Hi
I would like to read the temperature values of 16 different points with Arduino, a 16-channel multiplexer (CD74HC4067) and MAX-6675 k-type thermocouple.
I have used MAX6675 and CD74HC4067 separately before, but this is the first time I have used both.
Circuit drawing is as follows:
I made all the necessary connections of the 16 channel multiplexer to Arduino and connected the signal (COM) port to the plus input port of MAX6675.
I made all the connections of MAX6675 as shown.
What I want to do is this;
I want the multiplexer to send the analog value to MAX6675 by changing the read address for each temperature value. In this way, I want to read the temperature value over MAX6675. But when I read it over MAX6675 it doesn't get any value. I get zero.
My Arduino codes are as follows.
#include <Mux.h>
#include <max6675.h>
Mux mux;
//Mux control pins
int s0 = 6;
int s1 = 7;
int s2 = 8;
int s3 = 9;
int thermoDO = 12;
int thermoCS = 10;
int thermoCLK = 13;
MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);
//Mux in "SIG" pin
int SIG_pin = 0;
void setup(){
pinMode(s0, INPUT);
pinMode(s1, INPUT);
pinMode(s2, INPUT);
pinMode(s3, INPUT);
pinMode(thermoCS, OUTPUT);
pinMode(thermoDO, INPUT);
pinMode(thermoCLK, OUTPUT);
digitalWrite(s0, HIGH);
digitalWrite(s1, HIGH);
digitalWrite(s2, HIGH);
digitalWrite(s3, HIGH);
Serial.begin(9600);
mux.setup(s0,s1,s2,s3,SIG_pin); // initialise on setup
}
void loop(){
for(int i = 0; i < 16; i ++){
Serial.print(i);
Serial.print(" = ");
Serial.println(readMux(i));
}
delay(1000);
}
int readMux(int channel){
int controlPin[] = {s0, s1, s2, s3};
int muxChannel[16][4]={
{0,0,0,0}, //channel 0
{1,0,0,0}, //channel 1
{0,1,0,0}, //channel 2
{1,1,0,0}, //channel 3
{0,0,1,0}, //channel 4
{1,0,1,0}, //channel 5
{0,1,1,0}, //channel 6
{1,1,1,0}, //channel 7
{0,0,0,1}, //channel 8
{1,0,0,1}, //channel 9
{0,1,0,1}, //channel 10
{1,1,0,1}, //channel 11
{0,0,1,1}, //channel 12
{1,0,1,1}, //channel 13
{0,1,1,1}, //channel 14
{1,1,1,1} //channel 15
};
//loop through the 4 sig
for(int i = 0; i < 4; i ++){
digitalWrite(controlPin[i], muxChannel[channel][i]);
}
//read the value at the SIG pin
//int val = digitalRead(SIG_pin); // It's doesn't work
//int val = analogRead(SIG_pin); // It's doesn't work
int val = thermocouple.readCelsius();
//return the value
return val;
}
Can you help me solve my problem?
If you have suggestions about circuit drawing and codes, I would be pleased to hear, do not hesitate.
Thank you so much.
It has been suggested you might use relays but even that requires great design care.