Temperatur

Temperatursensor.

DS18B20

Innehåll.

Tillbaka till Raspbery Pi
Inledning.
Installation.
C-program.
MySQL.
Support/Hjälp.
Referens.

Inledning.

Installation.

Koppla in DS18B20 som nedanstående bild visar.

Kör kommandona:
sudo modprobe w1-gpio
sudo modprobe w1-therm

sudo nano /boot/config.txt
Lägg till följande sist i filen:
dtoverlay=w1-gpio
Kör kommando:
sudo reboot

Till början.

C-program.

Kompilera programmet: gcc -Wall -std=gnu99 wt.c -o wt
Exekvera programmet: ./wt
Avbryt programmet med: ctrl-c

/****************************************************** * w1-v2.c * * Kompilera: gcc -Wall -std=gnu99 w1-v2.c -o w1-v2 * Exekvera: ./w1-v2 * ******************************************************/ #include <stdio.h> #include <dirent.h> #include <string.h> #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdint.h> #include <time.h> int main (void) { DIR *dir; struct dirent *dirent; char dev[16]; // Dev ID char devPath[128]; // Path to device char buf[256]; // Data from device char tmpData[6]; // Temp C * 1000 reported by device char path[] = "/sys/bus/w1/devices"; ssize_t numRead; time_t curtime; struct tm *loctime; char timebuffer[40]; /* Get the current time. */ curtime = time (NULL); /* Convert it to local time representation. */ loctime = localtime (&curtime); FILE *fp; dir = opendir (path); if (dir != NULL) { while ((dirent = readdir (dir))) // 1-wire devices are links beginning with 28- if (dirent->d_type == DT_LNK && strstr(dirent->d_name, "28-") != NULL) { strcpy(dev, dirent->d_name); printf("\nDevice: %s\n", dev); } (void) closedir (dir); } else { perror ("Couldn't open the w1 devices directory"); return 1; } // Assemble path to OneWire device sprintf(devPath, "%s/%s/w1_slave", path, dev); // Read temp continuously // Opening the device's file triggers new reading while(1) { int fd = open(devPath, O_RDONLY); if(fd == -1) { perror ("Couldn't open the w1 device."); return 1; } while((numRead = read(fd, buf, 256)) > 0) { strncpy(tmpData, strstr(buf, "t=") + 2, 5); float tempC = strtof(tmpData, NULL); printf("Device: %s - ", dev); printf("Temp: %.3f C ", tempC / 1000); printf("%.3f F\n\n", (tempC / 1000) * 9 / 5 + 32); strftime(timebuffer,40,"%Y-%m-%d %H:%M",loctime); fp=fopen("/home/pi/Documents/Data/temp3.txt", "a+"); fprintf(fp,"%s %.2f\n",timebuffer,tempC/1000); fclose(fp); } close(fd); sleep(60); } return 0; }

Resultat.

Här är ett modifierat program som laddar in data i en MySQL-databas.
Kompilera programmet med: gcc -Wall -std=gnu99 -L/lib64/mysql -lmysqlclient w1-v3.c -o w1-v3
Exekvera med: ./w1-v3

/******************************************************
 * w1-v3.c
 * 
 * 2016-08-07
 * Kompilera: gcc -Wall -std=gnu99 -L/lib64/mysql -lmysqlclient w1-v3.c -o w1-v3
 * Exekvera: ./w1-v3
 * 
 ******************************************************/
 
#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <time.h>
#include </usr/include/mysql/mysql.h>

void insert_data(char day[40],float temperatur);     
     
int main (void) {
 DIR *dir;
 struct dirent *dirent;
 char dev[16];      // Dev ID
 char devPath[128]; // Path to device
 char buf[256];     // Data from device
 char tmpData[6];   // Temp C * 1000 reported by device 
 char path[] = "/sys/bus/w1/devices"; 
 ssize_t numRead;
 time_t curtime;
 struct tm *loctime;
 char timebuffer[40];
 
