Lesson 35 Intelligent Temperature Measurement System

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Introduction

In this experiment, we will use some modules together to build an intelligent temperature measurement system.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

– 1 * Network cable (or USB wireless network adapter)

– 1 * Active Buzzer

– 1 * RGB LED Module

– 1 * DS18B20 Temperature Sensor

– 1 * PCF8591

– 1 * Joystick PS2

– 2 * 3-Pin anti-reverse cable

– 1 * 4-Pin anti-reverse cable

– 1 * 5-Pin anti-reverse cable

– Several Jumper wires (M to F)

Experimental Principle

It is similar with lesson 26. The only difference is that we can adjust the lower limit and upper limit value by joystick PS2 when programming.

As mentioned previously, joystick PS2 has five operation directions: up, down, left, right and press-down. Well, in this experiment, we will use the left and right directions to control the upper limit value and up/down direction to control the lower limit. If you press down the joystick, the system will log out.

Experimental Procedures

Step 1: Build the circuit

Raspberry PiDS18B20 Module
GPIO7SIG
5VVCC
GNDGND
Raspberry PiPCF8591 ModuleJoystick PS2
SDASDA*
SCLSCL*
3V3VCCVCC
GNDGNDGND
*AIN0Y
*AIN1X
*AIN2Bt
Raspberry PiRGB LED Module
GPIO0R
GPIO1G
GPIO2B
5VVCC
Raspberry PiActive Buzzer Module
GPIO3SIG
3.3VVCC
GNDGND

For C language users:

Step 2: Check the address of your sensor

ls /sys/bus/w1/devices/

It may be like this:

28-031467805fff  w1_bus_master1

Copy or write down 28-XXXXXXX. This is the address of your sensor.

Step 2: Change directory and edit

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/35_expand02/

nano temp_monitor.c

Find the function float tempRead(void), and the line “fd = open(XXXXXX)”. Replace “28-031467805ff” with your sensor address.

float tempRead(void)

{

float temp;

int i, j;

int fd;

int ret;

char buf[BUFSIZE];

char tempBuf[5];

fd = open(“/sys/bus/w1/devices/28-031467805fff/w1_slave”, O_RDONLY);

if(-1 == fd){

perror(“open device file error”);

return 1;

}

Save and exit.

Step 4: Compile

gcc temp_monitor.c -lwiringPi

Step 5Run

sudo ./a.out

For Python users:

Step 2: Change directory

 cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 4: Run

sudo python 35_temp_monitor.py

Now, you can pull the shaft of the joystick left and right to set the upper limit value, and up and down to set the lower limit value. Then, if the ambient temperature reaches the upper limit value or lower limit value, the buzzer will beep in a different frequency to warn.

 C Code

#include <wiringPi.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <pcf8591.h>

#define     LedRed		0
#define     LedGreen	1
#define     LedBlue		2

#define     PCF			120

#define		Beep		3 

#define		BUFSIZE		128

typedef unsigned char uchar;
typedef unsigned int  uint;

static int sys_state = 1; 

static int AIN0 = PCF + 0;
static int AIN1 = PCF + 1;
static int AIN2 = PCF + 2;

void beepInit(void)
{
	pinMode(Beep, OUTPUT);	
}

void beep_on(void)
{
	digitalWrite(Beep, LOW);	
}

void beep_off(void)
{	
	digitalWrite(Beep, HIGH);	
}

void beepCtrl(int t)
{
	beep_on();
	delay(t);
	beep_off();
	delay(t);
}

float tempRead(void)
{
	float temp;
	int i, j;
    int fd;
	int ret;

	char buf[BUFSIZE];
	char tempBuf[5];
	
	fd = open("/sys/bus/w1/devices/28-031467805fff/w1_slave", O_RDONLY);

	if(-1 == fd){
		perror("open device file error");
		return 1;
	}

	while(1){
		ret = read(fd, buf, BUFSIZE);
		if(0 == ret){
			break;	
		}
		if(-1 == ret){
			if(errno == EINTR){
				continue;	
			}
			perror("read()");
			close(fd);
			return 1;
		}
	}

	for(i=0;i<sizeof(buf);i++){
		if(buf[i] == 't'){
			for(j=0;j<sizeof(tempBuf);j++){
				tempBuf[j] = buf[i+2+j]; 	
			}
		}	
	}

	temp = (float)atoi(tempBuf) / 1000;

	close(fd);

	return temp;
}

void ledInit(void)
{
	pinMode(LedRed,   OUTPUT);	
	pinMode(LedGreen, OUTPUT);	
	pinMode(LedBlue,  OUTPUT);	
}

