217 223 229 235 241 247 252 258 264 270



URM37 V3.2 Ultrasonic Sensor6.png



Figure UMRV3.2 control a servo provides 270 degree scanning area



V3.2 Help Mate Download:





Arduino Sketch

Use a servo to control the position,and the ultrasonic sensor to judge the distance.Here is the sketch.

Ultrasonic_Sensor_Kit


NOTE: Please put the sensor jumpers to TTL mode. See above for a picture indicating TTL mode

	
// # Editor    : Jiang from DFRobot
// # Data      : 24.07.2012

// # Product name:ultrasonic scanner Kit
// # Product SKU:SEN0001
// # Version :  0.2

// # Description:
// # The Sketch for scanning 180 degree area 4-500cm detecting range

// # Connection:
// #       Pin 1 VCC (URM V3.2) -> VCC (Arduino)
// #       Pin 2 GND (URM V3.2) -> GND (Arduino)
// #       Pin 4 PWM (URM V3.2) -> Pin 3 (Arduino)
// #       Pin 6 COMP/TRIG (URM V3.2) -> Pin 5 (Arduino)
// # Pin mode: PWM
// # Working Mode: PWM passive control mode.
// # If it is your first time to use it,please make sure the two jumpers to the right hand
// # side of the device are set to TTL mode. You'll also find a secondary jumper on 
// # the left hand side, you must break this connection or you may damage your device. 

#include <Servo.h>                                  // Include Servo library
Servo myservo;                                      // create servo object to control a servo 

int pos=0;                                          // variable to store the servo position
int URPWM=3;                                        // PWM Output 0-25000us,every 50us represent 1cm
int URTRIG=5;                                       // PWM trigger pin
boolean up=true;                                    // create a boolean variable
unsigned long time;                                 // create a time variable
unsigned long urmTimer = 0;                          // timer for managing the sensor reading flash rate

unsigned int Distance=0;
uint8_t EnPwmCmd[4]={0x44,0x22,0xbb,0x01};          // distance measure command

void setup(){                                      // Serial initialization
  Serial.begin(9600);                              // Sets the baud rate to 9600
  myservo.attach(9);                                // Pin 9 to control servo
  PWM_Mode_Setup();
}

void loop(){   
   if(millis()-time>=20){                           // interval 0.02 seconds
     time=millis();                                 // get the current time of programme
     if(up){                                        // judge the condition
      if(pos>=0 && pos<=179){                   
        pos=pos+1;                                  // in steps of 1 degree 
        myservo.write(pos);                         // tell servo to go to position in variable 'pos' 
      }
      if(pos>179)  up= false;                       // assign the variable again
    }
     else {                                       
      if(pos>=1 && pos<=180){    
        pos=pos-1;
        myservo.write(pos);
      }
      if(pos<1)  up=true;
    }
   }
   
   if(millis()-urmTimer>50){
     urmTimer=millis(); 
     PWM_Mode();
   }
 }

 void PWM_Mode_Setup(){ 
  pinMode(URTRIG,OUTPUT);                            // A low pull on pin COMP/TRIG
  digitalWrite(URTRIG,HIGH);                         // Set to HIGH
 
  pinMode(URPWM, INPUT);                             // Sending Enable PWM mode command
 
  for(int i=0;i<4;i++){
      Serial.write(EnPwmCmd[i]);
   } 
}

void PWM_Mode(){                                     // a low pull on pin COMP/TRIG  triggering a sensor reading
    digitalWrite(URTRIG, LOW); 
    digitalWrite(URTRIG, HIGH);                      // reading Pin PWM will output pulses
    
    unsigned long DistanceMeasured=pulseIn(URPWM,LOW);
    
    if(DistanceMeasured==50000){                     // the reading is invalid.
      Serial.print("Invalid");    
   }
    else{
      Distance=DistanceMeasured/50;                  // every 50us low level stands for 1cm
   }
  Serial.print("Distance=");
  Serial.print(Distance);
  Serial.println("cm");
}


The distance measured

Resources



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