 	/* Get the current time.  */
	curtime = time (NULL);
	/* Convert it to local time representation.  */
	loctime = localtime (&curtime);
	FILE *fp;
	
 dir = opendir (path);
 if (dir != NULL) {
  while ((dirent = readdir (dir)))
   // 1-wire devices are links beginning with 28-
   if (dirent->d_type == DT_LNK && strstr(dirent->d_name, "28-") != NULL) { 
    strcpy(dev, dirent->d_name);
    //printf("\nDevice: %s\n", dev);
   }
   (void) closedir (dir);
 }
 else {
  perror ("Couldn't open the w1 devices directory");
  return 1;
 }

// Assemble path to OneWire device
 sprintf(devPath, "%s/%s/w1_slave", path, dev);
 // Read temp continuously
 // Opening the device's file triggers new reading
// while(1) {
  int fd = open(devPath, O_RDONLY);
  if(fd == -1) {
   perror ("Couldn't open the w1 device.");
   return 1;   
  }
  while((numRead = read(fd, buf, 256)) > 0) 
  {
   strncpy(tmpData, strstr(buf, "t=") + 2, 5); 
   float tempC = strtof(tmpData, NULL);
   //printf("Device: %s  - ", dev); 
   //printf("Temp: %.3f C  ", tempC / 1000);
   //printf("%.3f F\n\n", (tempC / 1000) * 9 / 5 + 32);
   
   strftime(timebuffer,40,"%Y-%m-%d %H:%M",loctime);
   fp=fopen("/home/pi/Documents/Data/temp4.txt", "a+");
   fprintf(fp,"%s %.2f\n",timebuffer,tempC/1000);
   fclose(fp);
   insert_data(timebuffer,tempC/1000);
  }
  close(fd);
  
// } 
  return 0;
}

void insert_data(char day[40], float temperatur){
  MYSQL *conn;

FILE *fp;

char *server = "localhost";
  char *user = "root";
  char *password = "lösenord"; /* sätt lösenordet för root först. Ange detta här. */
  char *database = "temperatur";

char dag[11];
  char tid[6];
  char temp[5];

char sql[256]="INSERT INTO temp(datum,tid,temp) VALUES(";
  char sqlquery[256];
  
  int postnr;
  char oldtid[6];
  
  conn = mysql_init(NULL);
   
  if (mysql_real_connect(conn, server, user, password, database, 0, NULL, 0) == NULL) {
         fprintf(stderr, "%s\n", mysql_error(conn));
         mysql_close(conn);
         exit(1);
  }

fp=fopen("/home/pi/Documents/Data/temp4.txt", "r");
  postnr=0;
  while (!feof(fp)){
	fseek(fp,0,SEEK_CUR); //offset = 0 för textfiler.
	fscanf(fp,"%s %s %s",dag,tid,temp);
	if(strcmp(tid,oldtid) != 0){
		postnr++;
		strcpy(sqlquery,sql);
		strcat(sqlquery,"'");
		strcat(sqlquery,dag);
		strcat(sqlquery,"'");
		strcat(sqlquery,",'");
		strcat(sqlquery,tid);
		strcat(sqlquery,"'");
		strcat(sqlquery,",");
		strcat(sqlquery,temp);
		strcat(sqlquery,")");
	
		printf("sqlquery = %s\n",sqlquery);

if(mysql_query(conn,sqlquery)){
			fprintf(stderr,"%s\n",mysql_error(conn));
			mysql_close(conn);
			exit(1);
		}
	}
	strcpy(oldtid,tid);
  }		
  mysql_close(conn);
  sleep(6);
  system("rm /home/pi/Documents/Data/temp4.txt");
}

Till början.

MySQL-kommandon.

Sätt behörigheten på mappen Data till chmod +777 Data.
Kommandosekvens för att skriva ut tabellen temperatur i en textfil.:
mysql -u pi -p;
use temperatur;
SELECT * FROM temp INTO OUTFILE '/home/pi/Documents/Data/temperatur.txt';

Resultat.

Support/Hjälp.

Jag har upptäckt att kabeln till DS18B20 verkar vara för tjock för att leda ut mellan fönster och fönsterkarm. Den kläms så mycket att de inre kardelerna skavs så hårt mot varandra att isoleringen skadas på något sätt, på ett sätt som gör att resultaten blir felaktiga.
Exempel på felaktiga resultat:

Sista raden är resultatet när kabeln tagits bort från fönstret.

Till början.

Referens.

Kjell & Co.
electro:kit

Till början.

Erfarenheter av DS18B20 sensor.