Lesson 14 Temperature Monitoring and Alarm

Introduction

In this lesson, we will use a thermistor and a buzzer to make a temperature monitoring and alarm system.

Experimental Conditions

– 1*Raspberry Pi

– 1*Breadboard

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

– 1*Thermistor

– 1*Buzzer

– 1*NPN transistor (8050)

– 1*Resistor (1KΩ)

– 1*Resistor (10KΩ)

– 1*ADC0832

– Jumper wires

Experimental Principle

We use an ADC0832 to convert the analog temperature collected by the thermistor to digital temperature. When the result is greater than 200 degrees Celsius, the buzzer will alarm.

Experimental Procedures

Step 1: Connect the circuit

Step 2: Edit and save the code(see path/Rpi_LcdStartKit/14_tempMonitor/ tempMonitor.c)

Step 3: Compile the code

gcc  tempMonitor.c  -lwiringPi

Step 4: Run the program

./a.out

Press Enter, if use a lighter to burn the thermistor, you will hear the buzzer alarm.

Code

#include <wiringPi.h> #include <stdio.h> typedef unsigned char uchar; typedef unsigned int uint; #define ADC_CS 0 #define ADC_CLK 1 #define ADC_DIO 2 #define Beep 3 void beepInit(void) { pinMode(Beep, OUTPUT); digitalWrite(Beep, 0); } void beep(void) { digitalWrite(Beep, 1); delay(200); digitalWrite(Beep, 0); delay(200); } uchar get_ADC_Result(void) { //10:CH0 //11:CH1 uchar i; uchar dat1=0, dat2=0; digitalWrite(ADC_CS, 0); digitalWrite(ADC_CLK,0); digitalWrite(ADC_DIO,1); delayMicroseconds(2); digitalWrite(ADC_CLK,1); delayMicroseconds(2); digitalWrite(ADC_CLK,0); digitalWrite(ADC_DIO,1); delayMicroseconds(2); //CH0 10 digitalWrite(ADC_CLK,1); delayMicroseconds(2); digitalWrite(ADC_CLK,0); digitalWrite(ADC_DIO,0); delayMicroseconds(2); //CH0 0 digitalWrite(ADC_CLK,1); digitalWrite(ADC_DIO,1); delayMicroseconds(2); digitalWrite(ADC_CLK,0); digitalWrite(ADC_DIO,1); delayMicroseconds(2); for(i=0;i<8;i++) { digitalWrite(ADC_CLK,1); delayMicroseconds(2); digitalWrite(ADC_CLK,0); delayMicroseconds(2); pinMode(ADC_DIO, INPUT); dat1=dat1<<1 | digitalRead(ADC_DIO); } for(i=0;i<8;i++) { dat2 = dat2 | ((uchar)(digitalRead(ADC_DIO))<<i); digitalWrite(ADC_CLK,1); delayMicroseconds(2); digitalWrite(ADC_CLK,0); delayMicroseconds(2); } digitalWrite(ADC_CS,1); pinMode(ADC_DIO, OUTPUT); return(dat1==dat2) ? dat1 : 0; } int main(void) { uchar adcVal; if(wiringPiSetup() == -1){ printf(“setup wiringPi failed !”); return 1; } pinMode(ADC_CS, OUTPUT); pinMode(ADC_CLK, OUTPUT); beepInit(); while(1){ pinMode(ADC_DIO, OUTPUT); adcVal = get_ADC_Result(); printf(“adcval : %d\n”,adcVal); if(adcVal > 200){ beep(); } } return 0; }