/* */
void ledCtrl(int n, int state)
{
	digitalWrite(n, state);
}

void joystickquit(void)
{
	sys_state = 0;
	printf("interrupt occur !\n");
}

uchar get_joyStick_state(void)
{
	uchar tmp = 0;
	uchar xVal = 0, yVal = 0, zVal = 0;
	
	xVal = analogRead(AIN1);
	if(xVal >= 250){
		tmp = 1;
	}
	if(xVal <= 5){
		tmp = 2;
	}

	yVal = analogRead(AIN0);
	if(yVal >= 250){
		tmp = 4;
	}
	if(yVal <= 5){
		tmp = 3;
	}
	
	zVal = analogRead(AIN2);
	if(zVal <= 5){
		tmp = 5;
	}

	if(xVal-127<30 && xVal-127>-30 && yVal-127<30 && yVal-127>-30 && zVal<127){
		tmp = 0;
	}
// Uncomment this line to see the value of joystick.
//	printf("x = %d, y = %d, z = %d",xVal,yVal,zVal);
	return tmp;
}

int main(void)
{
	int i;
	uchar joyStick = 0;
	float temp;
	uchar low = 26, high = 30;

	if(wiringPiSetup() == -1){
		printf("setup wiringPi failed !");
		return 1; 
	}
	
	pcf8591Setup(PCF, 0x48);
	ledInit();
	beepInit();
	
	printf("System is running...\n");

	while(1){
		flag:
		joyStick = get_joyStick_state();

		switch(joyStick){
			case 1 : --low;  break; 
			case 2 : ++low;  break;
			case 3 : ++high; break;
			case 4 : --high; break;
			case 5 : joystickquit(); break;
			default: break;
		}
		
		if(low >= high){
			printf("Error, lower limit should be less than upper limit\n");
			goto flag;
		}

		printf("The lower limit of temperature : %d\n", low);
		printf("The upper limit of temperature : %d\n", high);
		
		temp = tempRead();
		
		printf("Current temperature : %0.3f\n", temp);
		
		if(temp < low){
			ledCtrl(LedBlue,  LOW);
			ledCtrl(LedRed,   HIGH);
			ledCtrl(LedGreen, LOW);
			for(i = 0;i < 3; i++){
				beepCtrl(400);
			}
		}
		if(temp >= low && temp < high){
			ledCtrl(LedBlue,  HIGH);
			ledCtrl(LedRed,   HIGH);
			ledCtrl(LedGreen, LOW);
		}
		if(temp >= high){
			ledCtrl(LedBlue,  HIGH);
			ledCtrl(LedRed,   LOW);
			ledCtrl(LedGreen, HIGH);
			for(i = 0;i < 3; i++){
				beepCtrl(80);
			}
		}

		if(sys_state == 0){
			ledCtrl(LedRed, LOW);
			ledCtrl(LedGreen, LOW);
			ledCtrl(LedBlue, LOW);
			beep_off();
			printf("SyStem will be off...\n");
			break;
		}
	}
	return 0;
}


Python Code
 

import RPi.GPIO as  GPIO
import importlib
import time
import sys

# BOARD pin numbering
LedR	=	11
LedG	=	12
LedB	=	13
Buzz	=	15

#ds18b20 = '28-031467805fff'
#location = '/sys/bus/w1/devices/' + ds18b20 + '/w1_slave'

joystick	=	importlib.import_module('15_joystick_PS2')
ds18b20		=	importlib.import_module('26_ds18b20')
beep		=	importlib.import_module('10_active_buzzer')
rgb			=	importlib.import_module('02_rgb_led')

joystick.setup()
ds18b20.setup()
beep.setup(Buzz)
rgb.setup(LedR, LedG, LedB)

color = {'Red':0xFF0000, 'Green':0x00FF00, 'Blue':0x0000FF}

def setup():
	global lowl, highl
	lowl = 29
	highl = 31

def edge():
	global lowl, highl
	temp = joystick.direction()
	if temp == 'Pressed':
		destroy()
		quit()
	if temp == 'up' and lowl < highl-1:
		highl += 1
	if temp == 'down' and lowl >= -5:
		highl -= 1
	if temp == 'right' and highl <= 125:
		lowl += 1
	if temp == 'left' and lowl < highl-1:
		lowl -= 1

def loop():
	while True:
		edge()
		temp = ds18b20.read()
		print 'The lower limit of temperature : ', lowl
		print 'The upper limit of temperature : ', highl
		print 'Current temperature : ', temp
		if float(temp) < float(lowl):
			rgb.setColor(color['Blue'])
			for i in range(0, 3):
				beep.beep(0.5)
		if temp >= float(lowl) and temp < float(highl):
			rgb.setColor(color['Green'])
		if temp >= float(highl):
			rgb.setColor(color['Red'])
			for i in range(0, 3):
				beep.beep(0.1)

def destroy():
	beep.destroy()
	joystick.destroy()
	ds18b20.destroy()
	rgb.destroy()
	GPIO.cleanup()

if __name__ == "__main__":
	try:
		setup()
		loop()
	except KeyboardInterrupt:
		destroy()